From: yangge yangge1116@126.com
Since commit 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations") no longer differentiates the migration type of pages in THP-sized PCP list, it's possible that non-movable allocation requests may get a CMA page from the list, in some cases, it's not acceptable.
If a large number of CMA memory are configured in system (for example, the CMA memory accounts for 50% of the system memory), starting a virtual machine with device passthrough will get stuck. During starting the virtual machine, it will call pin_user_pages_remote(..., FOLL_LONGTERM, ...) to pin memory. Normally if a page is present and in CMA area, pin_user_pages_remote() will migrate the page from CMA area to non-CMA area because of FOLL_LONGTERM flag. But if non-movable allocation requests return CMA memory, migrate_longterm_unpinnable_pages() will migrate a CMA page to another CMA page, which will fail to pass the check in check_and_migrate_movable_pages() and cause migration endless. Call trace: pin_user_pages_remote --__gup_longterm_locked // endless loops in this function ----_get_user_pages_locked ----check_and_migrate_movable_pages ------migrate_longterm_unpinnable_pages --------alloc_migration_target
This problem will also have a negative impact on CMA itself. For example, when CMA is borrowed by THP, and we need to reclaim it through cma_alloc() or dma_alloc_coherent(), we must move those pages out to ensure CMA's users can retrieve that contigous memory. Currently, CMA's memory is occupied by non-movable pages, meaning we can't relocate them. As a result, cma_alloc() is more likely to fail.
To fix the problem above, we add one PCP list for THP, which will not introduce a new cacheline for struct per_cpu_pages. THP will have 2 PCP lists, one PCP list is used by MOVABLE allocation, and the other PCP list is used by UNMOVABLE allocation. MOVABLE allocation contains GPF_MOVABLE, and UNMOVABLE allocation contains GFP_UNMOVABLE and GFP_RECLAIMABLE.
Fixes: 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations") Signed-off-by: yangge yangge1116@126.com --- include/linux/mmzone.h | 9 ++++----- mm/page_alloc.c | 9 +++++++-- 2 files changed, 11 insertions(+), 7 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index b7546dd..cb7f265 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -656,13 +656,12 @@ enum zone_watermarks { };
/* - * One per migratetype for each PAGE_ALLOC_COSTLY_ORDER. One additional list - * for THP which will usually be GFP_MOVABLE. Even if it is another type, - * it should not contribute to serious fragmentation causing THP allocation - * failures. + * One per migratetype for each PAGE_ALLOC_COSTLY_ORDER. Two additional lists + * are added for THP. One PCP list is used by GPF_MOVABLE, and the other PCP list + * is used by GFP_UNMOVABLE and GFP_RECLAIMABLE. */ #ifdef CONFIG_TRANSPARENT_HUGEPAGE -#define NR_PCP_THP 1 +#define NR_PCP_THP 2 #else #define NR_PCP_THP 0 #endif diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 8f416a0..0a837e6 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -504,10 +504,15 @@ static void bad_page(struct page *page, const char *reason)
static inline unsigned int order_to_pindex(int migratetype, int order) { + bool __maybe_unused movable; + #ifdef CONFIG_TRANSPARENT_HUGEPAGE if (order > PAGE_ALLOC_COSTLY_ORDER) { VM_BUG_ON(order != HPAGE_PMD_ORDER); - return NR_LOWORDER_PCP_LISTS; + + movable = migratetype == MIGRATE_MOVABLE; + + return NR_LOWORDER_PCP_LISTS + movable; } #else VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER); @@ -521,7 +526,7 @@ static inline int pindex_to_order(unsigned int pindex) int order = pindex / MIGRATE_PCPTYPES;
#ifdef CONFIG_TRANSPARENT_HUGEPAGE - if (pindex == NR_LOWORDER_PCP_LISTS) + if (pindex >= NR_LOWORDER_PCP_LISTS) order = HPAGE_PMD_ORDER; #else VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);
Hi,
Thanks for your patch.
FYI: kernel test robot notices the stable kernel rule is not satisfied.
The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html#opti...
Rule: add the tag "Cc: stable@vger.kernel.org" in the sign-off area to have the patch automatically included in the stable tree. Subject: [PATCH] mm/page_alloc: add one PCP list for THP Link: https://lore.kernel.org/stable/1718801672-30152-1-git-send-email-yangge1116%...
On Thu, Jun 20, 2024 at 12:55 AM yangge1116@126.com wrote:
From: yangge yangge1116@126.com
Since commit 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations") no longer differentiates the migration type of pages in THP-sized PCP list, it's possible that non-movable allocation requests may get a CMA page from the list, in some cases, it's not acceptable.
