From: Zi Yan <ziy@nvidia.com>
migrate_pages() supports >0 order folio migration and during compaction,
even if compaction_alloc() cannot provide >0 order free pages,
migrate_pages() can split the source page and try to migrate the base pages
from the split. It can be a baseline and start point for adding support for
compacting >0 order folios.
Suggested-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Zi Yan <ziy@nvidia.com>
---
mm/compaction.c | 43 +++++++++++++++++++++++++++++++++++--------
1 file changed, 35 insertions(+), 8 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 4add68d40e8d..e43e898d2c77 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -816,6 +816,21 @@ static bool too_many_isolated(struct compact_control *cc)
return too_many;
}
+/*
+ * 1. if the page order is larger than or equal to target_order (i.e.,
+ * cc->order and when it is not -1 for global compaction), skip it since
+ * target_order already indicates no free page with larger than target_order
+ * exists and later migrating it will most likely fail;
+ *
+ * 2. compacting > pageblock_order pages does not improve memory fragmentation,
+ * skip them;
+ */
+static bool skip_isolation_on_order(int order, int target_order)
+{
+ return (target_order != -1 && order >= target_order) ||
+ order >= pageblock_order;
+}
+
/**
* isolate_migratepages_block() - isolate all migrate-able pages within
* a single pageblock
@@ -1010,7 +1025,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
/*
* Regardless of being on LRU, compound pages such as THP and
* hugetlbfs are not to be compacted unless we are attempting
- * an allocation much larger than the huge page size (eg CMA).
+ * an allocation larger than the compound page size.
* We can potentially save a lot of iterations if we skip them
* at once. The check is racy, but we can consider only valid
* values and the only danger is skipping too much.
@@ -1018,11 +1033,18 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
if (PageCompound(page) && !cc->alloc_contig) {
const unsigned int order = compound_order(page);
- if (likely(order <= MAX_PAGE_ORDER)) {
- low_pfn += (1UL << order) - 1;
- nr_scanned += (1UL << order) - 1;
+ /*
+ * Skip based on page order and compaction target order
+ * and skip hugetlbfs pages.
+ */
+ if (skip_isolation_on_order(order, cc->order) ||
+ PageHuge(page)) {
+ if (order <= MAX_PAGE_ORDER) {
+ low_pfn += (1UL << order) - 1;
+ nr_scanned += (1UL << order) - 1;
+ }
+ goto isolate_fail;
}
- goto isolate_fail;
}
/*
@@ -1165,10 +1187,11 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
}
/*
- * folio become large since the non-locked check,
- * and it's on LRU.
+ * Check LRU folio order under the lock
*/
- if (unlikely(folio_test_large(folio) && !cc->alloc_contig)) {
+ if (unlikely(skip_isolation_on_order(folio_order(folio),
+ cc->order) &&
+ !cc->alloc_contig)) {
low_pfn += folio_nr_pages(folio) - 1;
nr_scanned += folio_nr_pages(folio) - 1;
folio_set_lru(folio);
@@ -1786,6 +1809,10 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data)
struct compact_control *cc = (struct compact_control *)data;
struct folio *dst;
+ /* this makes migrate_pages() split the source page and retry */
+ if (folio_test_large(src) > 0)
+ return NULL;
+
if (list_empty(&cc->freepages)) {
isolate_freepages(cc);
--
2.43.0On 2/2/24 17:15, Zi Yan wrote:
> From: Zi Yan <ziy@nvidia.com>
>
> migrate_pages() supports >0 order folio migration and during compaction,
> even if compaction_alloc() cannot provide >0 order free pages,
> migrate_pages() can split the source page and try to migrate the base pages
> from the split. It can be a baseline and start point for adding support for
> compacting >0 order folios.
>
> Suggested-by: Huang Ying <ying.huang@intel.com>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
> mm/compaction.c | 43 +++++++++++++++++++++++++++++++++++--------
> 1 file changed, 35 insertions(+), 8 deletions(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 4add68d40e8d..e43e898d2c77 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -816,6 +816,21 @@ static bool too_many_isolated(struct compact_control *cc)
> return too_many;
> }
>
> +/*
> + * 1. if the page order is larger than or equal to target_order (i.e.,
> + * cc->order and when it is not -1 for global compaction), skip it since
> + * target_order already indicates no free page with larger than target_order
> + * exists and later migrating it will most likely fail;
> + *
> + * 2. compacting > pageblock_order pages does not improve memory fragmentation,
> + * skip them;
> + */
> +static bool skip_isolation_on_order(int order, int target_order)
> +{
> + return (target_order != -1 && order >= target_order) ||
> + order >= pageblock_order;
> +}
> +
> /**
> * isolate_migratepages_block() - isolate all migrate-able pages within
> * a single pageblock
> @@ -1010,7 +1025,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
> /*
> * Regardless of being on LRU, compound pages such as THP and
> * hugetlbfs are not to be compacted unless we are attempting
> - * an allocation much larger than the huge page size (eg CMA).
