From: Ryan Roberts <ryan.roberts@arm.com>
Whenever vmalloc allocates high order pages (e.g. for a huge mapping) it
must immediately split_page() to order-0 so that it remains compatible
with users that want to access the underlying struct page.
Commit a06157804399 ("mm/vmalloc: request large order pages from buddy
allocator") recently made it much more likely for vmalloc to allocate
high order pages which are subsequently split to order-0.
Unfortunately this had the side effect of causing performance
regressions for tight vmalloc/vfree loops (e.g. test_vmalloc.ko
benchmarks). See Closes: tag. This happens because the high order pages
must be gotten from the buddy but then because they are split to
order-0, when they are freed they are freed to the order-0 pcp.
Previously allocation was for order-0 pages so they were recycled from
the pcp.
It would be preferable if when vmalloc allocates an (e.g.) order-3 page
that it also frees that order-3 page to the order-3 pcp, then the
regression could be removed.
So let's do exactly that; use the new __free_contig_range() API to
batch-free contiguous ranges of pfns. This not only removes the
regression, but significantly improves performance of vfree beyond the
baseline.
A selection of test_vmalloc benchmarks running on arm64 server class
system. mm-new is the baseline. Commit a06157804399 ("mm/vmalloc: request
large order pages from buddy allocator") was added in v6.19-rc1 where we
see regressions. Then with this change performance is much better. (>0
is faster, <0 is slower, (R)/(I) = statistically significant
Regression/Improvement):
+-----------------+----------------------------------------------------------+-------------------+--------------------+
| Benchmark | Result Class | mm-new | this series |
+=================+==========================================================+===================+====================+
| micromm/vmalloc | fix_align_alloc_test: p:1, h:0, l:500000 (usec) | 1331843.33 | (I) 67.17% |
| | fix_size_alloc_test: p:1, h:0, l:500000 (usec) | 415907.33 | -5.14% |
| | fix_size_alloc_test: p:4, h:0, l:500000 (usec) | 755448.00 | (I) 53.55% |
| | fix_size_alloc_test: p:16, h:0, l:500000 (usec) | 1591331.33 | (I) 57.26% |
| | fix_size_alloc_test: p:16, h:1, l:500000 (usec) | 1594345.67 | (I) 68.46% |
| | fix_size_alloc_test: p:64, h:0, l:100000 (usec) | 1071826.00 | (I) 79.27% |
| | fix_size_alloc_test: p:64, h:1, l:100000 (usec) | 1018385.00 | (I) 84.17% |
| | fix_size_alloc_test: p:256, h:0, l:100000 (usec) | 3970899.67 | (I) 77.01% |
| | fix_size_alloc_test: p:256, h:1, l:100000 (usec) | 3821788.67 | (I) 89.44% |
| | fix_size_alloc_test: p:512, h:0, l:100000 (usec) | 7795968.00 | (I) 82.67% |
| | fix_size_alloc_test: p:512, h:1, l:100000 (usec) | 6530169.67 | (I) 118.09% |
| | full_fit_alloc_test: p:1, h:0, l:500000 (usec) | 626808.33 | -0.98% |
| | kvfree_rcu_1_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 532145.67 | -1.68% |
| | kvfree_rcu_2_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 537032.67 | -0.96% |
| | long_busy_list_alloc_test: p:1, h:0, l:500000 (usec) | 8805069.00 | (I) 74.58% |
| | pcpu_alloc_test: p:1, h:0, l:500000 (usec) | 500824.67 | 4.35% |
| | random_size_align_alloc_test: p:1, h:0, l:500000 (usec) | 1637554.67 | (I) 76.99% |
| | random_size_alloc_test: p:1, h:0, l:500000 (usec) | 4556288.67 | (I) 72.23% |
| | vm_map_ram_test: p:1, h:0, l:500000 (usec) | 107371.00 | -0.70% |
+-----------------+----------------------------------------------------------+-------------------+--------------------+
Fixes: a06157804399 ("mm/vmalloc: request large order pages from buddy allocator")
Closes: https://lore.kernel.org/all/66919a28-bc81-49c9-b68f-dd7c73395a0d@arm.com/
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Co-developed-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>
---
Changes since v2:
- Remove BUG_ON in favour of simple implementation as this has never
been seen to output any bug in the past as well
- Move the free loop to separate function, free_pages_bulk()
- Update stats, lruvec_stat in separate loop
Changes since v1:
- Rebase on mm-new
- Rerun benchmarks
Made-with: Cursor
---
include/linux/gfp.h | 2 ++
mm/page_alloc.c | 23 +++++++++++++++++++++++
mm/vmalloc.c | 16 +++++-----------
3 files changed, 30 insertions(+), 11 deletions(-)
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 7c1f9da7c8e56..71f9097ab99a0 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -239,6 +239,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
struct page **page_array);
#define __alloc_pages_bulk(...) alloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))
+void free_pages_bulk(struct page **page_array, unsigned long nr_pages);
+
unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,
unsigned long nr_pages,
struct page **page_array);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index eedce9a30eb7e..250cc07e547b8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5175,6 +5175,29 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
}
EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);
+void free_pages_bulk(struct page **page_array, unsigned long nr_pages)
+{
+ unsigned long start_pfn = 0, pfn;
+ unsigned long i, nr_contig = 0;
+
+ for (i = 0; i < nr_pages; i++) {
+ pfn = page_to_pfn(page_array[i]);
+ if (!nr_contig) {
+ start_pfn = pfn;
+ nr_contig = 1;
+ } else if (start_pfn + nr_contig != pfn) {
+ __free_contig_range(start_pfn, nr_contig);
+ start_pfn = pfn;
+ nr_contig = 1;
+ cond_resched();
+ } else {
+ nr_contig++;
+ }
+ }
+ if (nr_contig)
+ __free_contig_range(start_pfn, nr_contig);
+}
+
/*
* This is the 'heart' of the zoned buddy allocator.
*/
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index c607307c657a6..e9b3d6451e48b 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3459,19 +3459,13 @@ void vfree(const void *addr)
if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS))
vm_reset_perms(vm);
- for (i = 0; i < vm->nr_pages; i++) {
- struct page *page = vm->pages[i];
- BUG_ON(!page);
- /*
- * High-order allocs for huge vmallocs are split, so
- * can be freed as an array of order-0 allocations
- */
- if (!(vm->flags & VM_MAP_PUT_PAGES))
- mod_lruvec_page_state(page, NR_VMALLOC, -1);
- __free_page(page);
- cond_resched();
+ if (!(vm->flags & VM_MAP_PUT_PAGES)) {
+ for (i = 0; i < vm->nr_pages; i++)
+ mod_lruvec_page_state(vm->pages[i], NR_VMALLOC, -1);
}
+ free_pages_bulk(vm->pages, vm->nr_pages);
+
kvfree(vm->pages);
kfree(vm);
}
--
2.47.3On 3/24/26 14:35, Muhammad Usama Anjum wrote:
> From: Ryan Roberts <ryan.roberts@arm.com>
>
> Whenever vmalloc allocates high order pages (e.g. for a huge mapping) it
> must immediately split_page() to order-0 so that it remains compatible
> with users that want to access the underlying struct page.
> Commit a06157804399 ("mm/vmalloc: request large order pages from buddy
> allocator") recently made it much more likely for vmalloc to allocate
> high order pages which are subsequently split to order-0.
>
> Unfortunately this had the side effect of causing performance
> regressions for tight vmalloc/vfree loops (e.g. test_vmalloc.ko
> benchmarks). See Closes: tag. This happens because the high order pages
> must be gotten from the buddy but then because they are split to
> order-0, when they are freed they are freed to the order-0 pcp.
> Previously allocation was for order-0 pages so they were recycled from
> the pcp.
>
> It would be preferable if when vmalloc allocates an (e.g.) order-3 page
> that it also frees that order-3 page to the order-3 pcp, then the
> regression could be removed.
>
> So let's do exactly that; use the new __free_contig_range() API to
> batch-free contiguous ranges of pfns. This not only removes the
> regression, but significantly improves performance of vfree beyond the
> baseline.
