Re: Performance degradation with FFSB between 2.6.20 and 2.6.21-rc7

[Jens Axboe <jens.axboe@oracle.com>]

On Wed, Apr 18 2007, Valerie Clement wrote:
> 
> Running benchmark tests (FFSB) on an ext4 filesystem, I noticed a 
> performance degradation (about 15-20 percent) in sequential write tests 
> between 2.6.19-rc6 and 2.6.21-rc4 kernels.
> 
> I ran the same tests on ext3 and XFS filesystems and I saw the same 
> performance difference between the two kernel versions for these two 
> filesystems.
> 
> I have also reproduced it between 2.6.20.7 and 2.6.21-rc7.
> The FFSB tests run 16 threads, each creating 1GB files. The tests were 
> done on the same x86_64 system, with the same kernel configuration and 
> on the same scsi device. Below are the throughput values given by FFSB.
> 
>   kernel           XFS                ext3
> ----------
>  2.6.20.7        48 MB/sec         44 MB/sec
> 
>  2.6.21-rc7      38 MB/sec         37 MB/sec
> 
> Did anyone else run across the problem?
> Is there a known issue?

Please tell me how you are running ffsb, and also please include a
dmessg from a booted system.

-- 
Jens Axboe