linux-kernel - Re: [performance bug] kernel building regression on 64 LCPUs machine

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Message-ID: <x497hch2p8q.fsf@segfault.boston.devel.redhat.com>
Date:	Wed, 02 Mar 2011 16:20:53 -0500
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Jan Kara <jack@...e.cz>
Cc:	Corrado Zoccolo <czoccolo@...il.com>,
	"Alex\,Shi" <alex.shi@...el.com>,
	"Li\, Shaohua" <shaohua.li@...el.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	"tytso\@mit.edu" <tytso@....edu>,
	"jaxboe\@fusionio.com" <jaxboe@...ionio.com>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	"Chen\, Tim C" <tim.c.chen@...el.com>
Subject: Re: [performance bug] kernel building regression on 64 LCPUs machine

Jan Kara <jack@...e.cz> writes:

> On Wed 02-03-11 11:13:53, Jeff Moyer wrote:
>> Jan Kara <jack@...e.cz> writes:
>> > On Tue 01-03-11 14:56:43, Jeff Moyer wrote:
>> >> Corrado Zoccolo <czoccolo@...il.com> writes:
>> >> 
>> >> > On Thu, Feb 24, 2011 at 1:13 PM, Jan Kara <jack@...e.cz> wrote:
>> >> >> On Wed 23-02-11 16:24:47, Alex,Shi wrote:
>> >> >>> Though these patches can not totally recovered the problem, but they are
>> >> >>> quite helpful with ccache enabled situation. It increase 10% performance
>> >> >>> on 38-rc1 kernel.
>> >> >>  OK and what was the original performance drop with WRITE_SYNC change?
>> >> >>
>> >> >>> I have tried to enabled they to latest rc6 kernel but failed. the vmstat output is here:
>> >> >>> with patches:
>> >> >>  I'm attaching patches rebased on top of latest Linus's tree.
>> >> >> Corrado, could you possibly run your fsync-heavy tests so that we see
>> >> >> whether there isn't negative impact of my patches on your fsync-heavy
>> >> >> workload? Thanks.
>> >> > The workload was actually Jeff's, and the stalls that my change tried
>> >> > to mitigate showed up on his enterprise class storage. Adding him so
>> >> > he can test it.
>> >> 
>> >> Sorry for the late reply.  You can use either fs_mark or iozone to
>> >> generate an fsync-heavy workload.  The test I did was to mix this with a
>> >> sequential reader.  If you can point me at patches, I should be able to
>> >> test this.
>> >   The latest version of patches is attached to:
>> > https://lkml.org/lkml/2011/2/24/125
>> 
>> Perhaps you should fix up the merge conflicts, first?  ;-)
>> 
>> +<<<<<<< HEAD
>>         tid = transaction->t_tid;
>>         need_to_start = !tid_geq(journal->j_commit_request, tid);
>> +=======
>> +       __jbd2_log_start_commit(journal, transaction->t_tid, false);
>> +>>>>>>> jbd2: Refine commit writeout logic
>   Doh, how embarrassing ;). Attached is a new version which compiles and
> seems to run OK.
>
> 								Honza

Thanks, Jan.  I should have results for you tomorrow.

Cheers,
Jeff
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