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

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Message-ID: <20160412002428.GQ24661@htj.duckdns.org>
Date:	Mon, 11 Apr 2016 20:24:28 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Jakob Unterwurzacher <jakobunt@...il.com>
Cc:	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?)

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.

Thanks.

-- 
tejun