If a large number of CMA memory are configured in system (for example, the CMA memory accounts for 50% of the system memory), starting a virtual machine with device passthrough will get stuck. During starting the virtual machine, it will call pin_user_pages_remote(..., FOLL_LONGTERM, ...) to pin memory. Normally if a page is present and in CMA area, pin_user_pages_remote() will migrate the page from CMA area to non-CMA area because of FOLL_LONGTERM flag. But if non-movable allocation requests return CMA memory, migrate_longterm_unpinnable_pages() will migrate a CMA page to another CMA page, which will fail to pass the check in check_and_migrate_movable_pages() and cause migration endless. Call trace: pin_user_pages_remote --__gup_longterm_locked // endless loops in this function ----_get_user_pages_locked ----check_and_migrate_movable_pages ------migrate_longterm_unpinnable_pages --------alloc_migration_target
This problem will also have a negative impact on CMA itself. For example, when CMA is borrowed by THP, and we need to reclaim it through cma_alloc() or dma_alloc_coherent(), we must move those pages out to ensure CMA's users can retrieve that contigous memory. Currently, CMA's memory is occupied by non-movable pages, meaning we can't relocate them. As a result, cma_alloc() is more likely to fail.
To fix the problem above, we add one PCP list for THP, which will not introduce a new cacheline for struct per_cpu_pages. THP will have 2 PCP lists, one PCP list is used by MOVABLE allocation, and the other PCP list is used by UNMOVABLE allocation. MOVABLE allocation contains GPF_MOVABLE, and UNMOVABLE allocation contains GFP_UNMOVABLE and GFP_RECLAIMABLE.
Fixes: 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations")
Please add the below tag
And I don't think 'mm/page_alloc: add one PCP list for THP' is a good title. Maybe:
'mm/page_alloc: Separate THP PCP into movable and non-movable categories'
Whenever you send a new version, please add things like 'PATCH V2', 'PATCH V3'. You have already missed several version numbers, so we may have to start from V2 though V2 is wrong.
Signed-off-by: yangge yangge1116@126.com
include/linux/mmzone.h | 9 ++++----- mm/page_alloc.c | 9 +++++++-- 2 files changed, 11 insertions(+), 7 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index b7546dd..cb7f265 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -656,13 +656,12 @@ enum zone_watermarks { };
/*
- One per migratetype for each PAGE_ALLOC_COSTLY_ORDER. One additional list
- for THP which will usually be GFP_MOVABLE. Even if it is another type,
- it should not contribute to serious fragmentation causing THP allocation
- failures.
- One per migratetype for each PAGE_ALLOC_COSTLY_ORDER. Two additional lists
- are added for THP. One PCP list is used by GPF_MOVABLE, and the other PCP list
*/
- is used by GFP_UNMOVABLE and GFP_RECLAIMABLE.
#ifdef CONFIG_TRANSPARENT_HUGEPAGE -#define NR_PCP_THP 1 +#define NR_PCP_THP 2 #else #define NR_PCP_THP 0 #endif diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 8f416a0..0a837e6 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -504,10 +504,15 @@ static void bad_page(struct page *page, const char *reason)
static inline unsigned int order_to_pindex(int migratetype, int order) {
bool __maybe_unused movable;#ifdef CONFIG_TRANSPARENT_HUGEPAGE if (order > PAGE_ALLOC_COSTLY_ORDER) { VM_BUG_ON(order != HPAGE_PMD_ORDER);
return NR_LOWORDER_PCP_LISTS;
movable = migratetype == MIGRATE_MOVABLE;return NR_LOWORDER_PCP_LISTS + movable; }#else VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER); @@ -521,7 +526,7 @@ static inline int pindex_to_order(unsigned int pindex) int order = pindex / MIGRATE_PCPTYPES;
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
if (pindex == NR_LOWORDER_PCP_LISTS)
if (pindex >= NR_LOWORDER_PCP_LISTS) order = HPAGE_PMD_ORDER;#else VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER); -- 2.7.4
在 2024/6/20 6:28, Barry Song 写道:
On Thu, Jun 20, 2024 at 12:55 AM yangge1116@126.com wrote:
From: yangge yangge1116@126.com
Since commit 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations") no longer differentiates the migration type of pages in THP-sized PCP list, it's possible that non-movable allocation requests may get a CMA page from the list, in some cases, it's not acceptable.
