[RFC PATCH v1 4/4] mm: page_io: Count successful mTHP zswap stores in vmstat.

From: Kanchana P Sridhar
Date: Wed Aug 14 2024 - 02:29:07 EST


Added count_zswap_thp_swpout_vm_event() that will increment the
appropriate mTHP/PMD vmstat event counters if zswap_store succeeds for
a large folio:

zswap_store mTHP order [0, HPAGE_PMD_ORDER-1] will increment these
vmstat event counters:

ZSWPOUT_4KB_FOLIO
mTHP_ZSWPOUT_8kB
mTHP_ZSWPOUT_16kB
mTHP_ZSWPOUT_32kB
mTHP_ZSWPOUT_64kB
mTHP_ZSWPOUT_128kB
mTHP_ZSWPOUT_256kB
mTHP_ZSWPOUT_512kB
mTHP_ZSWPOUT_1024kB

zswap_store of a PMD-size THP, i.e., mTHP order HPAGE_PMD_ORDER, will
increment both these vmstat event counters:

ZSWPOUT_PMD_THP_FOLIO
mTHP_ZSWPOUT_2048kB

Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@xxxxxxxxx>
---
mm/page_io.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)

diff --git a/mm/page_io.c b/mm/page_io.c
index 0a150c240bf4..ab54d2060cc4 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -172,6 +172,49 @@ int generic_swapfile_activate(struct swap_info_struct *sis,
goto out;
}

+/*
+ * Count vmstats for ZSWAP store of large folios (mTHP and PMD-size THP).
+ */
+static inline void count_zswap_thp_swpout_vm_event(struct folio *folio)
+{
+ if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && folio_test_pmd_mappable(folio)) {
+ count_vm_event(ZSWPOUT_PMD_THP_FOLIO);
+ count_vm_event(mTHP_ZSWPOUT_2048kB);
+ } else if (folio_order(folio) == 0) {
+ count_vm_event(ZSWPOUT_4KB_FOLIO);
+ } else if (IS_ENABLED(CONFIG_THP_SWAP)) {
+ switch (folio_order(folio)) {
+ case 1:
+ count_vm_event(mTHP_ZSWPOUT_8kB);
+ break;
+ case 2:
+ count_vm_event(mTHP_ZSWPOUT_16kB);
+ break;
+ case 3:
+ count_vm_event(mTHP_ZSWPOUT_32kB);
+ break;
+ case 4:
+ count_vm_event(mTHP_ZSWPOUT_64kB);
+ break;
+ case 5:
+ count_vm_event(mTHP_ZSWPOUT_128kB);
+ break;
+ case 6:
+ count_vm_event(mTHP_ZSWPOUT_256kB);
+ break;
+ case 7:
+ count_vm_event(mTHP_ZSWPOUT_512kB);
+ break;
+ case 8:
+ count_vm_event(mTHP_ZSWPOUT_1024kB);
+ break;
+ case 9:
+ count_vm_event(mTHP_ZSWPOUT_2048kB);
+ break;
+ }
+ }
+}
+
/*
* We may have stale swap cache pages in memory: notice
* them here and get rid of the unnecessary final write.
@@ -196,6 +239,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
return ret;
}
if (zswap_store(folio)) {
+ count_zswap_thp_swpout_vm_event(folio);
folio_start_writeback(folio);
folio_unlock(folio);
folio_end_writeback(folio);
--
2.27.0