+ zswap-export-more-zswap-store-failure-stats.patch added to mm-unstable branch

+ zswap-export-more-zswap-store-failure-stats.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: zswap: export more zswap store failure stats
has been added to the -mm mm-unstable branch.  Its filename is
     zswap-export-more-zswap-store-failure-stats.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zswap-export-more-zswap-store-failure-stats.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: Nhat Pham <nphamcs@gmail.com>
Subject: zswap: export more zswap store failure stats
Date: Mon, 23 Oct 2023 17:07:02 -0700

Since commit 42c06a0e8ebe ("mm: kill frontswap") we no longer have a
counter to tracks the number of zswap store failures.  This makes it hard
to investigate and monitor for zswap issues.

This patch adds a global and a per-cgroup zswap store failure counter,
as well as a dedicated debugfs counter for compression algorithm failure
(which can happen for e.g when random data are passed to zswap).

Link: https://lkml.kernel.org/r/20231024000702.1387130-1-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/vm_event_item.h |    1 +
 mm/memcontrol.c               |    1 +
 mm/vmstat.c                   |    1 +
 mm/zswap.c                    |   18 ++++++++++++++----
 4 files changed, 17 insertions(+), 4 deletions(-)

--- a/include/linux/vm_event_item.h~zswap-export-more-zswap-store-failure-stats
+++ a/include/linux/vm_event_item.h
@@ -145,6 +145,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PS
 #ifdef CONFIG_ZSWAP
 		ZSWPIN,
 		ZSWPOUT,
+		ZSWPOUT_FAIL,
 #endif
 #ifdef CONFIG_X86
 		DIRECT_MAP_LEVEL2_SPLIT,
--- a/mm/memcontrol.c~zswap-export-more-zswap-store-failure-stats
+++ a/mm/memcontrol.c
@@ -593,6 +593,7 @@ static const unsigned int memcg_vm_event
 #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)
 	ZSWPIN,
 	ZSWPOUT,
+	ZSWPOUT_FAIL,
 #endif
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	THP_FAULT_ALLOC,
--- a/mm/vmstat.c~zswap-export-more-zswap-store-failure-stats
+++ a/mm/vmstat.c
@@ -1401,6 +1401,7 @@ const char * const vmstat_text[] = {
 #ifdef CONFIG_ZSWAP
 	"zswpin",
 	"zswpout",
+	"zswpout_fail",
 #endif
 #ifdef CONFIG_X86
 	"direct_map_level2_splits",
--- a/mm/zswap.c~zswap-export-more-zswap-store-failure-stats
+++ a/mm/zswap.c
@@ -62,6 +62,8 @@ static u64 zswap_pool_limit_hit;
 static u64 zswap_written_back_pages;
 /* Store failed due to a reclaim failure after pool limit was reached */
 static u64 zswap_reject_reclaim_fail;
+/* Store failed due to compression algorithm failure */
+static u64 zswap_reject_compress_fail;
 /* Compressed page was too big for the allocator to (optimally) store */
 static u64 zswap_reject_compress_poor;
 /* Store failed because underlying allocator could not get memory */
@@ -1221,10 +1223,10 @@ bool zswap_store(struct folio *folio)
 
 	/* Large folios aren't supported */
 	if (folio_test_large(folio))
-		return false;
+		goto out_reject;
 
 	if (!zswap_enabled || !tree)
-		return false;
+		goto out_reject;
 
 	/*
 	 * If this is a duplicate, it must be removed before attempting to store
@@ -1317,8 +1319,10 @@ bool zswap_store(struct folio *folio)
 	ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait);
 	dlen = acomp_ctx->req->dlen;
 
-	if (ret)
+	if (ret) {
+		zswap_reject_compress_fail++;
 		goto put_dstmem;
+	}
 
 	/* store */
 	zpool = zswap_find_zpool(entry);
@@ -1385,8 +1389,12 @@ put_dstmem:
 freepage:
 	zswap_entry_cache_free(entry);
 reject:
-	if (objcg)
+	if (objcg) {
+		count_objcg_event(objcg, ZSWPOUT_FAIL);
 		obj_cgroup_put(objcg);
+	}
+out_reject:
+	count_vm_event(ZSWPOUT_FAIL);
 	return false;
 
 shrink:
@@ -1558,6 +1566,8 @@ static int zswap_debugfs_init(void)
 			   zswap_debugfs_root, &zswap_reject_alloc_fail);
 	debugfs_create_u64("reject_kmemcache_fail", 0444,
 			   zswap_debugfs_root, &zswap_reject_kmemcache_fail);
+	debugfs_create_u64("reject_compress_fail", 0444,
+			   zswap_debugfs_root, &zswap_reject_compress_fail);
 	debugfs_create_u64("reject_compress_poor", 0444,
 			   zswap_debugfs_root, &zswap_reject_compress_poor);
 	debugfs_create_u64("written_back_pages", 0444,
_

Patches currently in -mm which might be from nphamcs@gmail.com are

zswap-export-more-zswap-store-failure-stats.patch