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

From	Jakob Unterwurzacher <jakobunt@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [fuse-devel] Horrible mmap write performance (kernel writeback issue?)
Date	2016-03-26 22:50 +0100
Message-ID	<rh4fM-6NC-3@gated-at.bofh.it> (permalink)
References	<rdgfw-7bg-13@gated-at.bofh.it> <rdgfw-7bg-15@gated-at.bofh.it> <rdgfw-7bg-17@gated-at.bofh.it> <rdgfw-7bg-11@gated-at.bofh.it>
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On 16.03.2016 10:44, Miklos Szeredi wrote:
> On Tue, Mar 15, 2016 at 8:55 AM, Jakob Unterwurzacher
> <jakobunt@gmail.com> wrote:
>> Just for anybody finding this thread: This still happens in v4.4, it
>> just took longer to trigger.
>>
>> I have posted more details to linux-kernel (copy-pasted below),
>> http://thread.gmane.org/gmane.linux.kernel/2132944
> 
> Okay, so you can reproduce this relatively quickly.   Can you try "git
> bisect" to find exactly which commit is responsible?
> 
> Thanks,
> Miklos

That took a while, but it looks like it got it:

> commit 947e9762a8ddefda38aa21e249e6a4fec215cd12
> Author: Tejun Heo <tj@kernel.org>
> Date:   Fri May 22 18:23:32 2015 -0400
> 
>     writeback: update wb_over_bg_thresh() to use wb_domain aware operations

Note that this commens seems to only activate changes that happened in the
commit before, aa661bb:

> commit aa661bbe1e61ce80ca4ae98804f673ede94b0827
> Author: Tejun Heo <tj@kernel.org>
> Date:   Fri May 22 18:23:31 2015 -0400
> 
>     writeback: move over_bground_thresh() to mm/page-writeback.c


Anyway, I can reliably reboot between aa661bb and 947e976 and always get the
same results:

aa661bb passes
947e976 fails

I you want to reproduce, clone https://github.com/rfjakob/mmapwrite.git and
run ./encfs-test.sh (needs encfs installed). On the bad kernel, it will hang
within a few seconds.

Thanks,
Jakob

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Re: [fuse-devel] Horrible mmap write performance (kernel writeback  issue?) Jakob Unterwurzacher <jakobunt@gmail.com> - 2016-03-26 22:50 +0100
  Re: [fuse-devel] Horrible mmap write performance (kernel writeback issue?) Miklos Szeredi <miklos@szeredi.hu> - 2016-03-28 21:50 +0200
    Re: [fuse-devel] Horrible mmap write performance (kernel writeback  issue?) Tejun Heo <tj@kernel.org> - 2016-03-30 20:50 +0200
      Re: [fuse-devel] Horrible mmap write performance (kernel writeback issue?) Sedat Dilek <sedat.dilek@gmail.com> - 2016-04-02 08:40 +0200

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