If a large number of CMA memory are configured in system (for example, the CMA memory accounts for 50% of the system memory), starting a virtual machine with device passthrough will get stuck. During starting the virtual machine, it will call pin_user_pages_remote(..., FOLL_LONGTERM, ...) to pin memory. Normally if a page is present and in CMA area, pin_user_pages_remote() will migrate the page from CMA area to non-CMA area because of FOLL_LONGTERM flag. But if non-movable allocation requests return CMA memory, migrate_longterm_unpinnable_pages() will migrate a CMA page to another CMA page, which will fail to pass the check in check_and_migrate_movable_pages() and cause migration endless. Call trace: pin_user_pages_remote --__gup_longterm_locked // endless loops in this function ----_get_user_pages_locked ----check_and_migrate_movable_pages ------migrate_longterm_unpinnable_pages --------alloc_migration_target
This problem will also have a negative impact on CMA itself. For example, when CMA is borrowed by THP, and we need to reclaim it through cma_alloc() or dma_alloc_coherent(), we must move those pages out to ensure CMA's users can retrieve that contigous memory. Currently, CMA's memory is occupied by non-movable pages, meaning we can't relocate them. As a result, cma_alloc() is more likely to fail.
To fix the problem above, we add one PCP list for THP, which will not introduce a new cacheline for struct per_cpu_pages. THP will have 2 PCP lists, one PCP list is used by MOVABLE allocation, and the other PCP list is used by UNMOVABLE allocation. MOVABLE allocation contains GPF_MOVABLE, and UNMOVABLE allocation contains GFP_UNMOVABLE and GFP_RECLAIMABLE.
Fixes: 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations")
Please add the below tag
And I don't think 'mm/page_alloc: add one PCP list for THP' is a good title. Maybe:
'mm/page_alloc: Separate THP PCP into movable and non-movable categories'
Whenever you send a new version, please add things like 'PATCH V2', 'PATCH V3'. You have already missed several version numbers, so we may have to start from V2 though V2 is wrong.
Ok, thanks.
Signed-off-by: yangge yangge1116@126.com
include/linux/mmzone.h | 9 ++++----- mm/page_alloc.c | 9 +++++++-- 2 files changed, 11 insertions(+), 7 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index b7546dd..cb7f265 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -656,13 +656,12 @@ enum zone_watermarks { };
/*
- One per migratetype for each PAGE_ALLOC_COSTLY_ORDER. One additional list
- for THP which will usually be GFP_MOVABLE. Even if it is another type,
- it should not contribute to serious fragmentation causing THP allocation
- failures.
- One per migratetype for each PAGE_ALLOC_COSTLY_ORDER. Two additional lists
- are added for THP. One PCP list is used by GPF_MOVABLE, and the other PCP list
*/ #ifdef CONFIG_TRANSPARENT_HUGEPAGE
- is used by GFP_UNMOVABLE and GFP_RECLAIMABLE.
-#define NR_PCP_THP 1 +#define NR_PCP_THP 2 #else #define NR_PCP_THP 0 #endif diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 8f416a0..0a837e6 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -504,10 +504,15 @@ static void bad_page(struct page *page, const char *reason)
static inline unsigned int order_to_pindex(int migratetype, int order) {
bool __maybe_unused movable;- #ifdef CONFIG_TRANSPARENT_HUGEPAGE if (order > PAGE_ALLOC_COSTLY_ORDER) { VM_BUG_ON(order != HPAGE_PMD_ORDER);
return NR_LOWORDER_PCP_LISTS;
movable = migratetype == MIGRATE_MOVABLE;return NR_LOWORDER_PCP_LISTS + movable; }@@ -521,7 +526,7 @@ static inline int pindex_to_order(unsigned int pindex) int order = pindex / MIGRATE_PCPTYPES;
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
if (pindex == NR_LOWORDER_PCP_LISTS)
if (pindex >= NR_LOWORDER_PCP_LISTS) order = HPAGE_PMD_ORDER;-- 2.7.4
On Wed, 19 Jun 2024 20:54:32 +0800 yangge1116@126.com wrote:
From: yangge yangge1116@126.com
Since commit 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations") no longer differentiates the migration type of pages in THP-sized PCP list, it's possible that non-movable allocation requests may get a CMA page from the list, in some cases, it's not acceptable.