>
> A selection of test_vmalloc benchmarks running on arm64 server class
> system. mm-new is the baseline. Commit a06157804399 ("mm/vmalloc: request
> large order pages from buddy allocator") was added in v6.19-rc1 where we
> see regressions. Then with this change performance is much better. (>0
> is faster, <0 is slower, (R)/(I) = statistically significant
> Regression/Improvement):
>
> +-----------------+----------------------------------------------------------+-------------------+--------------------+
> | Benchmark | Result Class | mm-new | this series |
> +=================+==========================================================+===================+====================+
> | micromm/vmalloc | fix_align_alloc_test: p:1, h:0, l:500000 (usec) | 1331843.33 | (I) 67.17% |
> | | fix_size_alloc_test: p:1, h:0, l:500000 (usec) | 415907.33 | -5.14% |
> | | fix_size_alloc_test: p:4, h:0, l:500000 (usec) | 755448.00 | (I) 53.55% |
> | | fix_size_alloc_test: p:16, h:0, l:500000 (usec) | 1591331.33 | (I) 57.26% |
> | | fix_size_alloc_test: p:16, h:1, l:500000 (usec) | 1594345.67 | (I) 68.46% |
> | | fix_size_alloc_test: p:64, h:0, l:100000 (usec) | 1071826.00 | (I) 79.27% |
> | | fix_size_alloc_test: p:64, h:1, l:100000 (usec) | 1018385.00 | (I) 84.17% |
> | | fix_size_alloc_test: p:256, h:0, l:100000 (usec) | 3970899.67 | (I) 77.01% |
> | | fix_size_alloc_test: p:256, h:1, l:100000 (usec) | 3821788.67 | (I) 89.44% |
> | | fix_size_alloc_test: p:512, h:0, l:100000 (usec) | 7795968.00 | (I) 82.67% |
> | | fix_size_alloc_test: p:512, h:1, l:100000 (usec) | 6530169.67 | (I) 118.09% |
> | | full_fit_alloc_test: p:1, h:0, l:500000 (usec) | 626808.33 | -0.98% |
> | | kvfree_rcu_1_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 532145.67 | -1.68% |
> | | kvfree_rcu_2_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 537032.67 | -0.96% |
> | | long_busy_list_alloc_test: p:1, h:0, l:500000 (usec) | 8805069.00 | (I) 74.58% |
> | | pcpu_alloc_test: p:1, h:0, l:500000 (usec) | 500824.67 | 4.35% |
> | | random_size_align_alloc_test: p:1, h:0, l:500000 (usec) | 1637554.67 | (I) 76.99% |
> | | random_size_alloc_test: p:1, h:0, l:500000 (usec) | 4556288.67 | (I) 72.23% |
> | | vm_map_ram_test: p:1, h:0, l:500000 (usec) | 107371.00 | -0.70% |
> +-----------------+----------------------------------------------------------+-------------------+--------------------+
>
> Fixes: a06157804399 ("mm/vmalloc: request large order pages from buddy allocator")
> Closes: https://lore.kernel.org/all/66919a28-bc81-49c9-b68f-dd7c73395a0d@arm.com/
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> Co-developed-by: Muhammad Usama Anjum <usama.anjum@arm.com>
> Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>
> ---
> Changes since v2:
> - Remove BUG_ON in favour of simple implementation as this has never
> been seen to output any bug in the past as well
> - Move the free loop to separate function, free_pages_bulk()
> - Update stats, lruvec_stat in separate loop
>
> Changes since v1:
> - Rebase on mm-new
> - Rerun benchmarks
>
> Made-with: Cursor
> ---
> include/linux/gfp.h | 2 ++
> mm/page_alloc.c | 23 +++++++++++++++++++++++
> mm/vmalloc.c | 16 +++++-----------
> 3 files changed, 30 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 7c1f9da7c8e56..71f9097ab99a0 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -239,6 +239,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
> struct page **page_array);
> #define __alloc_pages_bulk(...) alloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))
>
> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages);
> +
> unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,
> unsigned long nr_pages,
> struct page **page_array);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index eedce9a30eb7e..250cc07e547b8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5175,6 +5175,29 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
> }
> EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);
>
Can we add some kerneldoc describing call context etc?
> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages)
> +{
> + unsigned long start_pfn = 0, pfn;
> + unsigned long i, nr_contig = 0;
> +
> + for (i = 0; i < nr_pages; i++) {
> + pfn = page_to_pfn(page_array[i]);
> + if (!nr_contig) {
> + start_pfn = pfn;
> + nr_contig = 1;
> + } else if (start_pfn + nr_contig != pfn) {
> + __free_contig_range(start_pfn, nr_contig);
> + start_pfn = pfn;
> + nr_contig = 1;
> + cond_resched();
> + } else {
> + nr_contig++;
> + }
> + }
Could we use num_pages_contiguous() here?
while (nr_pages) {
unsigned long nr_contig_pages = num_pages_contiguous(page_array, nr_pages);
__free_contig_range(pfn_to_page(*page_array), nr_contig_pages);
nr_pages -= nr_contig;
page_array += nr_contig;
cond_resched();
}
Something like that?
> + if (nr_contig)
> + __free_contig_range(start_pfn, nr_contig);
> +}
> +
> /*
> * This is the 'heart' of the zoned buddy allocator.
> */
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index c607307c657a6..e9b3d6451e48b 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3459,19 +3459,13 @@ void vfree(const void *addr)
>
> if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS))
> vm_reset_perms(vm);
> - for (i = 0; i < vm->nr_pages; i++) {
> - struct page *page = vm->pages[i];
>
> - BUG_ON(!page);
> - /*
> - * High-order allocs for huge vmallocs are split, so
> - * can be freed as an array of order-0 allocations
> - */
> - if (!(vm->flags & VM_MAP_PUT_PAGES))
> - mod_lruvec_page_state(page, NR_VMALLOC, -1);
> - __free_page(page);
> - cond_resched();
> + if (!(vm->flags & VM_MAP_PUT_PAGES)) {
> + for (i = 0; i < vm->nr_pages; i++)
> + mod_lruvec_page_state(vm->pages[i], NR_VMALLOC, -1);
> }
> + free_pages_bulk(vm->pages, vm->nr_pages);
> +
> kvfree(vm->pages);
> kfree(vm);
> }
--
Cheers,
David
On 25/03/2026 10:05 am, David Hildenbrand (Arm) wrote:
> On 3/24/26 14:35, Muhammad Usama Anjum wrote:
>> From: Ryan Roberts <ryan.roberts@arm.com>
>>
>> Whenever vmalloc allocates high order pages (e.g. for a huge mapping) it
>> must immediately split_page() to order-0 so that it remains compatible
>> with users that want to access the underlying struct page.
>> Commit a06157804399 ("mm/vmalloc: request large order pages from buddy
>> allocator") recently made it much more likely for vmalloc to allocate
>> high order pages which are subsequently split to order-0.
>>
>> Unfortunately this had the side effect of causing performance
>> regressions for tight vmalloc/vfree loops (e.g. test_vmalloc.ko
>> benchmarks). See Closes: tag. This happens because the high order pages
>> must be gotten from the buddy but then because they are split to
>> order-0, when they are freed they are freed to the order-0 pcp.
>> Previously allocation was for order-0 pages so they were recycled from
>> the pcp.
>>
>> It would be preferable if when vmalloc allocates an (e.g.) order-3 page
>> that it also frees that order-3 page to the order-3 pcp, then the
>> regression could be removed.
>>
>> So let's do exactly that; use the new __free_contig_range() API to
>> batch-free contiguous ranges of pfns. This not only removes the
>> regression, but significantly improves performance of vfree beyond the
>> baseline.
>>
>> A selection of test_vmalloc benchmarks running on arm64 server class
>> system. mm-new is the baseline. Commit a06157804399 ("mm/vmalloc: request
>> large order pages from buddy allocator") was added in v6.19-rc1 where we
>> see regressions. Then with this change performance is much better. (>0
>> is faster, <0 is slower, (R)/(I) = statistically significant
>> Regression/Improvement):
>>
>> +-----------------+----------------------------------------------------------+-------------------+--------------------+
>> | Benchmark | Result Class | mm-new | this series |
>> +=================+==========================================================+===================+====================+
>> | micromm/vmalloc | fix_align_alloc_test: p:1, h:0, l:500000 (usec) | 1331843.33 | (I) 67.17% |
>> | | fix_size_alloc_test: p:1, h:0, l:500000 (usec) | 415907.33 | -5.14% |
>> | | fix_size_alloc_test: p:4, h:0, l:500000 (usec) | 755448.00 | (I) 53.55% |
>> | | fix_size_alloc_test: p:16, h:0, l:500000 (usec) | 1591331.33 | (I) 57.26% |
>> | | fix_size_alloc_test: p:16, h:1, l:500000 (usec) | 1594345.67 | (I) 68.46% |
>> | | fix_size_alloc_test: p:64, h:0, l:100000 (usec) | 1071826.00 | (I) 79.27% |
>> | | fix_size_alloc_test: p:64, h:1, l:100000 (usec) | 1018385.00 | (I) 84.17% |
>> | | fix_size_alloc_test: p:256, h:0, l:100000 (usec) | 3970899.67 | (I) 77.01% |
>> | | fix_size_alloc_test: p:256, h:1, l:100000 (usec) | 3821788.67 | (I) 89.44% |
>> | | fix_size_alloc_test: p:512, h:0, l:100000 (usec) | 7795968.00 | (I) 82.67% |
>> | | fix_size_alloc_test: p:512, h:1, l:100000 (usec) | 6530169.67 | (I) 118.09% |
>> | | full_fit_alloc_test: p:1, h:0, l:500000 (usec) | 626808.33 | -0.98% |
>> | | kvfree_rcu_1_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 532145.67 | -1.68% |
>> | | kvfree_rcu_2_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 537032.67 | -0.96% |
>> | | long_busy_list_alloc_test: p:1, h:0, l:500000 (usec) | 8805069.00 | (I) 74.58% |
>> | | pcpu_alloc_test: p:1, h:0, l:500000 (usec) | 500824.67 | 4.35% |
>> | | random_size_align_alloc_test: p:1, h:0, l:500000 (usec) | 1637554.67 | (I) 76.99% |
>> | | random_size_alloc_test: p:1, h:0, l:500000 (usec) | 4556288.67 | (I) 72.23% |
>> | | vm_map_ram_test: p:1, h:0, l:500000 (usec) | 107371.00 | -0.70% |
>> +-----------------+----------------------------------------------------------+-------------------+--------------------+
>>
>> Fixes: a06157804399 ("mm/vmalloc: request large order pages from buddy allocator")
>> Closes: https://lore.kernel.org/all/66919a28-bc81-49c9-b68f-dd7c73395a0d@arm.com/
>> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
>> Co-developed-by: Muhammad Usama Anjum <usama.anjum@arm.com>
>> Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>
>> ---
>> Changes since v2:
>> - Remove BUG_ON in favour of simple implementation as this has never
>> been seen to output any bug in the past as well
>> - Move the free loop to separate function, free_pages_bulk()
>> - Update stats, lruvec_stat in separate loop
>>
>> Changes since v1:
>> - Rebase on mm-new
>> - Rerun benchmarks
>>
>> Made-with: Cursor
>> ---
>> include/linux/gfp.h | 2 ++
>> mm/page_alloc.c | 23 +++++++++++++++++++++++
>> mm/vmalloc.c | 16 +++++-----------
>> 3 files changed, 30 insertions(+), 11 deletions(-)
>>
>> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
>> index 7c1f9da7c8e56..71f9097ab99a0 100644
>> --- a/include/linux/gfp.h
>> +++ b/include/linux/gfp.h
>> @@ -239,6 +239,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
>> struct page **page_array);
>> #define __alloc_pages_bulk(...) alloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))
>>
>> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages);
>> +
>> unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,
>> unsigned long nr_pages,
>> struct page **page_array);
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index eedce9a30eb7e..250cc07e547b8 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -5175,6 +5175,29 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
>> }
>> EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);
>>
>
> Can we add some kerneldoc describing call context etc?
