Re: 2.4.1pre8 slowdown on dbench tests

[Jens Axboe]

On Mon, Jan 22 2001, Marcelo Tosatti wrote:
> 
> Jens, 
> 
> Steven is a seeing a slowdown in his results, too. 
> 
> 
> On Mon, 22 Jan 2001, Steven Cole wrote:
> 
> > On Thursday 18 January 2001 14:49, Marcelo Tosatti wrote:
> > 
> > > Steven,
> > >
> > > The issue is the difference between pre4 and pre8.
> > >
> > > Could you please try pre4 and report results ?
> > >
> > > Thanks
> > 
> > Ok, here are the results for 2.4.1-pre4, along with the original -pre8 
> > results.  There does appear to be a slowdown.
> > 
> > 2.4.1-pre4
> > average:   9.77876 MB/sec
> > 
> > Throughput 10.3677 MB/sec (NB=12.9597 MB/sec  103.677 MBit/sec)
> > Throughput 9.61291 MB/sec (NB=12.0161 MB/sec  96.1291 MBit/sec)
> > Throughput 9.92944 MB/sec (NB=12.4118 MB/sec  99.2944 MBit/sec)
> > Throughput 9.20502 MB/sec (NB=11.5063 MB/sec  92.0502 MBit/sec)
> > 
> > 2.4.1-pre8:
> > Average    9.25707 MB/sec
> > 
> > Throughput 8.93444 MB/sec (NB=11.1681 MB/sec  89.3444 MBit/sec)
> > Throughput 9.43609 MB/sec (NB=11.7951 MB/sec  94.3609 MBit/sec)
> > Throughput 9.5075 MB/sec (NB=11.8844 MB/sec  95.075 MBit/sec)
> > Throughput 9.15026 MB/sec (NB=11.4378 MB/sec  91.5026 MBit/sec)
> > 
> > This was done on a dual P-III, 256MB machine.

Stephen,

To rule out other factors, could you try 2.4.1-pre8 with
blk_started_io() and blk_finished_io() defined to nothing
in include/linux/blkdev.h? This will disable the max-locked-buffers
heuristic.

Also, are the numbers above consistent for repeated runs (with
boots in between)?

-- 
* Jens Axboe <[e-mail]>
* SuSE Labs