linux-kernel - Re: [fuse-devel] Horrible mmap write performance (kernel writeback issue?)

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Message-ID: <CA+icZUVYWoy-RAeujbU7DuC3gQUA1O1qWHFgruA_unfzx32CmA@mail.gmail.com>
Date:	Wed, 13 Apr 2016 09:20:58 +0200
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Ashish Sangwan <ashishsangwan2@...il.com>,
	Jakob Unterwurzacher <jakobunt@...il.com>,
	Miklos Szeredi <miklos@...redi.hu>,
	fuse-devel <fuse-devel@...ts.sourceforge.net>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [fuse-devel] Horrible mmap write performance (kernel writeback issue?)

On Tue, Apr 12, 2016 at 1:09 PM, Tejun Heo <tj@...nel.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@...nel.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@...il.com>

Patch available from [1].

- sed@ -

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