The patch titled
Subject: mm: memcontrol: try harder to set a new memory.high
has been added to the -mm tree. Its filename is
mm-memcontrol-try-harder-to-set-a-new-memoryhigh.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-memcontrol-try-harder-to-set-a-new-memoryhigh.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-memcontrol-try-harder-to-set-a-new-memoryhigh.patch
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 and is updated
there every 3-4 working days
------------------------------------------------------
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
Link: http://lkml.kernel.org/r/20191022201518.341216-2-hannes@xxxxxxxxxxx
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: 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
@@ -6074,7 +6074,8 @@ 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;
@@ -6085,12 +6086,29 @@ 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
mm-memcontrol-remove-dead-code-from-memory_max_write.patch
mm-memcontrol-try-harder-to-set-a-new-memoryhigh.patch
mm-drop-mmap_sem-before-calling-balance_dirty_pages-in-write-fault.patch
