lkml.org 
[lkml]   [2009]   [Apr]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: tiobench read 50% regression with 2.6.30-rc1
From
Date
On Tue, 2009-04-14 at 14:14 +0200, Jens Axboe wrote:
> On Fri, Apr 10 2009, Zhang, Yanmin wrote:
> > On Thu, 2009-04-09 at 11:57 +0200, Jens Axboe wrote:
> > > On Thu, Apr 09 2009, Zhang, Yanmin wrote:
> > > > Comparing with 2.6.29's result, tiobench (read) has about 50% regression
> > > > with 2.6.30-rc1 on all my machines. Bisect down to below patch.
> > > >
> > > > b029195dda0129b427c6e579a3bb3ae752da3a93 is first bad commit
> > > > commit b029195dda0129b427c6e579a3bb3ae752da3a93
> > > > Author: Jens Axboe <jens.axboe@oracle.com>
> > > > Date: Tue Apr 7 11:38:31 2009 +0200

> > >
> > > It's not a huge surprise that we regressed there. I'll get this fixed up
> > > next week. Can you I talk you into trying to change the 'quantum' sysfs
> > > variable for the drive? It's in /sys/block/xxx/queue/iosched where xxx
> > > is your drive(s). It's set to 4, if you could try progressively larger
> > > settings and retest, that would help get things started.
> > I tried 4,8,16,64,128 and didn't find result difference.
>
> Can you try with this patch?
The new patch does fix it.


>
> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
> index a4809de..66f00e5 100644
> --- a/block/cfq-iosched.c
> +++ b/block/cfq-iosched.c
> @@ -1905,10 +1905,17 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
> * Remember that we saw a request from this process, but
> * don't start queuing just yet. Otherwise we risk seeing lots
> * of tiny requests, because we disrupt the normal plugging
> - * and merging.
> + * and merging. If the request is already larger than a single
> + * page, let it rip immediately. For that case we assume that
> + * merging is already done.
> */
> - if (cfq_cfqq_wait_request(cfqq))
> + if (cfq_cfqq_wait_request(cfqq)) {
> + if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE) {
> + del_timer(&cfqd->idle_slice_timer);
> + blk_start_queueing(cfqd->queue);
> + }
> cfq_mark_cfqq_must_dispatch(cfqq);
> + }
> } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
> /*
> * not the active queue - expire current slice if it is
>



\
 
 \ /
  Last update: 2009-04-15 03:31    [W:0.113 / U:0.116 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site