> + * an allocation larger than the compound page size.
> * We can potentially save a lot of iterations if we skip them
> * at once. The check is racy, but we can consider only valid
> * values and the only danger is skipping too much.
> @@ -1018,11 +1033,18 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
> if (PageCompound(page) && !cc->alloc_contig) {
> const unsigned int order = compound_order(page);
>
> - if (likely(order <= MAX_PAGE_ORDER)) {
> - low_pfn += (1UL << order) - 1;
> - nr_scanned += (1UL << order) - 1;
> + /*
> + * Skip based on page order and compaction target order
> + * and skip hugetlbfs pages.
> + */
> + if (skip_isolation_on_order(order, cc->order) ||
> + PageHuge(page)) {
Hm I'd try to avoid a new PageHuge() test here.
Earlier we have a block that does
if (PageHuge(page) && cc->alloc_contig) {
...
think I'd rather rewrite it to handle the PageHuge() case completely and
just make it skip the 1UL << order pages there for !cc->alloc_config. Even
if it means duplicating a bit of the low_pfn and nr_scanned bumping code.
Which reminds me the PageHuge() check there is probably still broken ATM:
https://lore.kernel.org/all/8fa1c95c-4749-33dd-42ba-243e492ab109@suse.cz/
Even better reason not to add another one.
If the huge page materialized since the first check, we should bail out when
testing PageLRU later anyway.
> + if (order <= MAX_PAGE_ORDER) {
> + low_pfn += (1UL << order) - 1;
> + nr_scanned += (1UL << order) - 1;
> + }
> + goto isolate_fail;
> }
> - goto isolate_fail;
> }
>
> /*
> @@ -1165,10 +1187,11 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
> }
>
> /*
> - * folio become large since the non-locked check,
> - * and it's on LRU.
> + * Check LRU folio order under the lock
> */
> - if (unlikely(folio_test_large(folio) && !cc->alloc_contig)) {
> + if (unlikely(skip_isolation_on_order(folio_order(folio),
> + cc->order) &&
> + !cc->alloc_contig)) {
> low_pfn += folio_nr_pages(folio) - 1;
> nr_scanned += folio_nr_pages(folio) - 1;
> folio_set_lru(folio);
> @@ -1786,6 +1809,10 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data)
> struct compact_control *cc = (struct compact_control *)data;
> struct folio *dst;
>
> + /* this makes migrate_pages() split the source page and retry */
> + if (folio_test_large(src) > 0)
> + return NULL;
> +
> if (list_empty(&cc->freepages)) {
> isolate_freepages(cc);
>
On 9 Feb 2024, at 9:32, Vlastimil Babka wrote:
> On 2/2/24 17:15, Zi Yan wrote:
>> From: Zi Yan <ziy@nvidia.com>
>>
>> migrate_pages() supports >0 order folio migration and during compaction,
>> even if compaction_alloc() cannot provide >0 order free pages,
>> migrate_pages() can split the source page and try to migrate the base pages
>> from the split. It can be a baseline and start point for adding support for
>> compacting >0 order folios.