Yes, I'll add short kerneldoc here.
>
>> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages)
>> +{
>> + unsigned long start_pfn = 0, pfn;
>> + unsigned long i, nr_contig = 0;
>> +
>> + for (i = 0; i < nr_pages; i++) {
>> + pfn = page_to_pfn(page_array[i]);
>> + if (!nr_contig) {
>> + start_pfn = pfn;
>> + nr_contig = 1;
>> + } else if (start_pfn + nr_contig != pfn) {
>> + __free_contig_range(start_pfn, nr_contig);
>> + start_pfn = pfn;
>> + nr_contig = 1;
>> + cond_resched();
>> + } else {
>> + nr_contig++;
>> + }
>> + }
>
> Could we use num_pages_contiguous() here?
>
> while (nr_pages) {
> unsigned long nr_contig_pages = num_pages_contiguous(page_array, nr_pages);
>
> __free_contig_range(pfn_to_page(*page_array), nr_contig_pages);
>
> nr_pages -= nr_contig;
> page_array += nr_contig;
> cond_resched();
> }
>
> Something like that?
__free_contig_range() is already checking for the sections. If
num_pages_contiguous() is called here, it'll cause the duplication
of the section check.
>
>> + if (nr_contig)
>> + __free_contig_range(start_pfn, nr_contig);
>> +}
>> +
>> /*
>> * This is the 'heart' of the zoned buddy allocator.
>> */
>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>> index c607307c657a6..e9b3d6451e48b 100644
>> --- a/mm/vmalloc.c
>> +++ b/mm/vmalloc.c
>> @@ -3459,19 +3459,13 @@ void vfree(const void *addr)
>>
>> if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS))
>> vm_reset_perms(vm);
>> - for (i = 0; i < vm->nr_pages; i++) {
>> - struct page *page = vm->pages[i];
>>
>> - BUG_ON(!page);
>> - /*
>> - * High-order allocs for huge vmallocs are split, so
>> - * can be freed as an array of order-0 allocations
>> - */
>> - if (!(vm->flags & VM_MAP_PUT_PAGES))
>> - mod_lruvec_page_state(page, NR_VMALLOC, -1);
>> - __free_page(page);
>> - cond_resched();
>> + if (!(vm->flags & VM_MAP_PUT_PAGES)) {
>> + for (i = 0; i < vm->nr_pages; i++)
>> + mod_lruvec_page_state(vm->pages[i], NR_VMALLOC, -1);
>> }
>> + free_pages_bulk(vm->pages, vm->nr_pages);
>> +
>> kvfree(vm->pages);
>> kfree(vm);
>> }
>
>
On 3/25/26 15:26, Muhammad Usama Anjum wrote:
> On 25/03/2026 10:05 am, David Hildenbrand (Arm) wrote:
>> On 3/24/26 14:35, Muhammad Usama Anjum wrote:
>>> From: Ryan Roberts <ryan.roberts@arm.com>
>>>
>>> Whenever vmalloc allocates high order pages (e.g. for a huge mapping) it
>>> must immediately split_page() to order-0 so that it remains compatible
>>> with users that want to access the underlying struct page.
>>> Commit a06157804399 ("mm/vmalloc: request large order pages from buddy
>>> allocator") recently made it much more likely for vmalloc to allocate
>>> high order pages which are subsequently split to order-0.
>>>
>>> Unfortunately this had the side effect of causing performance
>>> regressions for tight vmalloc/vfree loops (e.g. test_vmalloc.ko
>>> benchmarks). See Closes: tag. This happens because the high order pages
>>> must be gotten from the buddy but then because they are split to
>>> order-0, when they are freed they are freed to the order-0 pcp.
>>> Previously allocation was for order-0 pages so they were recycled from
>>> the pcp.
>>>
>>> It would be preferable if when vmalloc allocates an (e.g.) order-3 page
>>> that it also frees that order-3 page to the order-3 pcp, then the
>>> regression could be removed.
>>>
>>> So let's do exactly that; use the new __free_contig_range() API to
>>> batch-free contiguous ranges of pfns. This not only removes the
>>> regression, but significantly improves performance of vfree beyond the
>>> baseline.
>>>
>>> A selection of test_vmalloc benchmarks running on arm64 server class
>>> system. mm-new is the baseline. Commit a06157804399 ("mm/vmalloc: request
>>> large order pages from buddy allocator") was added in v6.19-rc1 where we
>>> see regressions. Then with this change performance is much better. (>0
>>> is faster, <0 is slower, (R)/(I) = statistically significant
>>> Regression/Improvement):
>>>
>>> +-----------------+----------------------------------------------------------+-------------------+--------------------+
>>> | Benchmark | Result Class | mm-new | this series |
>>> +=================+==========================================================+===================+====================+
>>> | micromm/vmalloc | fix_align_alloc_test: p:1, h:0, l:500000 (usec) | 1331843.33 | (I) 67.17% |
>>> | | fix_size_alloc_test: p:1, h:0, l:500000 (usec) | 415907.33 | -5.14% |
>>> | | fix_size_alloc_test: p:4, h:0, l:500000 (usec) | 755448.00 | (I) 53.55% |
>>> | | fix_size_alloc_test: p:16, h:0, l:500000 (usec) | 1591331.33 | (I) 57.26% |
>>> | | fix_size_alloc_test: p:16, h:1, l:500000 (usec) | 1594345.67 | (I) 68.46% |
>>> | | fix_size_alloc_test: p:64, h:0, l:100000 (usec) | 1071826.00 | (I) 79.27% |
>>> | | fix_size_alloc_test: p:64, h:1, l:100000 (usec) | 1018385.00 | (I) 84.17% |
>>> | | fix_size_alloc_test: p:256, h:0, l:100000 (usec) | 3970899.67 | (I) 77.01% |
>>> | | fix_size_alloc_test: p:256, h:1, l:100000 (usec) | 3821788.67 | (I) 89.44% |
>>> | | fix_size_alloc_test: p:512, h:0, l:100000 (usec) | 7795968.00 | (I) 82.67% |
>>> | | fix_size_alloc_test: p:512, h:1, l:100000 (usec) | 6530169.67 | (I) 118.09% |
>>> | | full_fit_alloc_test: p:1, h:0, l:500000 (usec) | 626808.33 | -0.98% |
>>> | | kvfree_rcu_1_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 532145.67 | -1.68% |
>>> | | kvfree_rcu_2_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 537032.67 | -0.96% |
>>> | | long_busy_list_alloc_test: p:1, h:0, l:500000 (usec) | 8805069.00 | (I) 74.58% |
>>> | | pcpu_alloc_test: p:1, h:0, l:500000 (usec) | 500824.67 | 4.35% |
>>> | | random_size_align_alloc_test: p:1, h:0, l:500000 (usec) | 1637554.67 | (I) 76.99% |
>>> | | random_size_alloc_test: p:1, h:0, l:500000 (usec) | 4556288.67 | (I) 72.23% |
>>> | | vm_map_ram_test: p:1, h:0, l:500000 (usec) | 107371.00 | -0.70% |
>>> +-----------------+----------------------------------------------------------+-------------------+--------------------+
>>>
>>> Fixes: a06157804399 ("mm/vmalloc: request large order pages from buddy allocator")
>>> Closes: https://lore.kernel.org/all/66919a28-bc81-49c9-b68f-dd7c73395a0d@arm.com/
>>> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
>>> Co-developed-by: Muhammad Usama Anjum <usama.anjum@arm.com>
>>> Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>
>>> ---
>>> Changes since v2:
>>> - Remove BUG_ON in favour of simple implementation as this has never
>>> been seen to output any bug in the past as well
>>> - Move the free loop to separate function, free_pages_bulk()
>>> - Update stats, lruvec_stat in separate loop
>>>
>>> Changes since v1:
>>> - Rebase on mm-new
>>> - Rerun benchmarks
>>>
>>> Made-with: Cursor
>>> ---
>>> include/linux/gfp.h | 2 ++
>>> mm/page_alloc.c | 23 +++++++++++++++++++++++
>>> mm/vmalloc.c | 16 +++++-----------
>>> 3 files changed, 30 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
>>> index 7c1f9da7c8e56..71f9097ab99a0 100644
>>> --- a/include/linux/gfp.h
>>> +++ b/include/linux/gfp.h
>>> @@ -239,6 +239,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
>>> struct page **page_array);
>>> #define __alloc_pages_bulk(...) alloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))
>>>
>>> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages);
>>> +
>>> unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,
>>> unsigned long nr_pages,
>>> struct page **page_array);
>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>> index eedce9a30eb7e..250cc07e547b8 100644
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -5175,6 +5175,29 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
>>> }
>>> EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);
>>>
>>
>> Can we add some kerneldoc describing call context etc?
