For reserved memory regions marked with this flag,
reserve_bootmem_region is not called during memmap_init_reserved_pages.
This can be used to avoid struct page initialization for
regions which won't need them, for e.g. hugepages with
HVO enabled.
Signed-off-by: Usama Arif <usama.arif@bytedance.com>
---
include/linux/memblock.h | 7 +++++++
mm/memblock.c | 32 ++++++++++++++++++++++++++------
2 files changed, 33 insertions(+), 6 deletions(-)
diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index f71ff9f0ec81..7f9d06c08592 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -47,6 +47,7 @@ enum memblock_flags {
MEMBLOCK_MIRROR = 0x2, /* mirrored region */
MEMBLOCK_NOMAP = 0x4, /* don't add to kernel direct mapping */
MEMBLOCK_DRIVER_MANAGED = 0x8, /* always detected via a driver */
+ MEMBLOCK_RSRV_NOINIT = 0x10, /* don't call reserve_bootmem_region for this region */
};
/**
@@ -125,6 +126,7 @@ int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
int memblock_mark_nomap(phys_addr_t base, phys_addr_t size);
int memblock_clear_nomap(phys_addr_t base, phys_addr_t size);
+int memblock_rsrv_mark_noinit(phys_addr_t base, phys_addr_t size);
void memblock_free_all(void);
void memblock_free(void *ptr, size_t size);
@@ -259,6 +261,11 @@ static inline bool memblock_is_nomap(struct memblock_region *m)
return m->flags & MEMBLOCK_NOMAP;
}
+static inline bool memblock_is_noinit(struct memblock_region *m)
+{
+ return m->flags & MEMBLOCK_RSRV_NOINIT;
+}
+
static inline bool memblock_is_driver_managed(struct memblock_region *m)
{
return m->flags & MEMBLOCK_DRIVER_MANAGED;
diff --git a/mm/memblock.c b/mm/memblock.c
index 4fd431d16ef2..3a15708af3b6 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -997,6 +997,22 @@ int __init_memblock memblock_clear_nomap(phys_addr_t base, phys_addr_t size)
return memblock_setclr_flag(base, size, 0, MEMBLOCK_NOMAP, 0);
}
+/**
+ * memblock_rsrv_mark_noinit - Mark a reserved memory region with flag MEMBLOCK_RSRV_NOINIT.
+ * @base: the base phys addr of the region
+ * @size: the size of the region
+ *
+ * For memory regions marked with %MEMBLOCK_RSRV_NOINIT, reserve_bootmem_region
+ * is not called during memmap_init_reserved_pages, hence struct pages are not
+ * initialized for this region.
+ *
+ * Return: 0 on success, -errno on failure.
+ */
+int __init_memblock memblock_rsrv_mark_noinit(phys_addr_t base, phys_addr_t size)
+{
+ return memblock_setclr_flag(base, size, 1, MEMBLOCK_RSRV_NOINIT, 1);
+}
+
static bool should_skip_region(struct memblock_type *type,
struct memblock_region *m,
int nid, int flags)
@@ -2113,13 +2129,17 @@ static void __init memmap_init_reserved_pages(void)
memblock_set_node(start, end, &memblock.reserved, nid);
}
- /* initialize struct pages for the reserved regions */
+ /*
+ * initialize struct pages for reserved regions that don't have
+ * the MEMBLOCK_RSRV_NOINIT flag set
+ */
for_each_reserved_mem_region(region) {
- nid = memblock_get_region_node(region);
- start = region->base;
- end = start + region->size;
-
- reserve_bootmem_region(start, end, nid);
+ if (!memblock_is_noinit(region)) {
+ nid = memblock_get_region_node(region);
+ start = region->base;
+ end = start + region->size;
+ reserve_bootmem_region(start, end, nid);
+ }
}
}
--
2.25.1On Thu, Jul 27, 2023 at 09:46:22PM +0100, Usama Arif wrote:
> For reserved memory regions marked with this flag,
> reserve_bootmem_region is not called during memmap_init_reserved_pages.