>>
>> Suggested-by: Huang Ying <ying.huang@intel.com>
>> Signed-off-by: Zi Yan <ziy@nvidia.com>
>> ---
>> mm/compaction.c | 43 +++++++++++++++++++++++++++++++++++--------
>> 1 file changed, 35 insertions(+), 8 deletions(-)
>>
>> diff --git a/mm/compaction.c b/mm/compaction.c
>> index 4add68d40e8d..e43e898d2c77 100644
>> --- a/mm/compaction.c
>> +++ b/mm/compaction.c
>> @@ -816,6 +816,21 @@ static bool too_many_isolated(struct compact_control *cc)
>> return too_many;
>> }
>>
>> +/*
>> + * 1. if the page order is larger than or equal to target_order (i.e.,
>> + * cc->order and when it is not -1 for global compaction), skip it since
>> + * target_order already indicates no free page with larger than target_order
>> + * exists and later migrating it will most likely fail;
>> + *
>> + * 2. compacting > pageblock_order pages does not improve memory fragmentation,
>> + * skip them;
>> + */
>> +static bool skip_isolation_on_order(int order, int target_order)
>> +{
>> + return (target_order != -1 && order >= target_order) ||
>> + order >= pageblock_order;
>> +}
>> +
>> /**
>> * isolate_migratepages_block() - isolate all migrate-able pages within
>> * a single pageblock
>> @@ -1010,7 +1025,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
>> /*
>> * Regardless of being on LRU, compound pages such as THP and
>> * hugetlbfs are not to be compacted unless we are attempting
>> - * an allocation much larger than the huge page size (eg CMA).
>> + * an allocation larger than the compound page size.
>> * We can potentially save a lot of iterations if we skip them
>> * at once. The check is racy, but we can consider only valid
>> * values and the only danger is skipping too much.
>> @@ -1018,11 +1033,18 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
>> if (PageCompound(page) && !cc->alloc_contig) {
>> const unsigned int order = compound_order(page);
>>
>> - if (likely(order <= MAX_PAGE_ORDER)) {
>> - low_pfn += (1UL << order) - 1;
>> - nr_scanned += (1UL << order) - 1;
>> + /*
>> + * Skip based on page order and compaction target order
>> + * and skip hugetlbfs pages.
>> + */
>> + if (skip_isolation_on_order(order, cc->order) ||
>> + PageHuge(page)) {
>
> Hm I'd try to avoid a new PageHuge() test here.
>
> Earlier we have a block that does
> if (PageHuge(page) && cc->alloc_contig) {
> ...
>
> think I'd rather rewrite it to handle the PageHuge() case completely and
> just make it skip the 1UL << order pages there for !cc->alloc_config. Even
> if it means duplicating a bit of the low_pfn and nr_scanned bumping code.
>
> Which reminds me the PageHuge() check there is probably still broken ATM:
>
> https://lore.kernel.org/all/8fa1c95c-4749-33dd-42ba-243e492ab109@suse.cz/
>
> Even better reason not to add another one.
> If the huge page materialized since the first check, we should bail out when
> testing PageLRU later anyway.
OK, so basically something like:
if (PageHuge(page)) {
if (cc->alloc_contig) {
// existing code for PageHuge(page) && cc->allc_contig
} else {
const unsigned int order = compound_order(page);
if (order <= MAX_PAGE_ORDER) {
low_pfn += (1UL << order) - 1;
nr_scanned += (1UL << order) - 1;
}
goto isolate_fail;
}
}
...
if (PageCompound(page) && !cc->alloc_contig) {
const unsigned int order = compound_order(page);
/* Skip based on page order and compaction target order. */
if (skip_isolation_on_order(order, cc->order)) {
if (order <= MAX_PAGE_ORDER) {
low_pfn += (1UL << order) - 1;
nr_scanned += (1UL << order) - 1;
}
goto isolate_fail;
}
}
>
>> + if (order <= MAX_PAGE_ORDER) {
>> + low_pfn += (1UL << order) - 1;
>> + nr_scanned += (1UL << order) - 1;
>> + }
>> + goto isolate_fail;
>> }
>> - goto isolate_fail;
>> }
>>
>> /*
>> @@ -1165,10 +1187,11 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
>> }
>>
>> /*
>> - * folio become large since the non-locked check,
>> - * and it's on LRU.
>> + * Check LRU folio order under the lock
>> */
>> - if (unlikely(folio_test_large(folio) && !cc->alloc_contig)) {
>> + if (unlikely(skip_isolation_on_order(folio_order(folio),
>> + cc->order) &&
>> + !cc->alloc_contig)) {
>> low_pfn += folio_nr_pages(folio) - 1;
>> nr_scanned += folio_nr_pages(folio) - 1;
>> folio_set_lru(folio);
>> @@ -1786,6 +1809,10 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data)
>> struct compact_control *cc = (struct compact_control *)data;
>> struct folio *dst;
>>
>> + /* this makes migrate_pages() split the source page and retry */
>> + if (folio_test_large(src) > 0)
>> + return NULL;
>> +
>> if (list_empty(&cc->freepages)) {
>> isolate_freepages(cc);
>>
--
Best Regards,
Yan, Zi
On 2/9/24 20:25, Zi Yan wrote:
> On 9 Feb 2024, at 9:32, Vlastimil Babka wrote:
>
>> On 2/2/24 17:15, Zi Yan wrote:
>>> From: Zi Yan <ziy@nvidia.com>
>>>
>>> migrate_pages() supports >0 order folio migration and during compaction,
>>> even if compaction_alloc() cannot provide >0 order free pages,
>>> migrate_pages() can split the source page and try to migrate the base pages
>>> from the split. It can be a baseline and start point for adding support for
>>> compacting >0 order folios.