> Yes, I'll add short kerneldoc here.
>>
>>> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages)
>>> +{
>>> + unsigned long start_pfn = 0, pfn;
>>> + unsigned long i, nr_contig = 0;
>>> +
>>> + for (i = 0; i < nr_pages; i++) {
>>> + pfn = page_to_pfn(page_array[i]);
>>> + if (!nr_contig) {
>>> + start_pfn = pfn;
>>> + nr_contig = 1;
>>> + } else if (start_pfn + nr_contig != pfn) {
>>> + __free_contig_range(start_pfn, nr_contig);
>>> + start_pfn = pfn;
>>> + nr_contig = 1;
>>> + cond_resched();
>>> + } else {
>>> + nr_contig++;
>>> + }
>>> + }
>>
>> Could we use num_pages_contiguous() here?
>>
>> while (nr_pages) {
>> unsigned long nr_contig_pages = num_pages_contiguous(page_array, nr_pages);
>>
>> __free_contig_range(pfn_to_page(*page_array), nr_contig_pages);
>>
>> nr_pages -= nr_contig;
>> page_array += nr_contig;
>> cond_resched();
>> }
>>
>> Something like that?
> __free_contig_range() is already checking for the sections. If
> num_pages_contiguous() is called here, it'll cause the duplication
> of the section check.
No problem. For configs we care about it's optimized out entirely either
way.
--
Cheers,
David
On 24 Mar 2026, at 9:35, Muhammad Usama Anjum wrote:
> From: Ryan Roberts <ryan.roberts@arm.com>
>
> Whenever vmalloc allocates high order pages (e.g. for a huge mapping) it
> must immediately split_page() to order-0 so that it remains compatible
> with users that want to access the underlying struct page.
> Commit a06157804399 ("mm/vmalloc: request large order pages from buddy
> allocator") recently made it much more likely for vmalloc to allocate
> high order pages which are subsequently split to order-0.
>
> Unfortunately this had the side effect of causing performance
> regressions for tight vmalloc/vfree loops (e.g. test_vmalloc.ko
> benchmarks). See Closes: tag. This happens because the high order pages
> must be gotten from the buddy but then because they are split to
> order-0, when they are freed they are freed to the order-0 pcp.
> Previously allocation was for order-0 pages so they were recycled from
> the pcp.
>
> It would be preferable if when vmalloc allocates an (e.g.) order-3 page
> that it also frees that order-3 page to the order-3 pcp, then the
> regression could be removed.
>
> So let's do exactly that; use the new __free_contig_range() API to
> batch-free contiguous ranges of pfns. This not only removes the
> regression, but significantly improves performance of vfree beyond the
> baseline.
>
> A selection of test_vmalloc benchmarks running on arm64 server class
> system. mm-new is the baseline. Commit a06157804399 ("mm/vmalloc: request
> large order pages from buddy allocator") was added in v6.19-rc1 where we
> see regressions. Then with this change performance is much better. (>0
> is faster, <0 is slower, (R)/(I) = statistically significant
> Regression/Improvement):
>
> +-----------------+----------------------------------------------------------+-------------------+--------------------+
> | Benchmark | Result Class | mm-new | this series |
> +=================+==========================================================+===================+====================+
> | micromm/vmalloc | fix_align_alloc_test: p:1, h:0, l:500000 (usec) | 1331843.33 | (I) 67.17% |
> | | fix_size_alloc_test: p:1, h:0, l:500000 (usec) | 415907.33 | -5.14% |
> | | fix_size_alloc_test: p:4, h:0, l:500000 (usec) | 755448.00 | (I) 53.55% |
> | | fix_size_alloc_test: p:16, h:0, l:500000 (usec) | 1591331.33 | (I) 57.26% |
> | | fix_size_alloc_test: p:16, h:1, l:500000 (usec) | 1594345.67 | (I) 68.46% |
> | | fix_size_alloc_test: p:64, h:0, l:100000 (usec) | 1071826.00 | (I) 79.27% |
> | | fix_size_alloc_test: p:64, h:1, l:100000 (usec) | 1018385.00 | (I) 84.17% |
> | | fix_size_alloc_test: p:256, h:0, l:100000 (usec) | 3970899.67 | (I) 77.01% |
> | | fix_size_alloc_test: p:256, h:1, l:100000 (usec) | 3821788.67 | (I) 89.44% |
> | | fix_size_alloc_test: p:512, h:0, l:100000 (usec) | 7795968.00 | (I) 82.67% |
> | | fix_size_alloc_test: p:512, h:1, l:100000 (usec) | 6530169.67 | (I) 118.09% |
> | | full_fit_alloc_test: p:1, h:0, l:500000 (usec) | 626808.33 | -0.98% |
> | | kvfree_rcu_1_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 532145.67 | -1.68% |
> | | kvfree_rcu_2_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 537032.67 | -0.96% |
> | | long_busy_list_alloc_test: p:1, h:0, l:500000 (usec) | 8805069.00 | (I) 74.58% |
> | | pcpu_alloc_test: p:1, h:0, l:500000 (usec) | 500824.67 | 4.35% |
> | | random_size_align_alloc_test: p:1, h:0, l:500000 (usec) | 1637554.67 | (I) 76.99% |
> | | random_size_alloc_test: p:1, h:0, l:500000 (usec) | 4556288.67 | (I) 72.23% |
> | | vm_map_ram_test: p:1, h:0, l:500000 (usec) | 107371.00 | -0.70% |
> +-----------------+----------------------------------------------------------+-------------------+--------------------+
>
> Fixes: a06157804399 ("mm/vmalloc: request large order pages from buddy allocator")
> Closes: https://lore.kernel.org/all/66919a28-bc81-49c9-b68f-dd7c73395a0d@arm.com/
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> Co-developed-by: Muhammad Usama Anjum <usama.anjum@arm.com>
> Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>
> ---
> Changes since v2:
> - Remove BUG_ON in favour of simple implementation as this has never
> been seen to output any bug in the past as well
> - Move the free loop to separate function, free_pages_bulk()
> - Update stats, lruvec_stat in separate loop
>
> Changes since v1:
> - Rebase on mm-new
> - Rerun benchmarks
>
> Made-with: Cursor
> ---
> include/linux/gfp.h | 2 ++
> mm/page_alloc.c | 23 +++++++++++++++++++++++
> mm/vmalloc.c | 16 +++++-----------
> 3 files changed, 30 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 7c1f9da7c8e56..71f9097ab99a0 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -239,6 +239,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
> struct page **page_array);
> #define __alloc_pages_bulk(...) alloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))
>
> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages);
> +
> unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,
> unsigned long nr_pages,
> struct page **page_array);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index eedce9a30eb7e..250cc07e547b8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5175,6 +5175,29 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
> }
> EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);
>
> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages)
> +{
> + unsigned long start_pfn = 0, pfn;
> + unsigned long i, nr_contig = 0;
> +
> + for (i = 0; i < nr_pages; i++) {
> + pfn = page_to_pfn(page_array[i]);
> + if (!nr_contig) {
> + start_pfn = pfn;
> + nr_contig = 1;
> + } else if (start_pfn + nr_contig != pfn) {
> + __free_contig_range(start_pfn, nr_contig);
> + start_pfn = pfn;
> + nr_contig = 1;
> + cond_resched();
> + } else {
> + nr_contig++;
> + }
> + }
> + if (nr_contig)
> + __free_contig_range(start_pfn, nr_contig);
> +}
free_pages_bulk() assumes pages in page_array are sorted in PFN ascending order.
I think it is worth documenting it, since without sorting, it can degrade
back to the original implementation.
> +
> /*
> * This is the 'heart' of the zoned buddy allocator.
