Re: sysbench+mysql(oltp, readonly) 30% regression with 2.6.26-rc1

[Peter Zijlstra]

On Thu, 2008-05-08 at 11:15 +0200, Mike Galbraith wrote:
> On Thu, 2008-05-08 at 17:01 +0800, Zhang, Yanmin wrote:
> > On Thu, 2008-05-08 at 10:00 +0200, Mike Galbraith wrote:
> 
> > > Hm.  I was doing some sysbench+postgress(oltp, ro) testing on my little
> > > Q6600 box this morning, and saw a different picture.
> 
> > How many cpu are in the Q6600?
> 
> 1.
> 
> > > 
> > > In attached pdf, .bkl refers to Linus' BKL patch, .weight is the weight
> > > fix, both are applied to git.today.  The script I used is also attached.
> > With my 8-core stoakley (using mysql):
> > 1) 2.6.25:
> > Number of threads: 6
> >     read/write requests:                 8025024 (66874.53 per sec.)
> > Number of threads: 8
> >     read/write requests:                 9132816 (76106.14 per sec.)
> > Number of threads: 10
> >     read/write requests:                 9244998 (77040.75 per sec.)
> > Number of threads: 12
> >     read/write requests:                 8994174 (74950.36 per sec.)
> > Number of threads: 14
> >     read/write requests:                 9051322 (75426.54 per sec.)
> > Number of threads: 16
> >     read/write requests:                 9015412 (75126.93 per sec.)
> > 
> > 2) 2.6.26-rc1:
> > Number of threads: 6
> >     read/write requests:                 5754056 (47949.87 per sec.)
> > Number of threads: 8
> >     read/write requests:                 6528480 (54403.29 per sec.)
> > Number of threads: 10
> >     read/write requests:                 6444690 (53705.16 per sec.)
> > Number of threads: 12
> >     read/write requests:                 6544258 (54534.23 per sec.)
> > Number of threads: 14
> >     read/write requests:                 6796650 (56637.65 per sec.)
> > Number of threads: 16
> >     read/write requests:                 6718110 (55983.18 per sec.)
> > 
> > 3) 2.6.26-rc1+weight
> > ïNumber of threads: 16
> > 	read/write requests:                 3219076 (26824.22 per sec.)
> > 
> > I'm not sure if more cpu could introduce more contention in this test.
> 
> -rc1.  Do you have the fix below applied?

Oooh - good catch, that seems to be a post -rc1 merge.

Yes this is required.

> commit a992241de614dd2b7c97a9ba64e28c0e563f19bf
> Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Date:   Mon May 5 23:56:17 2008 +0200
> 
>     sched: fix normalized sleeper
>     
>     Normalized sleeper uses calc_delta*() which requires that the rq load is
>     already updated, so move account_entity_enqueue() before place_entity()
>     
>     Tested-by: Frans Pop <elendil@xxxxxxxxx>
>     Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
>     Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
> 
> diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
> index 89fa32b..1295ddc 100644
> --- a/kernel/sched_fair.c
> +++ b/kernel/sched_fair.c
> @@ -682,6 +682,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
>  	 * Update run-time statistics of the 'current'.
>  	 */
>  	update_curr(cfs_rq);
> +	account_entity_enqueue(cfs_rq, se);
>  
>  	if (wakeup) {
>  		place_entity(cfs_rq, se, 0);
> @@ -692,7 +693,6 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
>  	check_spread(cfs_rq, se);
>  	if (se != cfs_rq->curr)
>  		__enqueue_entity(cfs_rq, se);
> -	account_entity_enqueue(cfs_rq, se);
>  }
>  
>  static void update_avg(u64 *avg, u64 sample)
> 
> 

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