linux-kernel - Re: FUSE: write operations trigger balance_dirty

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Message-ID: <CAJfpegscozvNV3R4h1NZCGLq_Te8AHXEAxymRJNj96OkmPFFJw@mail.gmail.com>
Date:   Thu, 9 Aug 2018 10:30:22 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     刘硕然 <liushuoran@...com>
Cc:     "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: FUSE: write operations trigger balance_dirty_pages when using
 writeback cache

On Thu, Aug 9, 2018 at 9:31 AM, 刘硕然 <liushuoran@...com> wrote:
> Thank you for the prompt reply.
>
> I tried this config, but still can get balance_dirty_pages triggered.

I think it may be due to BDI_CAP_STRICTLIMIT used by fuse.  If you
remove that setting from fuse in the kernel you should not be getting
the balance_dirty_pages() as often.

Not sure if that's the realproblem, though, that depends on how much
time is spent in balance_dirty_pages().  You can try profiling the
kernel to find that out.

My guess is that the real cause of the slowdown is some other place.
There's for example a known issue with selinux related getxattr
thrashing.  Disabling getxattr on your filesystem may significantly
improve performance.

Thanks,
Miklos