Commit 85b9f46e authored by David Rientjes's avatar David Rientjes Committed by Linus Torvalds
Browse files

mm, thp: track fallbacks due to failed memcg charges separately 



The thp_fault_fallback and thp_file_fallback vmstats are incremented if
either the hugepage allocation fails through the page allocator or the
hugepage charge fails through mem cgroup.

This patch leaves this field untouched but adds two new fields,
thp_{fault,file}_fallback_charge, which is incremented only when the mem
cgroup charge fails.

This distinguishes between attempted hugepage allocations that fail due to
fragmentation (or low memory conditions) and those that fail due to mem
cgroup limits.  That can be used to determine the impact of fragmentation
on the system by excluding faults that failed due to memcg usage.

Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarYang Shi <yang.shi@linux.alibaba.com>
Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Jeremy Cline <jcline@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: http://lkml.kernel.org/r/alpine.DEB.2.21.2003061422070.7412@chino.kir.corp.google.com


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent dcdf11ee

Documentation/admin-guide/mm/transhuge.rst

+10 −0
Original line number Diff line number Diff line
@@ -310,6 +310,11 @@ thp_fault_fallback 
	is incremented if a page fault fails to allocate

	a huge page and instead falls back to using small pages.



thp_fault_fallback_charge

	is incremented if a page fault fails to charge a huge page and

	instead falls back to using small pages even though the

	allocation was successful.



thp_collapse_alloc_failed

	is incremented if khugepaged found a range

	of pages that should be collapsed into one huge page but failed
@@ -323,6 +328,11 @@ thp_file_fallback 
	is incremented if a file huge page is attempted to be allocated

	but fails and instead falls back to using small pages.



thp_file_fallback_charge

	is incremented if a file huge page cannot be charged and instead

	falls back to using small pages even though the allocation was

	successful.



thp_file_mapped

	is incremented every time a file huge page is mapped into

	user address space.

include/linux/vm_event_item.h

+3 −0
Original line number Diff line number Diff line
@@ -73,10 +73,12 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, 
#ifdef CONFIG_TRANSPARENT_HUGEPAGE

		THP_FAULT_ALLOC,

		THP_FAULT_FALLBACK,

		THP_FAULT_FALLBACK_CHARGE,

		THP_COLLAPSE_ALLOC,

		THP_COLLAPSE_ALLOC_FAILED,

		THP_FILE_ALLOC,

		THP_FILE_FALLBACK,

		THP_FILE_FALLBACK_CHARGE,

		THP_FILE_MAPPED,

		THP_SPLIT_PAGE,

		THP_SPLIT_PAGE_FAILED,
@@ -117,6 +119,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, 
#ifndef CONFIG_TRANSPARENT_HUGEPAGE

#define THP_FILE_ALLOC ({ BUILD_BUG(); 0; })

#define THP_FILE_FALLBACK ({ BUILD_BUG(); 0; })

#define THP_FILE_FALLBACK_CHARGE ({ BUILD_BUG(); 0; })

#define THP_FILE_MAPPED ({ BUILD_BUG(); 0; })

#endif

mm/huge_memory.c

+2 −0
Original line number Diff line number Diff line
@@ -597,6 +597,7 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf, 
	if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {

		put_page(page);

		count_vm_event(THP_FAULT_FALLBACK);

		count_vm_event(THP_FAULT_FALLBACK_CHARGE);

		return VM_FAULT_FALLBACK;

	}
@@ -1446,6 +1447,7 @@ alloc: 
			put_page(page);

		ret |= VM_FAULT_FALLBACK;

		count_vm_event(THP_FAULT_FALLBACK);

		count_vm_event(THP_FAULT_FALLBACK_CHARGE);

		goto out;

	}

mm/shmem.c

+3 −1
Original line number Diff line number Diff line
@@ -1871,8 +1871,10 @@ alloc_nohuge: 
	error = mem_cgroup_try_charge_delay(page, charge_mm, gfp, &memcg,

					    PageTransHuge(page));

	if (error) {

		if (PageTransHuge(page))

		if (PageTransHuge(page)) {

			count_vm_event(THP_FILE_FALLBACK);

			count_vm_event(THP_FILE_FALLBACK_CHARGE);

		}

		goto unacct;

	}

	error = shmem_add_to_page_cache(page, mapping, hindex,

mm/vmstat.c

+2 −0
Original line number Diff line number Diff line
@@ -1256,10 +1256,12 @@ const char * const vmstat_text[] = { 
#ifdef CONFIG_TRANSPARENT_HUGEPAGE

	"thp_fault_alloc",

	"thp_fault_fallback",

	"thp_fault_fallback_charge",

	"thp_collapse_alloc",

	"thp_collapse_alloc_failed",

	"thp_file_alloc",

	"thp_file_fallback",

	"thp_file_fallback_charge",

	"thp_file_mapped",

	"thp_split_page",

	"thp_split_page_failed",

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