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
> >
> >
prev 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 unexpected -ENOMEM from percpu_counter_init() 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]
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