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

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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

#1365017 — Re: [fuse-devel] Horrible mmap write performance (kernel writeback issue?)

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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#1365649 — Re: [fuse-devel] Horrible mmap write performance (kernel writeback issue?)

On Sat, Mar 26, 2016 at 10:42 PM, Jakob Unterwurzacher
<jakobunt@gmail.com> wrote:
> 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
>

Tejun,

Any idea why this commit stalls fuse mmap writes?

Here's the start of the this thread:

  http://marc.info/?l=fuse-devel&m=145008058603261&w=2

Thanks,
Miklos


> 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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#1367517

Hello,

On Mon, Mar 28, 2016 at 09:45:53PM +0200, Miklos Szeredi wrote:
> >> 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
> >
> 
> Tejun,
> 
> Any idea why this commit stalls fuse mmap writes?
> 
> Here's the start of the this thread:
> 
>   http://marc.info/?l=fuse-devel&m=145008058603261&w=2

Hmmm... cgroup writeback support shouldn't affect fuse at all as the
backing device doesn't enable cgroup support.  I probably made some
silly mistake.  Is there a simple reproducer I can play with?

Thanks.

-- 
tejun

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#1369881 — Re: [fuse-devel] Horrible mmap write performance (kernel writeback issue?)

On Wed, Mar 30, 2016 at 8:47 PM, Tejun Heo <tj@kernel.org> wrote:
> Hello,
>
> On Mon, Mar 28, 2016 at 09:45:53PM +0200, Miklos Szeredi wrote:
>> >> 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
>> >
>>
>> Tejun,
>>
>> Any idea why this commit stalls fuse mmap writes?
>>
>> Here's the start of the this thread:
>>
>>   http://marc.info/?l=fuse-devel&m=145008058603261&w=2
>
> Hmmm... cgroup writeback support shouldn't affect fuse at all as the
> backing device doesn't enable cgroup support.  I probably made some
> silly mistake.  Is there a simple reproducer I can play with?
>
> Thanks.
>

To quote Jakob from a previous email:

"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."

Hope this helps.

- Sedat -

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