> */
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index c607307c657a6..e9b3d6451e48b 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3459,19 +3459,13 @@ void vfree(const void *addr)
>
> if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS))
> vm_reset_perms(vm);
> - for (i = 0; i < vm->nr_pages; i++) {
> - struct page *page = vm->pages[i];
>
> - BUG_ON(!page);
> - /*
> - * High-order allocs for huge vmallocs are split, so
> - * can be freed as an array of order-0 allocations
> - */
> - if (!(vm->flags & VM_MAP_PUT_PAGES))
> - mod_lruvec_page_state(page, NR_VMALLOC, -1);
> - __free_page(page);
> - cond_resched();
> + if (!(vm->flags & VM_MAP_PUT_PAGES)) {
> + for (i = 0; i < vm->nr_pages; i++)
> + mod_lruvec_page_state(vm->pages[i], NR_VMALLOC, -1);
> }
> + free_pages_bulk(vm->pages, vm->nr_pages);
> +
stats is updated before any page is freed. It is better to mention
it in the commit message.
> kvfree(vm->pages);
> kfree(vm);
> }
> --
> 2.47.3
Otherwise, LGTM.
Acked-by: Zi Yan <ziy@nvidia.com>
Best Regards,
Yan, Zi
<snip>
>> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages)
>> +{
>> + unsigned long start_pfn = 0, pfn;
>> + unsigned long i, nr_contig = 0;
>> +
>> + for (i = 0; i < nr_pages; i++) {
>> + pfn = page_to_pfn(page_array[i]);
>> + if (!nr_contig) {
>> + start_pfn = pfn;
>> + nr_contig = 1;
>> + } else if (start_pfn + nr_contig != pfn) {
>> + __free_contig_range(start_pfn, nr_contig);
>> + start_pfn = pfn;
>> + nr_contig = 1;
>> + cond_resched();
>> + } else {
>> + nr_contig++;
>> + }
>> + }
>> + if (nr_contig)
>> + __free_contig_range(start_pfn, nr_contig);
>> +}
>
> free_pages_bulk() assumes pages in page_array are sorted in PFN ascending order.
> I think it is worth documenting it, since without sorting, it can degrade
> back to the original implementation.
I'll add the kerneldoc comment.
>
>> +
>> /*
>> * This is the 'heart' of the zoned buddy allocator.
>> */
>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>> index c607307c657a6..e9b3d6451e48b 100644
>> --- a/mm/vmalloc.c
>> +++ b/mm/vmalloc.c
>> @@ -3459,19 +3459,13 @@ void vfree(const void *addr)
>>
>> if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS))
>> vm_reset_perms(vm);
>> - for (i = 0; i < vm->nr_pages; i++) {
>> - struct page *page = vm->pages[i];
>>
>> - BUG_ON(!page);
>> - /*
>> - * High-order allocs for huge vmallocs are split, so
>> - * can be freed as an array of order-0 allocations
>> - */
>> - if (!(vm->flags & VM_MAP_PUT_PAGES))
>> - mod_lruvec_page_state(page, NR_VMALLOC, -1);
>> - __free_page(page);
>> - cond_resched();
>> + if (!(vm->flags & VM_MAP_PUT_PAGES)) {
>> + for (i = 0; i < vm->nr_pages; i++)
>> + mod_lruvec_page_state(vm->pages[i], NR_VMALLOC, -1);
>> }
>> + free_pages_bulk(vm->pages, vm->nr_pages);
>> +
>
> stats is updated before any page is freed. It is better to mention
> it in the commit message.
I'll mention it.
>
>> kvfree(vm->pages);
>> kfree(vm);
>> }
>> --
>> 2.47.3
>
> Otherwise, LGTM.
>
> Acked-by: Zi Yan <ziy@nvidia.com>
>
> Best Regards,
> Yan, Zi
>
Thanks,
Usama
On Tue, Mar 24, 2026 at 10:55:55AM -0400, Zi Yan wrote:
> On 24 Mar 2026, at 9:35, Muhammad Usama Anjum wrote:
>
> > From: Ryan Roberts <ryan.roberts@arm.com>
> >
> > Whenever vmalloc allocates high order pages (e.g. for a huge mapping) it
> > must immediately split_page() to order-0 so that it remains compatible
> > with users that want to access the underlying struct page.
> > Commit a06157804399 ("mm/vmalloc: request large order pages from buddy
> > allocator") recently made it much more likely for vmalloc to allocate
> > high order pages which are subsequently split to order-0.
> >
> > Unfortunately this had the side effect of causing performance
> > regressions for tight vmalloc/vfree loops (e.g. test_vmalloc.ko
> > benchmarks). See Closes: tag. This happens because the high order pages
> > must be gotten from the buddy but then because they are split to
> > order-0, when they are freed they are freed to the order-0 pcp.
> > Previously allocation was for order-0 pages so they were recycled from
> > the pcp.
> >
> > It would be preferable if when vmalloc allocates an (e.g.) order-3 page
> > that it also frees that order-3 page to the order-3 pcp, then the
> > regression could be removed.
> >
> > So let's do exactly that; use the new __free_contig_range() API to
> > batch-free contiguous ranges of pfns. This not only removes the
> > regression, but significantly improves performance of vfree beyond the
> > baseline.
> >
> > A selection of test_vmalloc benchmarks running on arm64 server class
> > system. mm-new is the baseline. Commit a06157804399 ("mm/vmalloc: request
> > large order pages from buddy allocator") was added in v6.19-rc1 where we
> > see regressions. Then with this change performance is much better. (>0
> > is faster, <0 is slower, (R)/(I) = statistically significant
> > Regression/Improvement):
> >
> > +-----------------+----------------------------------------------------------+-------------------+--------------------+
> > | Benchmark | Result Class | mm-new | this series |
> > +=================+==========================================================+===================+====================+
> > | micromm/vmalloc | fix_align_alloc_test: p:1, h:0, l:500000 (usec) | 1331843.33 | (I) 67.17% |
> > | | fix_size_alloc_test: p:1, h:0, l:500000 (usec) | 415907.33 | -5.14% |
> > | | fix_size_alloc_test: p:4, h:0, l:500000 (usec) | 755448.00 | (I) 53.55% |
> > | | fix_size_alloc_test: p:16, h:0, l:500000 (usec) | 1591331.33 | (I) 57.26% |
> > | | fix_size_alloc_test: p:16, h:1, l:500000 (usec) | 1594345.67 | (I) 68.46% |
> > | | fix_size_alloc_test: p:64, h:0, l:100000 (usec) | 1071826.00 | (I) 79.27% |
> > | | fix_size_alloc_test: p:64, h:1, l:100000 (usec) | 1018385.00 | (I) 84.17% |
> > | | fix_size_alloc_test: p:256, h:0, l:100000 (usec) | 3970899.67 | (I) 77.01% |
> > | | fix_size_alloc_test: p:256, h:1, l:100000 (usec) | 3821788.67 | (I) 89.44% |
> > | | fix_size_alloc_test: p:512, h:0, l:100000 (usec) | 7795968.00 | (I) 82.67% |
> > | | fix_size_alloc_test: p:512, h:1, l:100000 (usec) | 6530169.67 | (I) 118.09% |
> > | | full_fit_alloc_test: p:1, h:0, l:500000 (usec) | 626808.33 | -0.98% |
> > | | kvfree_rcu_1_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 532145.67 | -1.68% |
> > | | kvfree_rcu_2_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 537032.67 | -0.96% |
> > | | long_busy_list_alloc_test: p:1, h:0, l:500000 (usec) | 8805069.00 | (I) 74.58% |
> > | | pcpu_alloc_test: p:1, h:0, l:500000 (usec) | 500824.67 | 4.35% |
> > | | random_size_align_alloc_test: p:1, h:0, l:500000 (usec) | 1637554.67 | (I) 76.99% |
> > | | random_size_alloc_test: p:1, h:0, l:500000 (usec) | 4556288.67 | (I) 72.23% |
> > | | vm_map_ram_test: p:1, h:0, l:500000 (usec) | 107371.00 | -0.70% |
> > +-----------------+----------------------------------------------------------+-------------------+--------------------+
> >
> > Fixes: a06157804399 ("mm/vmalloc: request large order pages from buddy allocator")
> > Closes: https://lore.kernel.org/all/66919a28-bc81-49c9-b68f-dd7c73395a0d@arm.com/
> > Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> > Co-developed-by: Muhammad Usama Anjum <usama.anjum@arm.com>
> > Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>
> > ---
> > Changes since v2:
> > - Remove BUG_ON in favour of simple implementation as this has never
> > been seen to output any bug in the past as well
> > - Move the free loop to separate function, free_pages_bulk()
> > - Update stats, lruvec_stat in separate loop
> >
> > Changes since v1:
> > - Rebase on mm-new
> > - Rerun benchmarks
> >
> > Made-with: Cursor
> > ---
> > include/linux/gfp.h | 2 ++
> > mm/page_alloc.c | 23 +++++++++++++++++++++++
> > mm/vmalloc.c | 16 +++++-----------
> > 3 files changed, 30 insertions(+), 11 deletions(-)
> >
> > diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> > index 7c1f9da7c8e56..71f9097ab99a0 100644
> > --- a/include/linux/gfp.h
> > +++ b/include/linux/gfp.h
> > @@ -239,6 +239,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
> > struct page **page_array);
> > #define __alloc_pages_bulk(...) alloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))
> >
> > +void free_pages_bulk(struct page **page_array, unsigned long nr_pages);
> > +
> > unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,
> > unsigned long nr_pages,
> > struct page **page_array);
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index eedce9a30eb7e..250cc07e547b8 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -5175,6 +5175,29 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
> > }
> > EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);
> >
> > +void free_pages_bulk(struct page **page_array, unsigned long nr_pages)
> > +{
> > + unsigned long start_pfn = 0, pfn;
> > + unsigned long i, nr_contig = 0;
> > +
> > + for (i = 0; i < nr_pages; i++) {
> > + pfn = page_to_pfn(page_array[i]);
> > + if (!nr_contig) {
> > + start_pfn = pfn;
> > + nr_contig = 1;
> > + } else if (start_pfn + nr_contig != pfn) {
> > + __free_contig_range(start_pfn, nr_contig);
> > + start_pfn = pfn;
> > + nr_contig = 1;
> > + cond_resched();
>
It will cause schedule while atomic. Have you checked that
__free_contig_range() also can sleep? Of so then we are aligned, if not
probably we should remove it.