> This can be used to avoid struct page initialization for
> regions which won't need them, for e.g. hugepages with
> HVO enabled.
>
> Signed-off-by: Usama Arif <usama.arif@bytedance.com>
> ---
> include/linux/memblock.h | 7 +++++++
> mm/memblock.c | 32 ++++++++++++++++++++++++++------
> 2 files changed, 33 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index f71ff9f0ec81..7f9d06c08592 100644
> --e a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -47,6 +47,7 @@ enum memblock_flags {
> MEMBLOCK_MIRROR = 0x2, /* mirrored region */
> MEMBLOCK_NOMAP = 0x4, /* don't add to kernel direct mapping */
> MEMBLOCK_DRIVER_MANAGED = 0x8, /* always detected via a driver */
> + MEMBLOCK_RSRV_NOINIT = 0x10, /* don't call reserve_bootmem_region for this region */
The comment should reflect what it does, not how.
> };
>
> /**
> @@ -125,6 +126,7 @@ int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
> int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
> int memblock_mark_nomap(phys_addr_t base, phys_addr_t size);
> int memblock_clear_nomap(phys_addr_t base, phys_addr_t size);
> +int memblock_rsrv_mark_noinit(phys_addr_t base, phys_addr_t size);
Please spell out reserved here.
> void memblock_free_all(void);
> void memblock_free(void *ptr, size_t size);
> @@ -259,6 +261,11 @@ static inline bool memblock_is_nomap(struct memblock_region *m)
> return m->flags & MEMBLOCK_NOMAP;
> }
>
> +static inline bool memblock_is_noinit(struct memblock_region *m)
> +{
> + return m->flags & MEMBLOCK_RSRV_NOINIT;
> +}
> +
> static inline bool memblock_is_driver_managed(struct memblock_region *m)
> {
> return m->flags & MEMBLOCK_DRIVER_MANAGED;
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 4fd431d16ef2..3a15708af3b6 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -997,6 +997,22 @@ int __init_memblock memblock_clear_nomap(phys_addr_t base, phys_addr_t size)
> return memblock_setclr_flag(base, size, 0, MEMBLOCK_NOMAP, 0);
> }
>
> +/**
> + * memblock_rsrv_mark_noinit - Mark a reserved memory region with flag MEMBLOCK_RSRV_NOINIT.
> + * @base: the base phys addr of the region
> + * @size: the size of the region
> + *
> + * For memory regions marked with %MEMBLOCK_RSRV_NOINIT, reserve_bootmem_region
> + * is not called during memmap_init_reserved_pages, hence struct pages are not
> + * initialized for this region.
Here as well, the part of how is much less important. Here you should
emphasize that struct pages for MEMBLOCK_RSRV_NOINIT regions are not
initialized.
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +int __init_memblock memblock_rsrv_mark_noinit(phys_addr_t base, phys_addr_t size)
> +{
> + return memblock_setclr_flag(base, size, 1, MEMBLOCK_RSRV_NOINIT, 1);
> +}
> +
> static bool should_skip_region(struct memblock_type *type,
> struct memblock_region *m,
> int nid, int flags)
> @@ -2113,13 +2129,17 @@ static void __init memmap_init_reserved_pages(void)
> memblock_set_node(start, end, &memblock.reserved, nid);
> }
>
> - /* initialize struct pages for the reserved regions */
> + /*
> + * initialize struct pages for reserved regions that don't have
> + * the MEMBLOCK_RSRV_NOINIT flag set
> + */
> for_each_reserved_mem_region(region) {
> - nid = memblock_get_region_node(region);
> - start = region->base;
> - end = start + region->size;
> -
> - reserve_bootmem_region(start, end, nid);
> + if (!memblock_is_noinit(region)) {
> + nid = memblock_get_region_node(region);
> + start = region->base;
> + end = start + region->size;
Please keep the empty line here
> + reserve_bootmem_region(start, end, nid);
> + }
> }
> }
>
> --
> 2.25.1
>
--
Sincerely yours,
Mike.
