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
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------------------------------------------------------
From: Nhat Pham <nphamcs@xxxxxxxxx>
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@xxxxxxxxx
Signed-off-by: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Dan Streetman <ddstreet@xxxxxxxx>
Cc: Domenico Cerasuolo <cerasuolodomenico@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Seth Jennings <sjenning@xxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Vitaly Wool <vitaly.wool@xxxxxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxxxx are
zswap-export-more-zswap-store-failure-stats.patch
