Re: [PATCH v2 7/7] mm: shmem: add mTHP counters for anonymous shmem

From: Baolin Wang
Date: Tue May 14 2024 - 23:14:28 EST




On 2024/5/14 22:49, Lance Yang wrote:
Hi Baolin,

On Mon, May 13, 2024 at 1:08 PM Baolin Wang
<baolin.wang@xxxxxxxxxxxxxxxxx> wrote:

Add mTHP counters for anonymous shmem.

Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
---
include/linux/huge_mm.h | 3 +++
mm/huge_memory.c | 6 ++++++
mm/shmem.c | 18 +++++++++++++++---
3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index b5339210268d..e162498fef82 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -281,6 +281,9 @@ enum mthp_stat_item {
MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
MTHP_STAT_ANON_SWPOUT,
MTHP_STAT_ANON_SWPOUT_FALLBACK,
+ MTHP_STAT_FILE_ALLOC,
+ MTHP_STAT_FILE_FALLBACK,
+ MTHP_STAT_FILE_FALLBACK_CHARGE,
__MTHP_STAT_COUNT
};

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d3080a8843f2..fcda6ae604f6 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -555,6 +555,9 @@ DEFINE_MTHP_STAT_ATTR(anon_fault_fallback, MTHP_STAT_ANON_FAULT_FALLBACK);
DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
DEFINE_MTHP_STAT_ATTR(anon_swpout, MTHP_STAT_ANON_SWPOUT);
DEFINE_MTHP_STAT_ATTR(anon_swpout_fallback, MTHP_STAT_ANON_SWPOUT_FALLBACK);
+DEFINE_MTHP_STAT_ATTR(file_alloc, MTHP_STAT_FILE_ALLOC);
+DEFINE_MTHP_STAT_ATTR(file_fallback, MTHP_STAT_FILE_FALLBACK);
+DEFINE_MTHP_STAT_ATTR(file_fallback_charge, MTHP_STAT_FILE_FALLBACK_CHARGE);

static struct attribute *stats_attrs[] = {
&anon_fault_alloc_attr.attr,
@@ -562,6 +565,9 @@ static struct attribute *stats_attrs[] = {
&anon_fault_fallback_charge_attr.attr,
&anon_swpout_attr.attr,
&anon_swpout_fallback_attr.attr,
+ &file_alloc_attr.attr,
+ &file_fallback_attr.attr,
+ &file_fallback_charge_attr.attr,
NULL,
};

diff --git a/mm/shmem.c b/mm/shmem.c
index 8b020ff09c72..fd2cb2e73a21 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1786,6 +1786,9 @@ static struct folio *shmem_alloc_and_add_folio(struct vm_fault *vmf,

if (pages == HPAGE_PMD_NR)
count_vm_event(THP_FILE_FALLBACK);
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ count_mthp_stat(order, MTHP_STAT_FILE_FALLBACK);
+#endif

Seems like we don't need these conditional compilation directives here.

The THP_FILE_FALLBACK above will result in a compilation error if
CONFIG_TRANSPARENT_HUGEPAGE is not defined. So we don't
worry about that :)

See THP_FILE_FALLBACK in include/linux/vm_event_item.h.

order = next_order(&suitable_orders, order);
}
} else {
@@ -1805,9 +1808,15 @@ static struct folio *shmem_alloc_and_add_folio(struct vm_fault *vmf,
if (xa_find(&mapping->i_pages, &index,
index + pages - 1, XA_PRESENT)) {
error = -EEXIST;
- } else if (pages == HPAGE_PMD_NR) {
- count_vm_event(THP_FILE_FALLBACK);
- count_vm_event(THP_FILE_FALLBACK_CHARGE);
+ } else if (pages > 1) {
+ if (pages == HPAGE_PMD_NR) {
+ count_vm_event(THP_FILE_FALLBACK);
+ count_vm_event(THP_FILE_FALLBACK_CHARGE);
+ }
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ count_mthp_stat(folio_order(folio), MTHP_STAT_FILE_FALLBACK);
+ count_mthp_stat(folio_order(folio), MTHP_STAT_FILE_FALLBACK_CHARGE);
+#endif

As above.

}
goto unlock;
}
@@ -2178,6 +2187,9 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
if (!IS_ERR(folio)) {
if (folio_test_pmd_mappable(folio))
count_vm_event(THP_FILE_ALLOC);
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ count_mthp_stat(folio_order(folio), MTHP_STAT_FILE_ALLOC);
+#endif

As above.

Perhaps we need to define MTHP_STAT_FILE_ALLOC and friends
using a same way as THP_FILE_ALLOC, set as '{ BUILD_BUG(); 0; }'
If CONFIG_TRANSPARENT_HUGEPAGE is not defined.

Likely:

#ifndef CONFIG_TRANSPARENT_HUGEPAGE
#define MTHP_STAT_FILE_ALLOC ({ BUILD_BUG(); 0; })
...
#endif

This is not enough, and we should also define a dummy function for count_mthp_stat() when CONFIG_TRANSPARENT_HUGEPAGE is not enabled. I was also hesitant about doing this before, but adding macro controls seems relatively simple:)

Thanks for reviewing.