Hi,
On 7/27/23 23:46, Usama Arif wrote:
> For reserved memory regions marked with this flag,
> reserve_bootmem_region is not called during memmap_init_reserved_pages.
> This can be used to avoid struct page initialization for
> regions which won't need them, for e.g. hugepages with
> HVO enabled.
>
> Signed-off-by: Usama Arif <usama.arif@bytedance.com>
> ---
> include/linux/memblock.h | 7 +++++++
> mm/memblock.c | 32 ++++++++++++++++++++++++++------
> 2 files changed, 33 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index f71ff9f0ec81..7f9d06c08592 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -47,6 +47,7 @@ enum memblock_flags {
> MEMBLOCK_MIRROR = 0x2, /* mirrored region */
> MEMBLOCK_NOMAP = 0x4, /* don't add to kernel direct mapping */
> MEMBLOCK_DRIVER_MANAGED = 0x8, /* always detected via a driver */
> + MEMBLOCK_RSRV_NOINIT = 0x10, /* don't call reserve_bootmem_region for this region */
> };
>
> /**
> @@ -125,6 +126,7 @@ int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
> int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
> int memblock_mark_nomap(phys_addr_t base, phys_addr_t size);
> int memblock_clear_nomap(phys_addr_t base, phys_addr_t size);
> +int memblock_rsrv_mark_noinit(phys_addr_t base, phys_addr_t size);
>
> void memblock_free_all(void);
> void memblock_free(void *ptr, size_t size);
> @@ -259,6 +261,11 @@ static inline bool memblock_is_nomap(struct memblock_region *m)
> return m->flags & MEMBLOCK_NOMAP;
> }
>
> +static inline bool memblock_is_noinit(struct memblock_region *m)
> +{
> + return m->flags & MEMBLOCK_RSRV_NOINIT;
> +}
> +
> static inline bool memblock_is_driver_managed(struct memblock_region *m)
> {
> return m->flags & MEMBLOCK_DRIVER_MANAGED;
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 4fd431d16ef2..3a15708af3b6 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -997,6 +997,22 @@ int __init_memblock memblock_clear_nomap(phys_addr_t base, phys_addr_t size)
> return memblock_setclr_flag(base, size, 0, MEMBLOCK_NOMAP, 0);
> }
>
> +/**
> + * memblock_rsrv_mark_noinit - Mark a reserved memory region with flag MEMBLOCK_RSRV_NOINIT.
> + * @base: the base phys addr of the region
> + * @size: the size of the region
> + *
> + * For memory regions marked with %MEMBLOCK_RSRV_NOINIT, reserve_bootmem_region
> + * is not called during memmap_init_reserved_pages, hence struct pages are not
> + * initialized for this region.
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +int __init_memblock memblock_rsrv_mark_noinit(phys_addr_t base, phys_addr_t size)
> +{
> + return memblock_setclr_flag(base, size, 1, MEMBLOCK_RSRV_NOINIT, 1);
> +}
> +
> static bool should_skip_region(struct memblock_type *type,
> struct memblock_region *m,
> int nid, int flags)
> @@ -2113,13 +2129,17 @@ static void __init memmap_init_reserved_pages(void)
> memblock_set_node(start, end, &memblock.reserved, nid);
> }
>
> - /* initialize struct pages for the reserved regions */
> + /*
> + * initialize struct pages for reserved regions that don't have
> + * the MEMBLOCK_RSRV_NOINIT flag set
> + */
> for_each_reserved_mem_region(region) {
> - nid = memblock_get_region_node(region);
> - start = region->base;
> - end = start + region->size;
> -
> - reserve_bootmem_region(start, end, nid);
> + if (!memblock_is_noinit(region)) {
> + nid = memblock_get_region_node(region);
> + start = region->base;
> + end = start + region->size;
> + reserve_bootmem_region(start, end, nid);
> + }
> }
> }
>
There's code like:
static inline void free_vmemmap_page(struct page *page)
{
if (PageReserved(page))
free_bootmem_page(page);
else
__free_page(page);
}
which depends on the PageReserved being in vmempages pages, so I think you can't skip that part?