>>>
>>> Suggested-by: Huang Ying <ying.huang@intel.com>
>>> Signed-off-by: Zi Yan <ziy@nvidia.com>
>>> ---
>>> mm/compaction.c | 43 +++++++++++++++++++++++++++++++++++--------
>>> 1 file changed, 35 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/mm/compaction.c b/mm/compaction.c
>>> index 4add68d40e8d..e43e898d2c77 100644
>>> --- a/mm/compaction.c
>>> +++ b/mm/compaction.c
>>> @@ -816,6 +816,21 @@ static bool too_many_isolated(struct compact_control *cc)
>>> return too_many;
>>> }
>>>
>>> +/*
>>> + * 1. if the page order is larger than or equal to target_order (i.e.,
>>> + * cc->order and when it is not -1 for global compaction), skip it since
>>> + * target_order already indicates no free page with larger than target_order
>>> + * exists and later migrating it will most likely fail;
>>> + *
>>> + * 2. compacting > pageblock_order pages does not improve memory fragmentation,
>>> + * skip them;
>>> + */
>>> +static bool skip_isolation_on_order(int order, int target_order)
>>> +{
>>> + return (target_order != -1 && order >= target_order) ||
>>> + order >= pageblock_order;
>>> +}
>>> +
>>> /**
>>> * isolate_migratepages_block() - isolate all migrate-able pages within
>>> * a single pageblock
>>> @@ -1010,7 +1025,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
>>> /*
>>> * Regardless of being on LRU, compound pages such as THP and
>>> * hugetlbfs are not to be compacted unless we are attempting
>>> - * an allocation much larger than the huge page size (eg CMA).
>>> + * an allocation larger than the compound page size.
>>> * We can potentially save a lot of iterations if we skip them
>>> * at once. The check is racy, but we can consider only valid
>>> * values and the only danger is skipping too much.
>>> @@ -1018,11 +1033,18 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
>>> if (PageCompound(page) && !cc->alloc_contig) {
>>> const unsigned int order = compound_order(page);
>>>
>>> - if (likely(order <= MAX_PAGE_ORDER)) {
>>> - low_pfn += (1UL << order) - 1;
>>> - nr_scanned += (1UL << order) - 1;
>>> + /*
>>> + * Skip based on page order and compaction target order
>>> + * and skip hugetlbfs pages.
>>> + */
>>> + if (skip_isolation_on_order(order, cc->order) ||
>>> + PageHuge(page)) {
>>
>> Hm I'd try to avoid a new PageHuge() test here.
>>
>> Earlier we have a block that does
>> if (PageHuge(page) && cc->alloc_contig) {
>> ...
>>
>> think I'd rather rewrite it to handle the PageHuge() case completely and
>> just make it skip the 1UL << order pages there for !cc->alloc_config. Even
>> if it means duplicating a bit of the low_pfn and nr_scanned bumping code.
>>
>> Which reminds me the PageHuge() check there is probably still broken ATM:
>>
>> https://lore.kernel.org/all/8fa1c95c-4749-33dd-42ba-243e492ab109@suse.cz/
>>
>> Even better reason not to add another one.
>> If the huge page materialized since the first check, we should bail out when
>> testing PageLRU later anyway.
