[patch 017/166] mm, shmem: add vmstat for hugepage fallback

Andrew Morton
2020-04-07T03:04:28Z

From: David Rientjes <rientjes@google.com>
Subject: mm, shmem: add vmstat for hugepage fallback

The existing thp_fault_fallback indicates when thp attempts to allocate a
hugepage but fails, or if the hugepage cannot be charged to the mem cgroup
hierarchy.

Extend this to shmem as well. Adds a new thp_file_fallback to complement
thp_file_alloc that gets incremented when a hugepage is attempted to be
allocated but fails, or if it cannot be charged to the mem cgroup
hierarchy.

Additionally, remove the check for CONFIG_TRANSPARENT_HUGE_PAGECACHE from
shmem_alloc_hugepage() since it is only called with this configuration
option.

Link: http://lkml.kernel.org/r/alpine.DEB.2.21.2003061421240.7412@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

Documentation/admin-guide/mm/transhuge.rst | 4 ++++
include/linux/vm_event_item.h | 2 ++
mm/shmem.c | 10 ++++++----
mm/vmstat.c | 1 +
4 files changed, 13 insertions(+), 4 deletions(-)

--- a/Documentation/admin-guide/mm/transhuge.rst~mm-shmem-add-vmstat-for-hugepage-fallback
+++ a/Documentation/admin-guide/mm/transhuge.rst
@@ -319,6 +319,10 @@ thp_file_alloc
is incremented every time a file huge page is successfully
allocated.

+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_mapped
is incremented every time a file huge page is mapped into
user address space.
--- a/include/linux/vm_event_item.h~mm-shmem-add-vmstat-for-hugepage-fallback
+++ a/include/linux/vm_event_item.h
@@ -76,6 +76,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PS
THP_COLLAPSE_ALLOC,
THP_COLLAPSE_ALLOC_FAILED,
THP_FILE_ALLOC,
+ THP_FILE_FALLBACK,
THP_FILE_MAPPED,
THP_SPLIT_PAGE,
THP_SPLIT_PAGE_FAILED,
@@ -115,6 +116,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PS

#ifndef CONFIG_TRANSPARENT_HUGEPAGE
#define THP_FILE_ALLOC ({ BUILD_BUG(); 0; })
+#define THP_FILE_FALLBACK ({ BUILD_BUG(); 0; })
#define THP_FILE_MAPPED ({ BUILD_BUG(); 0; })
#endif

--- a/mm/shmem.c~mm-shmem-add-vmstat-for-hugepage-fallback
+++ a/mm/shmem.c
@@ -1472,9 +1472,6 @@ static struct page *shmem_alloc_hugepage
pgoff_t hindex;
struct page *page;

- if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
- return NULL;
-
hindex = round_down(index, HPAGE_PMD_NR);
if (xa_find(&mapping->i_pages, &hindex, hindex + HPAGE_PMD_NR - 1,
XA_PRESENT))
@@ -1486,6 +1483,8 @@ static struct page *shmem_alloc_hugepage
shmem_pseudo_vma_destroy(&pvma);
if (page)
prep_transhuge_page(page);
+ else
+ count_vm_event(THP_FILE_FALLBACK);
return page;
}

@@ -1871,8 +1870,11 @@ alloc_nohuge:

error = mem_cgroup_try_charge_delay(page, charge_mm, gfp, &memcg,
PageTransHuge(page));
- if (error)
+ if (error) {
+ if (PageTransHuge(page))
+ count_vm_event(THP_FILE_FALLBACK);
goto unacct;
+ }
error = shmem_add_to_page_cache(page, mapping, hindex,
NULL, gfp & GFP_RECLAIM_MASK);
if (error) {
--- a/mm/vmstat.c~mm-shmem-add-vmstat-for-hugepage-fallback
+++ a/mm/vmstat.c
@@ -1259,6 +1259,7 @@ const char * const vmstat_text[] = {
"thp_collapse_alloc",
"thp_collapse_alloc_failed",
"thp_file_alloc",
+ "thp_file_fallback",
"thp_file_mapped",
"thp_split_page",
"thp_split_page_failed",
_