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

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Date:	Tue, 12 Apr 2016 14:54:08 +0530
From:	Ashish Sangwan <ashishsangwan2@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	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 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.

Thanks,
Ashish
>
> Thanks.
>
> --
> tejun