--Mika
On 28/07/2023 05:30, Mika Penttilä wrote:
> Hi,
>
> On 7/27/23 23:46, Usama Arif wrote:
>
>> For reserved memory regions marked with this flag,
>> reserve_bootmem_region is not called during memmap_init_reserved_pages.
>> This can be used to avoid struct page initialization for
>> regions which won't need them, for e.g. hugepages with
>> HVO enabled.
>>
>> Signed-off-by: Usama Arif <usama.arif@bytedance.com>
>> ---
>> include/linux/memblock.h | 7 +++++++
>> mm/memblock.c | 32 ++++++++++++++++++++++++++------
>> 2 files changed, 33 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
>> index f71ff9f0ec81..7f9d06c08592 100644
>> --- a/include/linux/memblock.h
>> +++ b/include/linux/memblock.h
>> @@ -47,6 +47,7 @@ enum memblock_flags {
>> MEMBLOCK_MIRROR = 0x2, /* mirrored region */
>> MEMBLOCK_NOMAP = 0x4, /* don't add to kernel direct
>> mapping */
>> MEMBLOCK_DRIVER_MANAGED = 0x8, /* always detected via a
>> driver */
>> + MEMBLOCK_RSRV_NOINIT = 0x10, /* don't call
>> reserve_bootmem_region for this region */
>> };
>> /**
>> @@ -125,6 +126,7 @@ int memblock_clear_hotplug(phys_addr_t base,
>> phys_addr_t size);
>> int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
>> int memblock_mark_nomap(phys_addr_t base, phys_addr_t size);
>> int memblock_clear_nomap(phys_addr_t base, phys_addr_t size);
>> +int memblock_rsrv_mark_noinit(phys_addr_t base, phys_addr_t size);
>> void memblock_free_all(void);
>> void memblock_free(void *ptr, size_t size);
>> @@ -259,6 +261,11 @@ static inline bool memblock_is_nomap(struct
>> memblock_region *m)
>> return m->flags & MEMBLOCK_NOMAP;
>> }
>> +static inline bool memblock_is_noinit(struct memblock_region *m)
>> +{
>> + return m->flags & MEMBLOCK_RSRV_NOINIT;
>> +}
>> +
>> static inline bool memblock_is_driver_managed(struct memblock_region
>> *m)
>> {
>> return m->flags & MEMBLOCK_DRIVER_MANAGED;
>> diff --git a/mm/memblock.c b/mm/memblock.c
>> index 4fd431d16ef2..3a15708af3b6 100644
>> --- a/mm/memblock.c
>> +++ b/mm/memblock.c
>> @@ -997,6 +997,22 @@ int __init_memblock
>> memblock_clear_nomap(phys_addr_t base, phys_addr_t size)
>> return memblock_setclr_flag(base, size, 0, MEMBLOCK_NOMAP, 0);
>> }
>> +/**
>> + * memblock_rsrv_mark_noinit - Mark a reserved memory region with
>> flag MEMBLOCK_RSRV_NOINIT.
>> + * @base: the base phys addr of the region
>> + * @size: the size of the region
>> + *
>> + * For memory regions marked with %MEMBLOCK_RSRV_NOINIT,
>> reserve_bootmem_region
>> + * is not called during memmap_init_reserved_pages, hence struct
>> pages are not
>> + * initialized for this region.
>> + *
>> + * Return: 0 on success, -errno on failure.
>> + */
>> +int __init_memblock memblock_rsrv_mark_noinit(phys_addr_t base,
>> phys_addr_t size)
>> +{
>> + return memblock_setclr_flag(base, size, 1, MEMBLOCK_RSRV_NOINIT, 1);
>> +}
>> +
>> static bool should_skip_region(struct memblock_type *type,
>> struct memblock_region *m,
>> int nid, int flags)
>> @@ -2113,13 +2129,17 @@ static void __init
>> memmap_init_reserved_pages(void)
>> memblock_set_node(start, end, &memblock.reserved, nid);
>> }
>> - /* initialize struct pages for the reserved regions */
>> + /*
>> + * initialize struct pages for reserved regions that don't have
>> + * the MEMBLOCK_RSRV_NOINIT flag set
>> + */
>> for_each_reserved_mem_region(region) {
>> - nid = memblock_get_region_node(region);
>> - start = region->base;
>> - end = start + region->size;
>> -
>> - reserve_bootmem_region(start, end, nid);
>> + if (!memblock_is_noinit(region)) {
>> + nid = memblock_get_region_node(region);
>> + start = region->base;
>> + end = start + region->size;
>> + reserve_bootmem_region(start, end, nid);
>> + }
>> }
>> }
>
> There's code like:
>
> static inline void free_vmemmap_page(struct page *page)
> {
> if (PageReserved(page))
> free_bootmem_page(page);
> else
> __free_page(page);
> }
>
> which depends on the PageReserved being in vmempages pages, so I think
> you can't skip that part?
>
free_vmemmap_page_list (free_vmemmap_page) is called on struct pages
(refer to as [1]) that point to memory *which contains* the struct pages
(refer to as [2]) for the hugepage. The above if
(!memblock_is_noinit(region)) to not reserve_bootmem_region is called
for the struct pages [2] for the hugepage. struct pages [1] are not
changed with my patch.
As an experiment if I run the diff at the bottom with and without these
patches I get the same log "HugeTLB: reserved pages 4096, normal pages
0", which means those struct pages are treated the same without and
without these patches. (Its 4096 as 262144 struct pages [2] per hugepage
* 64 bytes per struct page / PAGE_SIZE = 4096 struct pages [1] )
Also should have mentioned in cover letter, I used cat /proc/meminfo to
make sure it was working as expected. Reserving 500 1G hugepages with
and without these patches when hugetlb_free_vmemmap=on
MemTotal: 536207112 kB (511.4G)
when hugetlb_free_vmemmap=off
MemTotal: 528015112 kB (503G)
The expectation is that for 500 1G hugepages, when using HVO we have a
saving of 16380K*500=~8GB which is what we see with and without those
patches (511.4G - 503G). These patches didnt affect these numbers.
diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index b5b7834e0f42..bc0ec90552b7 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -208,6 +208,8 @@ static int vmemmap_remap_range(unsigned long start,
unsigned long end,
return 0;
}
+static int i = 0, j = 0;
+
/*
* Free a vmemmap page. A vmemmap page can be allocated from the memblock
* allocator or buddy allocator. If the PG_reserved flag is set, it means
@@ -216,10 +218,14 @@ static int vmemmap_remap_range(unsigned long
start, unsigned long end,
*/
static inline void free_vmemmap_page(struct page *page)
{
- if (PageReserved(page))
+ if (PageReserved(page)) {
+ i++;
free_bootmem_page(page);
- else
+ }
+ else {
+ j++;
__free_page(page);
+ }
}
/* Free a list of the vmemmap pages */
@@ -380,6 +386,7 @@ static int vmemmap_remap_free(unsigned long start,
unsigned long end,
free_vmemmap_page_list(&vmemmap_pages);
+ pr_err("reserved pages %u, normal pages %u", i, j);
return ret;
}
> --Mika
>
>
On 7/28/23 16:47, Usama Arif wrote:
>
>
> On 28/07/2023 05:30, Mika Penttilä wrote:
>> Hi,
>>
>> On 7/27/23 23:46, Usama Arif wrote:
>>
>>> For reserved memory regions marked with this flag,
>>> reserve_bootmem_region is not called during memmap_init_reserved_pages.
>>> This can be used to avoid struct page initialization for
>>> regions which won't need them, for e.g. hugepages with
>>> HVO enabled.
>>>
>>> Signed-off-by: Usama Arif <usama.arif@bytedance.com>
>>> ---
>>> include/linux/memblock.h | 7 +++++++
>>> mm/memblock.c | 32 ++++++++++++++++++++++++++------
>>> 2 files changed, 33 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
>>> index f71ff9f0ec81..7f9d06c08592 100644
>>> --- a/include/linux/memblock.h
>>> +++ b/include/linux/memblock.h
>>> @@ -47,6 +47,7 @@ enum memblock_flags {
>>> MEMBLOCK_MIRROR = 0x2, /* mirrored region */
>>> MEMBLOCK_NOMAP = 0x4, /* don't add to kernel direct
>>> mapping */
>>> MEMBLOCK_DRIVER_MANAGED = 0x8, /* always detected via a
>>> driver */
>>> + MEMBLOCK_RSRV_NOINIT = 0x10, /* don't call
>>> reserve_bootmem_region for this region */
>>> };
>>> /**
>>> @@ -125,6 +126,7 @@ int memblock_clear_hotplug(phys_addr_t base,
>>> phys_addr_t size);
>>> int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
>>> int memblock_mark_nomap(phys_addr_t base, phys_addr_t size);
>>> int memblock_clear_nomap(phys_addr_t base, phys_addr_t size);
>>> +int memblock_rsrv_mark_noinit(phys_addr_t base, phys_addr_t size);
>>> void memblock_free_all(void);
>>> void memblock_free(void *ptr, size_t size);
>>> @@ -259,6 +261,11 @@ static inline bool memblock_is_nomap(struct
>>> memblock_region *m)
>>> return m->flags & MEMBLOCK_NOMAP;
>>> }
>>> +static inline bool memblock_is_noinit(struct memblock_region *m)
>>> +{
>>> + return m->flags & MEMBLOCK_RSRV_NOINIT;
>>> +}
>>> +
>>> static inline bool memblock_is_driver_managed(struct
>>> memblock_region *m)
>>> {
>>> return m->flags & MEMBLOCK_DRIVER_MANAGED;
>>> diff --git a/mm/memblock.c b/mm/memblock.c
>>> index 4fd431d16ef2..3a15708af3b6 100644
>>> --- a/mm/memblock.c
>>> +++ b/mm/memblock.c
>>> @@ -997,6 +997,22 @@ int __init_memblock
>>> memblock_clear_nomap(phys_addr_t base, phys_addr_t size)
>>> return memblock_setclr_flag(base, size, 0, MEMBLOCK_NOMAP, 0);
>>> }
>>> +/**
>>> + * memblock_rsrv_mark_noinit - Mark a reserved memory region with
>>> flag MEMBLOCK_RSRV_NOINIT.
>>> + * @base: the base phys addr of the region
>>> + * @size: the size of the region
>>> + *
>>> + * For memory regions marked with %MEMBLOCK_RSRV_NOINIT,
>>> reserve_bootmem_region
>>> + * is not called during memmap_init_reserved_pages, hence struct
>>> pages are not
>>> + * initialized for this region.
>>> + *
>>> + * Return: 0 on success, -errno on failure.
