The patch titled
Subject: mm: memcontrol: try harder to set a new memory.high
has been removed from the -mm tree. Its filename was
mm-memcontrol-try-harder-to-set-a-new-memoryhigh.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: 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@xxxxxxxxxxx
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 30 ++++++++++++++++++++++++------
1 file changed, 24 insertions(+), 6 deletions(-)
--- a/mm/memcontrol.c~mm-memcontrol-try-harder-to-set-a-new-memoryhigh
+++ a/mm/memcontrol.c
@@ -6091,7 +6091,8 @@ static ssize_t memory_high_write(struct
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
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;
}
_
Patches currently in -mm which might be from hannes@xxxxxxxxxxx are
