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Date: Wed, 13 Apr 2016 09:20:58 +0200
Message-ID: <CA+icZUVYWoy-RAeujbU7DuC3gQUA1O1qWHFgruA_unfzx32CmA@mail.gmail.com>
Subject: Re: [fuse-devel] Horrible mmap write performance (kernel writeback issue?)
From: Sedat Dilek <sedat.dilek@gmail.com>
To: Tejun Heo <tj@kernel.org>
Cc: Ashish Sangwan <ashishsangwan2@gmail.com>,
        Jakob Unterwurzacher <jakobunt@gmail.com>,
        Miklos Szeredi <miklos@szeredi.hu>,
        fuse-devel <fuse-devel@lists.sourceforge.net>,
        Linux-Fsdevel <linux-fsdevel@vger.kernel.org>,
        Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Tue, Apr 12, 2016 at 1:09 PM, Tejun Heo <tj@kernel.org> wrote:
> Hello,
>
> On Tue, Apr 12, 2016 at 02:54:08PM +0530, Ashish Sangwan wrote:
>> On Tue, Apr 12, 2016 at 5:54 AM, Tejun Heo <tj@kernel.org> wrote:
>> > Hello,
>> >
>> > On Mon, Apr 11, 2016 at 10:04:42AM +0200, Jakob Unterwurzacher wrote:
>> >> What seems to be happening in the kernel is that the estimated device bandwith
>> >> drops to zero. I'm not even sure how this works for FUSE, but that's what I
>> >> gathered from some printk debugging.
>> >
>> > Yeah, writeback bw getting messed up is the most likely cause.  Prolly
>> > some silly bug.  I can reproduce the problem.  Looking into it.
>>
>> Probably you want to look into:
>> https://lkml.org/lkml/2016/3/10/21
>>
>> The patch mentioned above solves the issue for me.
>
> Heh, I tracked it down to wb_over_bg_thresh() and fell asleep.  Yeah,
> that is the right fix.
>

Feel free to add my...

     Tested-by: Sedat Dilek <sedat.dilek@gmail.com>

Patch available from [1].

- sed@ -

[1] https://patchwork.kernel.org/patch/8554181/