From: Roman Gushchin <guro@fb.com>
To: Andrew Morton <akpm@linux-foundation.org>, <linux-mm@kvack.org>
Cc: =Shakeel Butt <shakeelb@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>, <kernel-team@fb.com>,
<linux-kernel@vger.kernel.org>, Roman Gushchin <guro@fb.com>,
Michal Hocko <mhocko@suse.com>
Subject: [PATCH] mm: workingset: ignore slab memory size when calculating shadows pressure
Date: Thu, 3 Sep 2020 16:00:55 -0700 [thread overview]
Message-ID: <20200903230055.1245058-1-guro@fb.com> (raw)
In the memcg case count_shadow_nodes() sums the number of pages in lru
lists and the amount of slab memory (reclaimable and non-reclaimable)
as a baseline for the allowed number of shadow entries.
It seems to be a good analogy for the !memcg case, where
node_present_pages() is used. However, it's not quite true, as there
two problems:
1) Due to slab reparenting introduced by commit fb2f2b0adb98 ("mm:
memcg/slab: reparent memcg kmem_caches on cgroup removal") local
per-lruvec slab counters might be inaccurate on non-leaf levels.
It's the only place where local slab counters are used.
2) Shadow nodes by themselves are backed by slabs. So there is a loop
dependency: the more shadow entries are there, the less pressure the
kernel applies to reclaim them.
Fortunately, there is a simple way to solve both problems: slab
counters shouldn't be taken into the account by count_shadow_nodes().
Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shakeel Butt <shakeelb@google.com>
---
mm/workingset.c | 4 ----
1 file changed, 4 deletions(-)
diff --git a/mm/workingset.c b/mm/workingset.c
index 92e66113a577..50d53f3699e4 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -495,10 +495,6 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
for (pages = 0, i = 0; i < NR_LRU_LISTS; i++)
pages += lruvec_page_state_local(lruvec,
NR_LRU_BASE + i);
- pages += lruvec_page_state_local(
- lruvec, NR_SLAB_RECLAIMABLE_B) >> PAGE_SHIFT;
- pages += lruvec_page_state_local(
- lruvec, NR_SLAB_UNRECLAIMABLE_B) >> PAGE_SHIFT;
} else
#endif
pages = node_present_pages(sc->nid);
--
2.26.2
next reply other threads:[~2020-09-03 23:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-03 23:00 Roman Gushchin [this message]
2020-09-04 4:10 ` [PATCH] mm: workingset: ignore slab memory size when calculating shadows pressure Andrew Morton
2020-09-04 5:02 ` Roman Gushchin
2020-09-09 14:55 ` Johannes Weiner
2020-09-09 16:55 ` Roman Gushchin
2020-09-10 17:50 ` Johannes Weiner
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