>
>
> OK, so basically something like:
>
> if (PageHuge(page)) {
> if (cc->alloc_contig) {
Yeah but I'd handle the !cc->alloc_contig first as that ends with a goto,
and then the rest doesn't need to be "} else { ... }" with extra identation
> // existing code for PageHuge(page) && cc->allc_contig
> } else {
> const unsigned int order = compound_order(page);
>
> if (order <= MAX_PAGE_ORDER) {
> low_pfn += (1UL << order) - 1;
> nr_scanned += (1UL << order) - 1;
> }
> goto isolate_fail;
> }
> }
On 9 Feb 2024, at 15:43, Vlastimil Babka wrote:
> On 2/9/24 20:25, Zi Yan wrote:
>> On 9 Feb 2024, at 9:32, Vlastimil Babka wrote:
>>
>>> On 2/2/24 17:15, Zi Yan wrote:
>>>> From: Zi Yan <ziy@nvidia.com>
>>>>
>>>> migrate_pages() supports >0 order folio migration and during compaction,
>>>> even if compaction_alloc() cannot provide >0 order free pages,
>>>> migrate_pages() can split the source page and try to migrate the base pages
>>>> from the split. It can be a baseline and start point for adding support for
>>>> compacting >0 order folios.
>>>>
>>>> Suggested-by: Huang Ying <ying.huang@intel.com>
>>>> Signed-off-by: Zi Yan <ziy@nvidia.com>
>>>> ---
>>>> mm/compaction.c | 43 +++++++++++++++++++++++++++++++++++--------
>>>> 1 file changed, 35 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/mm/compaction.c b/mm/compaction.c
>>>> index 4add68d40e8d..e43e898d2c77 100644
>>>> --- a/mm/compaction.c
>>>> +++ b/mm/compaction.c
>>>> @@ -816,6 +816,21 @@ static bool too_many_isolated(struct compact_control *cc)
>>>> return too_many;
>>>> }
>>>>
>>>> +/*
>>>> + * 1. if the page order is larger than or equal to target_order (i.e.,
>>>> + * cc->order and when it is not -1 for global compaction), skip it since
>>>> + * target_order already indicates no free page with larger than target_order
>>>> + * exists and later migrating it will most likely fail;
>>>> + *
>>>> + * 2. compacting > pageblock_order pages does not improve memory fragmentation,
>>>> + * skip them;
>>>> + */
>>>> +static bool skip_isolation_on_order(int order, int target_order)
>>>> +{
>>>> + return (target_order != -1 && order >= target_order) ||
>>>> + order >= pageblock_order;
>>>> +}
>>>> +
>>>> /**
>>>> * isolate_migratepages_block() - isolate all migrate-able pages within
>>>> * a single pageblock
>>>> @@ -1010,7 +1025,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
>>>> /*
>>>> * Regardless of being on LRU, compound pages such as THP and
>>>> * hugetlbfs are not to be compacted unless we are attempting
>>>> - * an allocation much larger than the huge page size (eg CMA).
>>>> + * an allocation larger than the compound page size.
>>>> * We can potentially save a lot of iterations if we skip them
>>>> * at once. The check is racy, but we can consider only valid
>>>> * values and the only danger is skipping too much.
>>>> @@ -1018,11 +1033,18 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
>>>> if (PageCompound(page) && !cc->alloc_contig) {
>>>> const unsigned int order = compound_order(page);
>>>>
>>>> - if (likely(order <= MAX_PAGE_ORDER)) {
>>>> - low_pfn += (1UL << order) - 1;
>>>> - nr_scanned += (1UL << order) - 1;
>>>> + /*
>>>> + * Skip based on page order and compaction target order
>>>> + * and skip hugetlbfs pages.
>>>> + */
>>>> + if (skip_isolation_on_order(order, cc->order) ||
>>>> + PageHuge(page)) {
>>>
>>> Hm I'd try to avoid a new PageHuge() test here.
>>>
>>> Earlier we have a block that does
>>> if (PageHuge(page) && cc->alloc_contig) {
>>> ...
>>>
>>> think I'd rather rewrite it to handle the PageHuge() case completely and
>>> just make it skip the 1UL << order pages there for !cc->alloc_config. Even
>>> if it means duplicating a bit of the low_pfn and nr_scanned bumping code.
>>>
>>> Which reminds me the PageHuge() check there is probably still broken ATM:
>>>
>>> https://lore.kernel.org/all/8fa1c95c-4749-33dd-42ba-243e492ab109@suse.cz/
>>>
>>> Even better reason not to add another one.
>>> If the huge page materialized since the first check, we should bail out when
>>> testing PageLRU later anyway.
>>
>>
>> OK, so basically something like:
>>
>> if (PageHuge(page)) {
>> if (cc->alloc_contig) {
>
> Yeah but I'd handle the !cc->alloc_contig first as that ends with a goto,
> and then the rest doesn't need to be "} else { ... }" with extra identation
OK. No problem.
--
Best Regards,
Yan, Zi
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