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authorJohannes Weiner <hannes@cmpxchg.org>2019-11-30 17:50:09 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-12-01 06:29:18 -0800
commit8c8c383c04f6cbcda38e38b2430cb245da4d7e5a (patch)
treef67ddec92369719a8b2f38e06084988ccb59af65 /mm/memcontrol.c
parent7249c9f01da30ae5cd1843a54a8fab9b35dd979d (diff)
mm: memcontrol: try harder to set a new memory.high
Setting a memory.high limit below the usage makes almost no effort to shrink the cgroup to the new target size. While memory.high is a "soft" limit that isn't supposed to cause OOM situations, we should still try harder to meet a user request through persistent reclaim. For example, after setting a 10M memory.high on an 800M cgroup full of file cache, the usage shrinks to about 350M: + cat /cgroup/workingset/memory.current 841568256 + echo 10M + cat /cgroup/workingset/memory.current 355729408 This isn't exactly what the user would expect to happen. Setting the value a few more times eventually whittles the usage down to what we are asking for: + echo 10M + cat /cgroup/workingset/memory.current 104181760 + echo 10M + cat /cgroup/workingset/memory.current 31801344 + echo 10M + cat /cgroup/workingset/memory.current 10440704 To improve this, add reclaim retry loops to the memory.high write() callback, similar to what we do for memory.max, to make a reasonable effort that the usage meets the requested size after the call returns. Afterwards, a single write() to memory.high is enough in all but extreme cases: + cat /cgroup/workingset/memory.current 841609216 + echo 10M + cat /cgroup/workingset/memory.current 10182656 790M is not a reasonable reclaim target to ask of a single reclaim invocation. And it wouldn't be reasonable to optimize the reclaim code for it. So asking for the full size but retrying is not a bad choice here: we express our intent, and benefit if reclaim becomes better at handling larger requests, but we also acknowledge that some of the deltas we can encounter in memory_high_write() are just too ridiculously big for a single reclaim invocation to manage. Link: http://lkml.kernel.org/r/20191022201518.341216-2-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c30
1 files changed, 24 insertions, 6 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2bd6d470c5f1..94a5b6d831f9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6091,7 +6091,8 @@ static ssize_t memory_high_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
- unsigned long nr_pages;
+ unsigned int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
+ bool drained = false;
unsigned long high;
int err;
@@ -6102,12 +6103,29 @@ static ssize_t memory_high_write(struct kernfs_open_file *of,
memcg->high = high;
- nr_pages = page_counter_read(&memcg->memory);
- if (nr_pages > high)
- try_to_free_mem_cgroup_pages(memcg, nr_pages - high,
- GFP_KERNEL, true);
+ for (;;) {
+ unsigned long nr_pages = page_counter_read(&memcg->memory);
+ unsigned long reclaimed;
+
+ if (nr_pages <= high)
+ break;
+
+ if (signal_pending(current))
+ break;
+
+ if (!drained) {
+ drain_all_stock(memcg);
+ drained = true;
+ continue;
+ }
+
+ reclaimed = try_to_free_mem_cgroup_pages(memcg, nr_pages - high,
+ GFP_KERNEL, true);
+
+ if (!reclaimed && !nr_retries--)
+ break;
+ }
- memcg_wb_domain_size_changed(memcg);
return nbytes;
}