linux-mm.kvack.org archive mirror
 help / color / mirror / Atom feed
From: Wang Yugui <wangyugui@e16-tech.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, linux-btrfs@vger.kernel.org
Subject: Re: unexpected -ENOMEM from percpu_counter_init()
Date: Fri, 09 Apr 2021 17:52:43 +0800	[thread overview]
Message-ID: <20210409175242.C545.409509F4@e16-tech.com> (raw)
In-Reply-To: <60e9b994-e37c-d059-4af5-0cb7860ca4f3@suse.cz>

Hi, Dennis Zhou, Vlastimil Babka, Filipe Manana

The root reason of this problem maybe the design of
'memalloc_nofs_restore()/memalloc_nofs_save()'.

When some job such as memory pre-alloc and reclaim is needed,  that is
done in a workqueue now.

This is a problem for high-load and over-load. In that case, we need to
do these job in current task/process, so that current task/process will
be blocked until necessary job is done.

If we let these job in done in a workqueue, and current task/process is
not blocked, that means failure is very near, and then we can not work
stable in high-load and over-load.

For high-load and over-load, failure is not expected,  we expect some
job be blocked well.

> > Percpu does do this via a workqueue item. The issue is in v5.9 we
> > introduced 2 types of chunks. However, the free float page number was
> > for the total. So even if 1 chunk type dropped below, the other chunk
> > type might have enough pages. I'm queuing this for 5.12 and will send it
> > out assuming it does fix your problem.

Best Regards
Wang Yugui (wangyugui@e16-tech.com)
2021/04/09

> +CC btrfs
> 
> On 4/1/21 12:51 PM, Wang Yugui wrote:
> > Hi,
> > 
> > an unexpected -ENOMEM from percpu_counter_init() happened when xfstest 
> > with kernel 5.11.10 and 5.10.27
> 
> Is there a dmesg log showing allocation failure or something?
> 
> > direct caller:
> > int btrfs_drew_lock_init(struct btrfs_drew_lock *lock)
> > {
> >     int ret;
> > 
> >     ret = percpu_counter_init(&lock->writers, 0, GFP_KERNEL);
> >     if (ret)
> >         return ret;
> > 
> >     atomic_set(&lock->readers, 0);
> >     init_waitqueue_head(&lock->pending_readers);
> >     init_waitqueue_head(&lock->pending_writers);
> > 
> >     return 0;
> > }
> > 
> > upper caller:
> >     nofs_flag = memalloc_nofs_save();
> >     ret = btrfs_drew_lock_init(&root->snapshot_lock);
> >     memalloc_nofs_restore(nofs_flag);
> >     if (ret == -ENOMEM) printk("ENOMEM btrfs_drew_lock_init\n");
> >     if (ret)
> >         goto fail;
> > 
> > The hardware of this server:
> > CPU:  Xeon(R) CPU E5-2660 v2(10 core)  *2
> > memory:  192G, no swap
> > 
> > Only one xfstests job is running in this server, and about 7% of memory
> > is used.
> > 
> > Any advice please.
> > 
> > Best Regards
> > Wang Yugui (wangyugui@e16-tech.com)
> > 2021/04/01
> > 
> > 




      parent reply	other threads:[~2021-04-09  9:52 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-01 10:51 Wang Yugui
2021-04-02  1:49 ` Wang Yugui
2021-04-07 12:35 ` Vlastimil Babka
2021-04-07 13:09   ` Wang Yugui
2021-04-07 14:56     ` Dennis Zhou
2021-04-07 23:28       ` Wang Yugui
2021-04-08  2:44         ` Dennis Zhou
2021-04-08  9:20           ` Wang Yugui
2021-04-08 13:48             ` Dennis Zhou
2021-04-08 14:28               ` Filipe Manana
2021-04-08 15:02                 ` Dennis Zhou
2021-04-09 11:39                   ` Filipe Manana
2021-04-09 13:39                     ` Dennis Zhou
2021-04-09 13:42                       ` Filipe Manana
2021-04-09  0:08               ` Wang Yugui
2021-04-09  2:14                 ` Dennis Zhou
2021-04-09  4:02                   ` Wang Yugui
2021-04-09  7:36                     ` Wang Yugui
2021-04-09  7:48                       ` Wang Yugui
2021-04-09 13:56                       ` Dennis Zhou
2021-04-10 15:29                         ` Wang Yugui
2021-04-10 15:52                           ` Dennis Zhou
2021-04-10 16:08                             ` Wang Yugui
2021-04-11 15:20                               ` Wang Yugui
2021-04-12  4:03                                 ` Dennis Zhou
2021-04-12  5:24                                   ` Wang Yugui
2021-04-09  9:52   ` Wang Yugui [this message]

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=20210409175242.C545.409509F4@e16-tech.com \
    --to=wangyugui@e16-tech.com \
    --cc=linux-btrfs@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=vbabka@suse.cz \
    --subject='Re: unexpected -ENOMEM from percpu_counter_init()' \
    /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

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox