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

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Date:	Wed, 2 Mar 2011 22:17:48 +0100
From:	Jan Kara <jack@...e.cz>
To:	Jeff Moyer <jmoyer@...hat.com>
Cc:	Jan Kara <jack@...e.cz>, Corrado Zoccolo <czoccolo@...il.com>,
	"Alex,Shi" <alex.shi@...el.com>,
	"Li, Shaohua" <shaohua.li@...el.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	"tytso@....edu" <tytso@....edu>,
	"jaxboe@...ionio.com" <jaxboe@...ionio.com>,
	"linux-kernel@...r.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

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
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR

View attachment "0001-jbd2-Refine-commit-writeout-logic.patch" of type "text/x-patch" (10820 bytes)

View attachment "0002-jbd-Refine-commit-writeout-logic.patch" of type "text/x-patch" (9844 bytes)