[linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch

[Lee Revell]

On Sat, 2004-07-24 at 01:46, Lee Revell wrote:
> On Sat, 2004-07-24 at 00:07, Lee Revell wrote:
> > On Tue, 2004-07-20 at 08:19, Jens Axboe wrote:
> > > On Tue, Jul 20 2004, Ingo Molnar wrote:
> > > > > How much I/O do you allow to be in flight at once?  It seems like by
> > > > > decreasing the maximum size of I/O that you handle in one interrupt
> > > > > you could improve this quite a bit.  Disk throughput is good enough,
> > > > > anyone in the real world who would feel a 10% hit would just throw
> > > > > hardware at the problem.
> > > > 
> > > it's not tweakable right now, but if you wish to experiment you just
> > > need to add a line to ide-disk.c:idedisk_setup() - pseudo patch:
> > > 
> > > +	blk_queue_max_sectors(drive->queue, 32);
> > > +
> > I am currently testing the effect on throughput and will have some
> > better numbers soon.
> 
> OK, here are my bonnie test results.  They are not what I expected -
> read and write performance is significantly better with 16KB max request
> size, while seeking is much better with 1024KB.
> 

I repeated the test with 'bonnie -f' and without jackd running, and with
32KB vs. 1024KB.  The results are not as drastic, which suggests that
all the overhead from the XRUN tracing was a factor.

These results show that 32KB is better than 1024KB in some areas, and
not singificantly worse in any of these metrics.

32KB:

Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
mindpipe         1G           38499  68 16383  28           35913  34 154.5   1
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16   257  99 +++++ +++ 24008  98   256  99 +++++ +++  1179  98
mindpipe,1G,,,38499,68,16383,28,,,35913,34,154.5,1,16,257,99,+++++,+++,24008,98,256,99,+++++,+++,1179,98

1024KB:

Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
mindpipe         1G           38285  60 13961  20           33694  28 155.2   1
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16   259  99 +++++ +++ 24250  98   256  99 +++++ +++  1184  98
mindpipe,1G,,,38285,60,13961,20,,,33694,28,155.2,1,16,259,99,+++++,+++,24250,98,256,99,+++++,+++,1184,98

Lee