>>> + */
>>> +int __init_memblock memblock_rsrv_mark_noinit(phys_addr_t base,
>>> phys_addr_t size)
>>> +{
>>> + return memblock_setclr_flag(base, size, 1,
>>> MEMBLOCK_RSRV_NOINIT, 1);
>>> +}
>>> +
>>> static bool should_skip_region(struct memblock_type *type,
>>> struct memblock_region *m,
>>> int nid, int flags)
>>> @@ -2113,13 +2129,17 @@ static void __init
>>> memmap_init_reserved_pages(void)
>>> memblock_set_node(start, end, &memblock.reserved, nid);
>>> }
>>> - /* initialize struct pages for the reserved regions */
>>> + /*
>>> + * initialize struct pages for reserved regions that don't have
>>> + * the MEMBLOCK_RSRV_NOINIT flag set
>>> + */
>>> for_each_reserved_mem_region(region) {
>>> - nid = memblock_get_region_node(region);
>>> - start = region->base;
>>> - end = start + region->size;
>>> -
>>> - reserve_bootmem_region(start, end, nid);
>>> + if (!memblock_is_noinit(region)) {
>>> + nid = memblock_get_region_node(region);
>>> + start = region->base;
>>> + end = start + region->size;
>>> + reserve_bootmem_region(start, end, nid);
>>> + }
>>> }
>>> }
>>
>> There's code like:
>>
>> static inline void free_vmemmap_page(struct page *page)
>> {
>> if (PageReserved(page))
>> free_bootmem_page(page);
>> else
>> __free_page(page);
>> }
>>
>> which depends on the PageReserved being in vmempages pages, so I
>> think you can't skip that part?
>>
>
> free_vmemmap_page_list (free_vmemmap_page) is called on struct pages
> (refer to as [1]) that point to memory *which contains* the struct
> pages (refer to as [2]) for the hugepage. The above if
> (!memblock_is_noinit(region)) to not reserve_bootmem_region is called
> for the struct pages [2] for the hugepage. struct pages [1] are not
> changed with my patch.
>
> As an experiment if I run the diff at the bottom with and without
> these patches I get the same log "HugeTLB: reserved pages 4096, normal
> pages 0", which means those struct pages are treated the same without
> and without these patches. (Its 4096 as 262144 struct pages [2] per
> hugepage * 64 bytes per struct page / PAGE_SIZE = 4096 struct pages [1] )
>
> Also should have mentioned in cover letter, I used cat /proc/meminfo
> to make sure it was working as expected. Reserving 500 1G hugepages
> with and without these patches when hugetlb_free_vmemmap=on
> MemTotal: 536207112 kB (511.4G)
>
> when hugetlb_free_vmemmap=off
> MemTotal: 528015112 kB (503G)
>
>
> The expectation is that for 500 1G hugepages, when using HVO we have a
> saving of 16380K*500=~8GB which is what we see with and without those
> patches (511.4G - 503G). These patches didnt affect these numbers.
>
>
You are right, thanks for the explanation!
--Mika
>
> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> index b5b7834e0f42..bc0ec90552b7 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -208,6 +208,8 @@ static int vmemmap_remap_range(unsigned long
> start, unsigned long end,
> return 0;
> }
>
> +static int i = 0, j = 0;
> +
> /*
> * Free a vmemmap page. A vmemmap page can be allocated from the
> memblock
> * allocator or buddy allocator. If the PG_reserved flag is set, it
> means
> @@ -216,10 +218,14 @@ static int vmemmap_remap_range(unsigned long
> start, unsigned long end,
> */
> static inline void free_vmemmap_page(struct page *page)
> {
> - if (PageReserved(page))
> + if (PageReserved(page)) {
> + i++;
> free_bootmem_page(page);
> - else
> + }
> + else {
> + j++;
> __free_page(page);
> + }
> }
>
> /* Free a list of the vmemmap pages */
> @@ -380,6 +386,7 @@ static int vmemmap_remap_free(unsigned long start,
> unsigned long end,
>
> free_vmemmap_page_list(&vmemmap_pages);
>
> + pr_err("reserved pages %u, normal pages %u", i, j);
> return ret;
> }
>
>
>
>
>
>> --Mika
>>
>>
>
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