--
Uladzislau Rezki
On 25/03/2026 8:56 am, Uladzislau Rezki wrote:
> On Tue, Mar 24, 2026 at 10:55:55AM -0400, Zi Yan wrote:
>> On 24 Mar 2026, at 9:35, Muhammad Usama Anjum wrote:
>>
>>> From: Ryan Roberts <ryan.roberts@arm.com>
>>>
>>> Whenever vmalloc allocates high order pages (e.g. for a huge mapping) it
>>> must immediately split_page() to order-0 so that it remains compatible
>>> with users that want to access the underlying struct page.
>>> Commit a06157804399 ("mm/vmalloc: request large order pages from buddy
>>> allocator") recently made it much more likely for vmalloc to allocate
>>> high order pages which are subsequently split to order-0.
>>>
>>> Unfortunately this had the side effect of causing performance
>>> regressions for tight vmalloc/vfree loops (e.g. test_vmalloc.ko
>>> benchmarks). See Closes: tag. This happens because the high order pages
>>> must be gotten from the buddy but then because they are split to
>>> order-0, when they are freed they are freed to the order-0 pcp.
>>> Previously allocation was for order-0 pages so they were recycled from
>>> the pcp.
>>>
>>> It would be preferable if when vmalloc allocates an (e.g.) order-3 page
>>> that it also frees that order-3 page to the order-3 pcp, then the
>>> regression could be removed.
>>>
>>> So let's do exactly that; use the new __free_contig_range() API to
>>> batch-free contiguous ranges of pfns. This not only removes the
>>> regression, but significantly improves performance of vfree beyond the
>>> baseline.
>>>
>>> A selection of test_vmalloc benchmarks running on arm64 server class
>>> system. mm-new is the baseline. Commit a06157804399 ("mm/vmalloc: request
>>> large order pages from buddy allocator") was added in v6.19-rc1 where we
>>> see regressions. Then with this change performance is much better. (>0
>>> is faster, <0 is slower, (R)/(I) = statistically significant
>>> Regression/Improvement):
>>>
>>> +-----------------+----------------------------------------------------------+-------------------+--------------------+
>>> | Benchmark | Result Class | mm-new | this series |
>>> +=================+==========================================================+===================+====================+
>>> | micromm/vmalloc | fix_align_alloc_test: p:1, h:0, l:500000 (usec) | 1331843.33 | (I) 67.17% |
>>> | | fix_size_alloc_test: p:1, h:0, l:500000 (usec) | 415907.33 | -5.14% |
>>> | | fix_size_alloc_test: p:4, h:0, l:500000 (usec) | 755448.00 | (I) 53.55% |
>>> | | fix_size_alloc_test: p:16, h:0, l:500000 (usec) | 1591331.33 | (I) 57.26% |
>>> | | fix_size_alloc_test: p:16, h:1, l:500000 (usec) | 1594345.67 | (I) 68.46% |
>>> | | fix_size_alloc_test: p:64, h:0, l:100000 (usec) | 1071826.00 | (I) 79.27% |
>>> | | fix_size_alloc_test: p:64, h:1, l:100000 (usec) | 1018385.00 | (I) 84.17% |
>>> | | fix_size_alloc_test: p:256, h:0, l:100000 (usec) | 3970899.67 | (I) 77.01% |
>>> | | fix_size_alloc_test: p:256, h:1, l:100000 (usec) | 3821788.67 | (I) 89.44% |
>>> | | fix_size_alloc_test: p:512, h:0, l:100000 (usec) | 7795968.00 | (I) 82.67% |
>>> | | fix_size_alloc_test: p:512, h:1, l:100000 (usec) | 6530169.67 | (I) 118.09% |
>>> | | full_fit_alloc_test: p:1, h:0, l:500000 (usec) | 626808.33 | -0.98% |
>>> | | kvfree_rcu_1_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 532145.67 | -1.68% |
>>> | | kvfree_rcu_2_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 537032.67 | -0.96% |
>>> | | long_busy_list_alloc_test: p:1, h:0, l:500000 (usec) | 8805069.00 | (I) 74.58% |
>>> | | pcpu_alloc_test: p:1, h:0, l:500000 (usec) | 500824.67 | 4.35% |
>>> | | random_size_align_alloc_test: p:1, h:0, l:500000 (usec) | 1637554.67 | (I) 76.99% |
>>> | | random_size_alloc_test: p:1, h:0, l:500000 (usec) | 4556288.67 | (I) 72.23% |
>>> | | vm_map_ram_test: p:1, h:0, l:500000 (usec) | 107371.00 | -0.70% |
>>> +-----------------+----------------------------------------------------------+-------------------+--------------------+
>>>
>>> Fixes: a06157804399 ("mm/vmalloc: request large order pages from buddy allocator")
>>> Closes: https://lore.kernel.org/all/66919a28-bc81-49c9-b68f-dd7c73395a0d@arm.com/
>>> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
>>> Co-developed-by: Muhammad Usama Anjum <usama.anjum@arm.com>
>>> Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>
>>> ---
>>> Changes since v2:
>>> - Remove BUG_ON in favour of simple implementation as this has never
>>> been seen to output any bug in the past as well
>>> - Move the free loop to separate function, free_pages_bulk()
>>> - Update stats, lruvec_stat in separate loop
>>>
>>> Changes since v1:
>>> - Rebase on mm-new
>>> - Rerun benchmarks
>>>
>>> Made-with: Cursor
>>> ---
>>> include/linux/gfp.h | 2 ++
>>> mm/page_alloc.c | 23 +++++++++++++++++++++++
>>> mm/vmalloc.c | 16 +++++-----------
>>> 3 files changed, 30 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
>>> index 7c1f9da7c8e56..71f9097ab99a0 100644
>>> --- a/include/linux/gfp.h
>>> +++ b/include/linux/gfp.h
>>> @@ -239,6 +239,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
>>> struct page **page_array);
>>> #define __alloc_pages_bulk(...) alloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))
>>>
>>> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages);
>>> +
>>> unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,
>>> unsigned long nr_pages,
>>> struct page **page_array);
>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>> index eedce9a30eb7e..250cc07e547b8 100644
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -5175,6 +5175,29 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
>>> }
>>> EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);
>>>
>>> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages)
>>> +{
>>> + unsigned long start_pfn = 0, pfn;
>>> + unsigned long i, nr_contig = 0;
>>> +
>>> + for (i = 0; i < nr_pages; i++) {
>>> + pfn = page_to_pfn(page_array[i]);
>>> + if (!nr_contig) {
>>> + start_pfn = pfn;
>>> + nr_contig = 1;
>>> + } else if (start_pfn + nr_contig != pfn) {
>>> + __free_contig_range(start_pfn, nr_contig);
>>> + start_pfn = pfn;
>>> + nr_contig = 1;
>>> + cond_resched();
>>
> It will cause schedule while atomic. Have you checked that
> __free_contig_range() also can sleep? Of so then we are aligned, if not
> probably we should remove it.
Sorry, I didn't get it. How does having cond_resched() in this function
affects __free_contig_range()?
The current user of this function is only vfree() which is sleepable.
Thanks,
Usama
>
> --
> Uladzislau Rezki
>
On Wed, Mar 25, 2026 at 03:02:14PM +0000, Muhammad Usama Anjum wrote:
> On 25/03/2026 8:56 am, Uladzislau Rezki wrote:
> > On Tue, Mar 24, 2026 at 10:55:55AM -0400, Zi Yan wrote:
> >> On 24 Mar 2026, at 9:35, Muhammad Usama Anjum wrote:
> >>
> >>> From: Ryan Roberts <ryan.roberts@arm.com>
> >>>
> >>> Whenever vmalloc allocates high order pages (e.g. for a huge mapping) it
> >>> must immediately split_page() to order-0 so that it remains compatible
> >>> with users that want to access the underlying struct page.
> >>> Commit a06157804399 ("mm/vmalloc: request large order pages from buddy
> >>> allocator") recently made it much more likely for vmalloc to allocate
> >>> high order pages which are subsequently split to order-0.
> >>>
> >>> Unfortunately this had the side effect of causing performance
> >>> regressions for tight vmalloc/vfree loops (e.g. test_vmalloc.ko
> >>> benchmarks). See Closes: tag. This happens because the high order pages
> >>> must be gotten from the buddy but then because they are split to
> >>> order-0, when they are freed they are freed to the order-0 pcp.
> >>> Previously allocation was for order-0 pages so they were recycled from
> >>> the pcp.
> >>>
> >>> It would be preferable if when vmalloc allocates an (e.g.) order-3 page
> >>> that it also frees that order-3 page to the order-3 pcp, then the
> >>> regression could be removed.
