From: Michal Hocko <mhocko@suse.com>
To: Vasily Averin <vvs@virtuozzo.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH memcg] memcg: prohibit unconditional exceeding the limit of dying tasks
Date: Mon, 13 Sep 2021 12:55:21 +0200 [thread overview]
Message-ID: <YT8uGUMQ7K+/0gyA@dhcp22.suse.cz> (raw)
In-Reply-To: <7af26106-388c-6f99-e018-669a8f0cf9b5@virtuozzo.com>
On Mon 13-09-21 13:35:00, Vasily Averin wrote:
> On 9/13/21 11:53 AM, Michal Hocko wrote:
> > On Fri 10-09-21 15:39:28, Vasily Averin wrote:
> >> The kernel currently allows dying tasks to exceed the memcg limits.
> >> The allocation is expected to be the last one and the occupied memory
> >> will be freed soon.
> >> This is not always true because it can be part of the huge vmalloc
> >> allocation. Allowed once, they will repeat over and over again.
> >> Moreover lifetime of the allocated object can differ from
> >> In addition the lifetime of the dying task.
> >> Multiple such allocations running concurrently can not only overuse
> >> the memcg limit, but can lead to a global out of memory and,
> >> in the worst case, cause the host to panic.
> >>
> >> Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
> >> ---
> >> mm/memcontrol.c | 23 +++++------------------
> >> 1 file changed, 5 insertions(+), 18 deletions(-)
> >>
> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> >> index 389b5766e74f..67195fcfbddf 100644
> >> --- a/mm/memcontrol.c
> >> +++ b/mm/memcontrol.c
> >> @@ -1834,6 +1834,9 @@ static enum oom_status mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int
> >> return OOM_ASYNC;
> >> }
> >>
> >> + if (should_force_charge())
> >> + return OOM_SKIPPED;
> >
> > mem_cgroup_out_of_memory already check for the bypass, now you are
> > duplicating that check with a different answer to the caller. This is
> > really messy. One of the two has to go away.
>
> In this case mem_cgroup_out_of_memory() takes locks and mutexes but doing nothing
> useful and its success causes try_charge_memcg() to repeat the loop unnecessarily.
>
> I cannot change mem_cgroup_out_of_memory internals, because it is used in other places too.The check inside mem_cgroup_out_of_memory is required because situation can be changed after
> check added into mem_cgroup_oom().
>
> Though I got your argument, and will think how to improve the patch.
> Anyway we'll need to do something with name of should_force_charge() function
> that will NOT lead to forced charge.
Here is what I would do.
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 702a81dfe72d..58269721d438 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2588,6 +2588,7 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
struct page_counter *counter;
enum oom_status oom_status;
unsigned long nr_reclaimed;
+ bool passed_oom = false;
bool may_swap = true;
bool drained = false;
unsigned long pflags;
@@ -2622,15 +2623,6 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
if (gfp_mask & __GFP_ATOMIC)
goto force;
- /*
- * Unlike in global OOM situations, memcg is not in a physical
- * memory shortage. Allow dying and OOM-killed tasks to
- * bypass the last charges so that they can exit quickly and
- * free their memory.
- */
- if (unlikely(should_force_charge()))
- goto force;
-
/*
* Prevent unbounded recursion when reclaim operations need to
* allocate memory. This might exceed the limits temporarily,
@@ -2688,8 +2680,9 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
if (gfp_mask & __GFP_RETRY_MAYFAIL)
goto nomem;
- if (fatal_signal_pending(current))
- goto force;
+ /* Avoid endless loop for tasks bypassed by the oom killer */
+ if (passed_oom && should_force_charge())
+ goto nomem;
/*
* keep retrying as long as the memcg oom killer is able to make
@@ -2698,14 +2691,10 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
*/
oom_status = mem_cgroup_oom(mem_over_limit, gfp_mask,
get_order(nr_pages * PAGE_SIZE));
- switch (oom_status) {
- case OOM_SUCCESS:
+ if (oom_status == OOM_SUCCESS) {
+ passed_oom = true;
nr_retries = MAX_RECLAIM_RETRIES;
goto retry;
- case OOM_FAILED:
- goto force;
- default:
- goto nomem;
}
nomem:
if (!(gfp_mask & __GFP_NOFAIL))
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-09-13 10:55 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-10 12:39 [PATCH memcg] memcg: prohibit unconditional exceeding the limit of dying tasks Vasily Averin
2021-09-10 13:04 ` Tetsuo Handa
2021-09-10 13:20 ` Vasily Averin
2021-09-10 14:55 ` Michal Hocko
2021-09-13 8:29 ` Vasily Averin
2021-09-13 8:42 ` Michal Hocko
2021-09-17 8:06 ` [PATCH mm] vmalloc: back off when the current task is OOM-killed Vasily Averin
2021-09-19 23:31 ` Andrew Morton
2021-09-20 1:22 ` Tetsuo Handa
2021-09-20 10:59 ` Vasily Averin
2021-09-21 18:55 ` Andrew Morton
2021-09-22 6:18 ` Vasily Averin
2021-09-22 12:27 ` Michal Hocko
2021-09-23 6:49 ` Vasily Averin
2021-09-24 7:55 ` Michal Hocko
2021-09-27 9:36 ` Vasily Averin
2021-09-27 11:08 ` Michal Hocko
2021-10-05 13:52 ` [PATCH mm v2] " Vasily Averin
2021-10-05 14:00 ` Vasily Averin
2021-10-07 10:47 ` Michal Hocko
2021-10-07 19:55 ` Andrew Morton
2021-09-10 13:07 ` [PATCH memcg] memcg: prohibit unconditional exceeding the limit of dying tasks Vasily Averin
2021-09-13 7:51 ` Vasily Averin
2021-09-13 8:39 ` Michal Hocko
2021-09-13 9:37 ` Vasily Averin
2021-09-13 10:10 ` Michal Hocko
2021-09-13 8:53 ` Michal Hocko
2021-09-13 10:35 ` Vasily Averin
2021-09-13 10:55 ` Michal Hocko [this message]
2021-09-14 10:01 ` Vasily Averin
2021-09-14 10:10 ` [PATCH memcg v2] " Vasily Averin
2021-09-16 12:55 ` Michal Hocko
2021-10-05 13:52 ` [PATCH memcg v3] " Vasily Averin
2021-10-05 14:55 ` Michal Hocko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YT8uGUMQ7K+/0gyA@dhcp22.suse.cz \
--to=mhocko@suse.com \
--cc=akpm@linux-foundation.org \
--cc=cgroups@vger.kernel.org \
--cc=hannes@cmpxchg.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=penguin-kernel@i-love.sakura.ne.jp \
--cc=vdavydov.dev@gmail.com \
--cc=vvs@virtuozzo.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).