If a large number of CMA memory are configured in system (for example, the CMA memory accounts for 50% of the system memory), starting a virtual machine with device passthrough will get stuck. During starting the virtual machine, it will call pin_user_pages_remote(..., FOLL_LONGTERM, ...) to pin memory. Normally if a page is present and in CMA area, pin_user_pages_remote() will migrate the page from CMA area to non-CMA area because of FOLL_LONGTERM flag. But if non-movable allocation requests return CMA memory, migrate_longterm_unpinnable_pages() will migrate a CMA page to another CMA page, which will fail to pass the check in check_and_migrate_movable_pages() and cause migration endless. Call trace:
Thanks. I'll add this for testing - please send us a new version which addresses Barry's comments.
在 2024/6/20 9:01, Andrew Morton 写道:
On Wed, 19 Jun 2024 20:54:32 +0800 yangge1116@126.com wrote:
From: yangge yangge1116@126.com
Since commit 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations") no longer differentiates the migration type of pages in THP-sized PCP list, it's possible that non-movable allocation requests may get a CMA page from the list, in some cases, it's not acceptable.
If a large number of CMA memory are configured in system (for example, the CMA memory accounts for 50% of the system memory), starting a virtual machine with device passthrough will get stuck. During starting the virtual machine, it will call pin_user_pages_remote(..., FOLL_LONGTERM, ...) to pin memory. Normally if a page is present and in CMA area, pin_user_pages_remote() will migrate the page from CMA area to non-CMA area because of FOLL_LONGTERM flag. But if non-movable allocation requests return CMA memory, migrate_longterm_unpinnable_pages() will migrate a CMA page to another CMA page, which will fail to pass the check in check_and_migrate_movable_pages() and cause migration endless. Call trace:
Thanks. I'll add this for testing - please send us a new version which addresses Barry's comments.
Ok, thanks. New version: https://lore.kernel.org/lkml/1718845190-4456-1-git-send-email-yangge1116@126...
On Wed, Jun 19, 2024 at 08:54:32PM +0800, yangge1116@126.com wrote:
From: yangge yangge1116@126.com
Since commit 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations") no longer differentiates the migration type of pages in THP-sized PCP list, it's possible that non-movable allocation requests may get a CMA page from the list, in some cases, it's not acceptable.
If a large number of CMA memory are configured in system (for example, the CMA memory accounts for 50% of the system memory), starting a virtual machine with device passthrough will get stuck. During starting the virtual machine, it will call pin_user_pages_remote(..., FOLL_LONGTERM, ...) to pin memory. Normally if a page is present and in CMA area, pin_user_pages_remote() will migrate the page from CMA area to non-CMA area because of FOLL_LONGTERM flag. But if non-movable allocation requests return CMA memory, migrate_longterm_unpinnable_pages() will migrate a CMA page to another CMA page, which will fail to pass the check in check_and_migrate_movable_pages() and cause migration endless. Call trace: pin_user_pages_remote --__gup_longterm_locked // endless loops in this function ----_get_user_pages_locked ----check_and_migrate_movable_pages ------migrate_longterm_unpinnable_pages --------alloc_migration_target
This problem will also have a negative impact on CMA itself. For example, when CMA is borrowed by THP, and we need to reclaim it through cma_alloc() or dma_alloc_coherent(), we must move those pages out to ensure CMA's users can retrieve that contigous memory. Currently, CMA's memory is occupied by non-movable pages, meaning we can't relocate them. As a result, cma_alloc() is more likely to fail.
To fix the problem above, we add one PCP list for THP, which will not introduce a new cacheline for struct per_cpu_pages. THP will have 2 PCP lists, one PCP list is used by MOVABLE allocation, and the other PCP list is used by UNMOVABLE allocation. MOVABLE allocation contains GPF_MOVABLE, and UNMOVABLE allocation contains GFP_UNMOVABLE and GFP_RECLAIMABLE.
Fixes: 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations") Signed-off-by: yangge yangge1116@126.com
Too late to be relevant but
Acked-by: Mel Gorman mgorman@techsingularity.net
It would have been preferred if the comment stated why GFP_UNMOVABLE is needed because the original assumption that THP would mostly be MOVABLE allocations did not age well but git blame is enough. Maybe one day GFP_RECLAIMABLE will also be added to the list. However, I suspect the bigger problem later will be multiple THP sizes becoming more common that are not necessarily fitting within PAGE_ALLOC_COSTLY_ORDER and per-cpu not being enough to mitigate zone->lock contention in general. That's beyond the scope of this patch.
Thanks.
linux-stable-mirror@lists.linaro.org
-
Andrew Morton -
Barry Song -
Ge Yang -
kernel test robot -
Mel Gorman -
yangge1116＠126.com