> >>>
> >>> So let's do exactly that; use the new __free_contig_range() API to
> >>> batch-free contiguous ranges of pfns. This not only removes the
> >>> regression, but significantly improves performance of vfree beyond the
> >>> baseline.
> >>>
> >>> A selection of test_vmalloc benchmarks running on arm64 server class
> >>> system. mm-new is the baseline. Commit a06157804399 ("mm/vmalloc: request
> >>> large order pages from buddy allocator") was added in v6.19-rc1 where we
> >>> see regressions. Then with this change performance is much better. (>0
> >>> is faster, <0 is slower, (R)/(I) = statistically significant
> >>> Regression/Improvement):
> >>>
> >>> +-----------------+----------------------------------------------------------+-------------------+--------------------+
> >>> | Benchmark | Result Class | mm-new | this series |
> >>> +=================+==========================================================+===================+====================+
> >>> | micromm/vmalloc | fix_align_alloc_test: p:1, h:0, l:500000 (usec) | 1331843.33 | (I) 67.17% |
> >>> | | fix_size_alloc_test: p:1, h:0, l:500000 (usec) | 415907.33 | -5.14% |
> >>> | | fix_size_alloc_test: p:4, h:0, l:500000 (usec) | 755448.00 | (I) 53.55% |
> >>> | | fix_size_alloc_test: p:16, h:0, l:500000 (usec) | 1591331.33 | (I) 57.26% |
> >>> | | fix_size_alloc_test: p:16, h:1, l:500000 (usec) | 1594345.67 | (I) 68.46% |
> >>> | | fix_size_alloc_test: p:64, h:0, l:100000 (usec) | 1071826.00 | (I) 79.27% |
> >>> | | fix_size_alloc_test: p:64, h:1, l:100000 (usec) | 1018385.00 | (I) 84.17% |
> >>> | | fix_size_alloc_test: p:256, h:0, l:100000 (usec) | 3970899.67 | (I) 77.01% |
> >>> | | fix_size_alloc_test: p:256, h:1, l:100000 (usec) | 3821788.67 | (I) 89.44% |
> >>> | | fix_size_alloc_test: p:512, h:0, l:100000 (usec) | 7795968.00 | (I) 82.67% |
> >>> | | fix_size_alloc_test: p:512, h:1, l:100000 (usec) | 6530169.67 | (I) 118.09% |
> >>> | | full_fit_alloc_test: p:1, h:0, l:500000 (usec) | 626808.33 | -0.98% |
> >>> | | kvfree_rcu_1_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 532145.67 | -1.68% |
> >>> | | kvfree_rcu_2_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 537032.67 | -0.96% |
> >>> | | long_busy_list_alloc_test: p:1, h:0, l:500000 (usec) | 8805069.00 | (I) 74.58% |
> >>> | | pcpu_alloc_test: p:1, h:0, l:500000 (usec) | 500824.67 | 4.35% |
> >>> | | random_size_align_alloc_test: p:1, h:0, l:500000 (usec) | 1637554.67 | (I) 76.99% |
> >>> | | random_size_alloc_test: p:1, h:0, l:500000 (usec) | 4556288.67 | (I) 72.23% |
> >>> | | vm_map_ram_test: p:1, h:0, l:500000 (usec) | 107371.00 | -0.70% |
> >>> +-----------------+----------------------------------------------------------+-------------------+--------------------+
> >>>
> >>> Fixes: a06157804399 ("mm/vmalloc: request large order pages from buddy allocator")
> >>> Closes: https://lore.kernel.org/all/66919a28-bc81-49c9-b68f-dd7c73395a0d@arm.com/
> >>> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> >>> Co-developed-by: Muhammad Usama Anjum <usama.anjum@arm.com>
> >>> Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>
> >>> ---
> >>> Changes since v2:
> >>> - Remove BUG_ON in favour of simple implementation as this has never
> >>> been seen to output any bug in the past as well
> >>> - Move the free loop to separate function, free_pages_bulk()
> >>> - Update stats, lruvec_stat in separate loop
> >>>
> >>> Changes since v1:
> >>> - Rebase on mm-new
> >>> - Rerun benchmarks
> >>>
> >>> Made-with: Cursor
> >>> ---
> >>> include/linux/gfp.h | 2 ++
> >>> mm/page_alloc.c | 23 +++++++++++++++++++++++
> >>> mm/vmalloc.c | 16 +++++-----------
> >>> 3 files changed, 30 insertions(+), 11 deletions(-)
> >>>
> >>> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> >>> index 7c1f9da7c8e56..71f9097ab99a0 100644
> >>> --- a/include/linux/gfp.h
> >>> +++ b/include/linux/gfp.h
> >>> @@ -239,6 +239,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
> >>> struct page **page_array);
> >>> #define __alloc_pages_bulk(...) alloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))
> >>>
> >>> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages);
> >>> +
> >>> unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,
> >>> unsigned long nr_pages,
> >>> struct page **page_array);
> >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> >>> index eedce9a30eb7e..250cc07e547b8 100644
> >>> --- a/mm/page_alloc.c
> >>> +++ b/mm/page_alloc.c
> >>> @@ -5175,6 +5175,29 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
> >>> }
> >>> EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);
> >>>
> >>> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages)
> >>> +{
> >>> + unsigned long start_pfn = 0, pfn;
> >>> + unsigned long i, nr_contig = 0;
> >>> +
> >>> + for (i = 0; i < nr_pages; i++) {
> >>> + pfn = page_to_pfn(page_array[i]);
> >>> + if (!nr_contig) {
> >>> + start_pfn = pfn;
> >>> + nr_contig = 1;
> >>> + } else if (start_pfn + nr_contig != pfn) {
> >>> + __free_contig_range(start_pfn, nr_contig);
> >>> + start_pfn = pfn;
> >>> + nr_contig = 1;
> >>> + cond_resched();
> >>
> > It will cause schedule while atomic. Have you checked that
> > __free_contig_range() also can sleep? Of so then we are aligned, if not
> > probably we should remove it.
> Sorry, I didn't get it. How does having cond_resched() in this function
> affects __free_contig_range()?
>
It is not. What i am asking is about:
<snip>
spin_lock();
free_pages_bulk()
...
<snip>
so this is not allowed because there is cond_resched() call. We
can remove it and make it possible to invoke free_pages_bulk() under
spin-lock, __but__ only if for example other calls do not sleep:
__free_contig_range()
memdesc_section()
free_prepared_contig_range()
...
>
> The current user of this function is only vfree() which is sleepable.
>
I know. But this function can be used by others soon or later.
Another option is add a comment, saying that it is only for sleepable
contexts.
--
Uladzislau Rezki
On 25/03/2026 4:16 pm, Uladzislau Rezki wrote:
> On Wed, Mar 25, 2026 at 03:02:14PM +0000, Muhammad Usama Anjum wrote:
>> On 25/03/2026 8:56 am, Uladzislau Rezki wrote:
>>> On Tue, Mar 24, 2026 at 10:55:55AM -0400, Zi Yan wrote:
>>>> On 24 Mar 2026, at 9:35, Muhammad Usama Anjum wrote:
>>>>
>>>>> From: Ryan Roberts <ryan.roberts@arm.com>
>>>>>
>>>>> Whenever vmalloc allocates high order pages (e.g. for a huge mapping) it
>>>>> must immediately split_page() to order-0 so that it remains compatible
>>>>> with users that want to access the underlying struct page.
>>>>> Commit a06157804399 ("mm/vmalloc: request large order pages from buddy
>>>>> allocator") recently made it much more likely for vmalloc to allocate
>>>>> high order pages which are subsequently split to order-0.
>>>>>
>>>>> Unfortunately this had the side effect of causing performance
>>>>> regressions for tight vmalloc/vfree loops (e.g. test_vmalloc.ko
>>>>> benchmarks). See Closes: tag. This happens because the high order pages
>>>>> must be gotten from the buddy but then because they are split to
>>>>> order-0, when they are freed they are freed to the order-0 pcp.
>>>>> Previously allocation was for order-0 pages so they were recycled from
>>>>> the pcp.
>>>>>
>>>>> It would be preferable if when vmalloc allocates an (e.g.) order-3 page
>>>>> that it also frees that order-3 page to the order-3 pcp, then the
>>>>> regression could be removed.
>>>>>
>>>>> So let's do exactly that; use the new __free_contig_range() API to
>>>>> batch-free contiguous ranges of pfns. This not only removes the
>>>>> regression, but significantly improves performance of vfree beyond the
>>>>> baseline.
