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

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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: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Yang Shi <yang.shi@linux.alibaba.com>
Acked-by: Kirill 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: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Rientjes 2020-04-06 20:04:28 -07:00 committed by Linus Torvalds
parent dcdf11ee14
commit 85b9f46e8e
5 changed files with 20 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
Documentation/admin-guide/mm/transhuge.rst
View File

@ -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.

3
include/linux/vm_event_item.h
View File

@ -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

2
mm/huge_memory.c
View File

@ -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;
}

4
mm/shmem.c
View File

@ -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,

2
mm/vmstat.c
View File

@ -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",