From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, Johannes Weiner <hannes@cmpxchg.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/2] oom, memcg: do not report racy no-eligible OOM
Date: Sat, 12 Jan 2019 19:52:50 +0900 [thread overview]
Message-ID: <0aacad13-3e91-646a-90b1-c70993b05701@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20190111164536.GJ14956@dhcp22.suse.cz>
On 2019/01/12 1:45, Michal Hocko wrote:
>>> Anyway, could you update your patch and abstract
>>> if (unlikely(tsk_is_oom_victim(current) ||
>>> fatal_signal_pending(current) ||
>>> current->flags & PF_EXITING))
>>>
>>> in try_charge and reuse it in mem_cgroup_out_of_memory under the
>>> oom_lock with an explanation please?
>>
>> I don't think doing so makes sense, for
>>
>> tsk_is_oom_victim(current) = T && fatal_signal_pending(current) == F
>>
>> can't happen for mem_cgroup_out_of_memory() under the oom_lock, and
>> current->flags cannot get PF_EXITING when current is inside
>> mem_cgroup_out_of_memory(). fatal_signal_pending(current) alone is
>> appropriate for mem_cgroup_out_of_memory() under the oom_lock because
>>
>> tsk_is_oom_victim(current) = F && fatal_signal_pending(current) == T
>>
>> can happen there.
>
> I meant to use the same check consistently. If we can bypass the charge
> under a list of conditions in the charge path we should be surely be
> able to the the same for the oom path. I will not insist but unless
> there is a strong reason I would prefer that.
>
You mean something like this? I'm not sure this change is safe.
mm/memcontrol.c | 27 +++++++++++++++++++++++----
1 file changed, 23 insertions(+), 4 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 17189da..1733d019 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -248,6 +248,12 @@ enum res_type {
iter != NULL; \
iter = mem_cgroup_iter(NULL, iter, NULL))
+static inline bool can_ignore_limit(void)
+{
+ return tsk_is_oom_victim(current) || fatal_signal_pending(current) ||
+ (current->flags & PF_EXITING);
+}
+
/* Some nice accessors for the vmpressure. */
struct vmpressure *memcg_to_vmpressure(struct mem_cgroup *memcg)
{
@@ -1395,7 +1401,7 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
* A few threads which were not waiting at mutex_lock_killable() can
* fail to bail out. Therefore, check again after holding oom_lock.
*/
- ret = fatal_signal_pending(current) || out_of_memory(&oc);
+ ret = can_ignore_limit() || out_of_memory(&oc);
mutex_unlock(&oom_lock);
return ret;
}
@@ -1724,6 +1730,10 @@ static enum oom_status mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int
mem_cgroup_unmark_under_oom(memcg);
if (mem_cgroup_out_of_memory(memcg, mask, order))
+ /*
+ * Returning OOM_SUCCESS upon can_ignore_limit() is OK, for
+ * the caller will check can_ignore_limit() again.
+ */
ret = OOM_SUCCESS;
else
ret = OOM_FAILED;
@@ -1783,6 +1793,11 @@ bool mem_cgroup_oom_synchronize(bool handle)
finish_wait(&memcg_oom_waitq, &owait.wait);
mem_cgroup_out_of_memory(memcg, current->memcg_oom_gfp_mask,
current->memcg_oom_order);
+ /*
+ * Returning upon can_ignore_limit() is OK, for the caller is
+ * already killed... CheckMe: Is this assumption correct?
+ * Page fault can't happen after getting PF_EXITING?
+ */
} else {
schedule();
mem_cgroup_unmark_under_oom(memcg);
@@ -2215,9 +2230,7 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
* bypass the last charges so that they can exit quickly and
* free their memory.
*/
- if (unlikely(tsk_is_oom_victim(current) ||
- fatal_signal_pending(current) ||
- current->flags & PF_EXITING))
+ if (unlikely(can_ignore_limit()))
goto force;
/*
@@ -5527,6 +5540,12 @@ static ssize_t memory_max_write(struct kernfs_open_file *of,
memcg_memory_event(memcg, MEMCG_OOM);
if (!mem_cgroup_out_of_memory(memcg, GFP_KERNEL, 0))
break;
+ /*
+ * There is no need to check can_ignore_limit() here, for
+ * signal_pending(current) above will break anyway.
+ */
+ if (unlikely(can_ignore_limit()))
+ break;
}
memcg_wb_domain_size_changed(memcg);
--
1.8.3.1
next prev parent reply other threads:[~2019-01-12 10:53 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-07 14:38 [PATCH 0/2] oom, memcg: do not report racy no-eligible OOM Michal Hocko
2019-01-07 14:38 ` [PATCH 1/2] mm, oom: marks all killed tasks as oom victims Michal Hocko
2019-01-07 20:58 ` Tetsuo Handa
2019-01-08 8:11 ` Michal Hocko
2019-01-07 14:38 ` [PATCH 2/2] memcg: do not report racy no-eligible OOM tasks Michal Hocko
2019-01-07 20:59 ` Tetsuo Handa
2019-01-08 8:14 ` Michal Hocko
2019-01-08 10:39 ` Tetsuo Handa
2019-01-08 11:46 ` Michal Hocko
2019-01-08 8:35 ` kbuild test robot
2019-01-08 9:39 ` Michal Hocko
2019-01-11 0:23 ` [kbuild-all] " Rong Chen
2019-01-08 14:21 ` [PATCH 3/2] memcg: Facilitate termination of memcg OOM victims Tetsuo Handa
2019-01-08 14:38 ` Michal Hocko
2019-01-09 11:03 ` [PATCH 0/2] oom, memcg: do not report racy no-eligible OOM Michal Hocko
2019-01-09 11:34 ` Tetsuo Handa
2019-01-09 12:02 ` Michal Hocko
2019-01-10 23:59 ` Tetsuo Handa
2019-01-11 10:25 ` Tetsuo Handa
2019-01-11 11:33 ` Michal Hocko
2019-01-11 12:40 ` Tetsuo Handa
2019-01-11 13:34 ` Michal Hocko
2019-01-11 14:31 ` Tetsuo Handa
2019-01-11 15:07 ` Michal Hocko
2019-01-11 15:37 ` Tetsuo Handa
2019-01-11 16:45 ` Michal Hocko
2019-01-12 10:52 ` Tetsuo Handa [this message]
2019-01-13 17:36 ` 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=0aacad13-3e91-646a-90b1-c70993b05701@i-love.sakura.ne.jp \
--to=penguin-kernel@i-love.sakura.ne.jp \
--cc=akpm@linux-foundation.org \
--cc=hannes@cmpxchg.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
/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).