>>>>>
>>>>> A selection of test_vmalloc benchmarks running on arm64 server class
>>>>> system. mm-new is the baseline. Commit a06157804399 ("mm/vmalloc: request
>>>>> large order pages from buddy allocator") was added in v6.19-rc1 where we
>>>>> see regressions. Then with this change performance is much better. (>0
>>>>> is faster, <0 is slower, (R)/(I) = statistically significant
>>>>> Regression/Improvement):
>>>>>
>>>>> +-----------------+----------------------------------------------------------+-------------------+--------------------+
>>>>> | Benchmark | Result Class | mm-new | this series |
>>>>> +=================+==========================================================+===================+====================+
>>>>> | micromm/vmalloc | fix_align_alloc_test: p:1, h:0, l:500000 (usec) | 1331843.33 | (I) 67.17% |
>>>>> | | fix_size_alloc_test: p:1, h:0, l:500000 (usec) | 415907.33 | -5.14% |
>>>>> | | fix_size_alloc_test: p:4, h:0, l:500000 (usec) | 755448.00 | (I) 53.55% |
>>>>> | | fix_size_alloc_test: p:16, h:0, l:500000 (usec) | 1591331.33 | (I) 57.26% |
>>>>> | | fix_size_alloc_test: p:16, h:1, l:500000 (usec) | 1594345.67 | (I) 68.46% |
>>>>> | | fix_size_alloc_test: p:64, h:0, l:100000 (usec) | 1071826.00 | (I) 79.27% |
>>>>> | | fix_size_alloc_test: p:64, h:1, l:100000 (usec) | 1018385.00 | (I) 84.17% |
>>>>> | | fix_size_alloc_test: p:256, h:0, l:100000 (usec) | 3970899.67 | (I) 77.01% |
>>>>> | | fix_size_alloc_test: p:256, h:1, l:100000 (usec) | 3821788.67 | (I) 89.44% |
>>>>> | | fix_size_alloc_test: p:512, h:0, l:100000 (usec) | 7795968.00 | (I) 82.67% |
>>>>> | | fix_size_alloc_test: p:512, h:1, l:100000 (usec) | 6530169.67 | (I) 118.09% |
>>>>> | | full_fit_alloc_test: p:1, h:0, l:500000 (usec) | 626808.33 | -0.98% |
>>>>> | | kvfree_rcu_1_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 532145.67 | -1.68% |
>>>>> | | kvfree_rcu_2_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 537032.67 | -0.96% |
>>>>> | | long_busy_list_alloc_test: p:1, h:0, l:500000 (usec) | 8805069.00 | (I) 74.58% |
>>>>> | | pcpu_alloc_test: p:1, h:0, l:500000 (usec) | 500824.67 | 4.35% |
>>>>> | | random_size_align_alloc_test: p:1, h:0, l:500000 (usec) | 1637554.67 | (I) 76.99% |
>>>>> | | random_size_alloc_test: p:1, h:0, l:500000 (usec) | 4556288.67 | (I) 72.23% |
>>>>> | | vm_map_ram_test: p:1, h:0, l:500000 (usec) | 107371.00 | -0.70% |
>>>>> +-----------------+----------------------------------------------------------+-------------------+--------------------+
>>>>>
>>>>> Fixes: a06157804399 ("mm/vmalloc: request large order pages from buddy allocator")
>>>>> Closes: https://lore.kernel.org/all/66919a28-bc81-49c9-b68f-dd7c73395a0d@arm.com/
>>>>> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
>>>>> Co-developed-by: Muhammad Usama Anjum <usama.anjum@arm.com>
>>>>> Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>
>>>>> ---
>>>>> Changes since v2:
>>>>> - Remove BUG_ON in favour of simple implementation as this has never
>>>>> been seen to output any bug in the past as well
>>>>> - Move the free loop to separate function, free_pages_bulk()
>>>>> - Update stats, lruvec_stat in separate loop
>>>>>
>>>>> Changes since v1:
>>>>> - Rebase on mm-new
>>>>> - Rerun benchmarks
>>>>>
>>>>> Made-with: Cursor
>>>>> ---
>>>>> include/linux/gfp.h | 2 ++
>>>>> mm/page_alloc.c | 23 +++++++++++++++++++++++
>>>>> mm/vmalloc.c | 16 +++++-----------
>>>>> 3 files changed, 30 insertions(+), 11 deletions(-)
>>>>>
>>>>> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
>>>>> index 7c1f9da7c8e56..71f9097ab99a0 100644
>>>>> --- a/include/linux/gfp.h
>>>>> +++ b/include/linux/gfp.h
>>>>> @@ -239,6 +239,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
>>>>> struct page **page_array);
>>>>> #define __alloc_pages_bulk(...) alloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))
>>>>>
>>>>> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages);
>>>>> +
>>>>> unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,
>>>>> unsigned long nr_pages,
>>>>> struct page **page_array);
>>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>>>> index eedce9a30eb7e..250cc07e547b8 100644
>>>>> --- a/mm/page_alloc.c
>>>>> +++ b/mm/page_alloc.c
>>>>> @@ -5175,6 +5175,29 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
>>>>> }
>>>>> EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);
>>>>>
>>>>> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages)
>>>>> +{
>>>>> + unsigned long start_pfn = 0, pfn;
>>>>> + unsigned long i, nr_contig = 0;
>>>>> +
>>>>> + for (i = 0; i < nr_pages; i++) {
>>>>> + pfn = page_to_pfn(page_array[i]);
>>>>> + if (!nr_contig) {
>>>>> + start_pfn = pfn;
>>>>> + nr_contig = 1;
>>>>> + } else if (start_pfn + nr_contig != pfn) {
>>>>> + __free_contig_range(start_pfn, nr_contig);
>>>>> + start_pfn = pfn;
>>>>> + nr_contig = 1;
>>>>> + cond_resched();
>>>>
>>> It will cause schedule while atomic. Have you checked that
>>> __free_contig_range() also can sleep? Of so then we are aligned, if not
>>> probably we should remove it.
>> Sorry, I didn't get it. How does having cond_resched() in this function
>> affects __free_contig_range()?
>>
> It is not. What i am asking is about:
>
> <snip>
> spin_lock();
> free_pages_bulk()
> ...
> <snip>
>
> so this is not allowed because there is cond_resched() call. We
> can remove it and make it possible to invoke free_pages_bulk() under
> spin-lock, __but__ only if for example other calls do not sleep:
>
> __free_contig_range()
> memdesc_section()
> free_prepared_contig_range()
> ...
>
>>
>> The current user of this function is only vfree() which is sleepable.
>>
> I know. But this function can be used by others soon or later.
>
> Another option is add a comment, saying that it is only for sleepable
> contexts.
Thank you for detailed response. I can move cond_resched() to vfree() and make
free_pages_bulk() allowed to be called form sleepable context. But I feel the
current implementation is better to avoid latency spikes. I'll put explicit
comment that this function can only be called from sleepable contexts.
Thanks,
Usama
>
> --
> Uladzislau Rezki
On 3/25/26 17:25, Muhammad Usama Anjum wrote: > On 25/03/2026 4:16 pm, Uladzislau Rezki wrote: >> On Wed, Mar 25, 2026 at 03:02:14PM +0000, Muhammad Usama Anjum wrote: >>> Sorry, I didn't get it. How does having cond_resched() in this function >>> affects __free_contig_range()? >>> >> It is not. What i am asking is about: >> >> <snip> >> spin_lock(); >> free_pages_bulk() >> ... >> <snip> >> >> so this is not allowed because there is cond_resched() call. We >> can remove it and make it possible to invoke free_pages_bulk() under >> spin-lock, __but__ only if for example other calls do not sleep: >> >> __free_contig_range() >> memdesc_section() >> free_prepared_contig_range() >> ... >> >>> >>> The current user of this function is only vfree() which is sleepable. >>> >> I know. But this function can be used by others soon or later. >> >> Another option is add a comment, saying that it is only for sleepable >> contexts. > Thank you for detailed response. I can move cond_resched() to vfree() and make > free_pages_bulk() allowed to be called form sleepable context. But I feel the > current implementation is better to avoid latency spikes. I'll put explicit > comment that this function can only be called from sleepable contexts. That's probably good enough for now. It can accept arbitrarily large areas, so the cond_resched() in there is the right thing to do. :) -- Cheers, David
On Wed, Mar 25, 2026 at 05:34:08PM +0100, David Hildenbrand (Arm) wrote: > On 3/25/26 17:25, Muhammad Usama Anjum wrote: > > On 25/03/2026 4:16 pm, Uladzislau Rezki wrote: > >> On Wed, Mar 25, 2026 at 03:02:14PM +0000, Muhammad Usama Anjum wrote: > >>> Sorry, I didn't get it. How does having cond_resched() in this function > >>> affects __free_contig_range()? > >>> > >> It is not. What i am asking is about: > >> > >> <snip> > >> spin_lock(); > >> free_pages_bulk() > >> ... > >> <snip> > >> > >> so this is not allowed because there is cond_resched() call. We > >> can remove it and make it possible to invoke free_pages_bulk() under > >> spin-lock, __but__ only if for example other calls do not sleep: > >> > >> __free_contig_range() > >> memdesc_section() > >> free_prepared_contig_range() > >> ... > >> > >>> > >>> The current user of this function is only vfree() which is sleepable. > >>> > >> I know. But this function can be used by others soon or later. > >> > >> Another option is add a comment, saying that it is only for sleepable > >> contexts. > > Thank you for detailed response. I can move cond_resched() to vfree() and make > > free_pages_bulk() allowed to be called form sleepable context. But I feel the > > current implementation is better to avoid latency spikes. I'll put explicit > > comment that this function can only be called from sleepable contexts. > Sounds good! > That's probably good enough for now. It can accept arbitrarily large > areas, so the cond_resched() in there is the right thing to do. :) > I agree, since it will be available for other callers, adding the comment is a right way, so people know :) -- Uladzislau Rezki
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