linux-kernel - [PATCH v2 4/4] mm: swap: Count successful mTHP ZSWAP stores in sysfs mTHP stats.

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Message-Id: <20240816054805.5201-5-kanchana.p.sridhar@intel.com>
Date: Thu, 15 Aug 2024 22:48:05 -0700
From: Kanchana P Sridhar <kanchana.p.sridhar@...el.com>
To: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	hannes@...xchg.org,
	yosryahmed@...gle.com,
	nphamcs@...il.com,
	ryan.roberts@....com,
	ying.huang@...el.com,
	21cnbao@...il.com,
	akpm@...ux-foundation.org
Cc: nanhai.zou@...el.com,
	wajdi.k.feghali@...el.com,
	vinodh.gopal@...el.com,
	kanchana.p.sridhar@...el.com
Subject: [PATCH v2 4/4] mm: swap: Count successful mTHP ZSWAP stores in sysfs mTHP stats.

If zswap_store() successfully stores an mTHP, it will be
counted under the per-order sysfs "zswpout" stats:

/sys/kernel/mm/transparent_hugepage/hugepages-*kB/stats/zswpout

Other block dev/fs mTHP swap-out events will be counted under
the existing sysfs "swpout" stats:

/sys/kernel/mm/transparent_hugepage/hugepages-*kB/stats/swpout

Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@...el.com>
---
 mm/page_io.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/page_io.c b/mm/page_io.c
index ff8c99ee3af7..debd04fbdfd0 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -172,6 +172,12 @@ int generic_swapfile_activate(struct swap_info_struct *sis,
 	goto out;
 }
 
+static inline void count_mthp_zswpout_vm_event(struct folio *folio)
+{
+	if (IS_ENABLED(CONFIG_THP_SWAP))
+		count_mthp_stat(folio_order(folio), MTHP_STAT_ZSWPOUT);
+}
+
 /*
  * We may have stale swap cache pages in memory: notice
  * them here and get rid of the unnecessary final write.
@@ -196,6 +202,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
 		return ret;
 	}
 	if (zswap_store(folio)) {
+		count_mthp_zswpout_vm_event(folio);
 		folio_unlock(folio);
 		return 0;
 	}
-- 
2.27.0