Re: Updated performance results

[Chris Mason <chris.mason@oracle.com>]

On Fri, Sep 11, 2009 at 04:35:50PM -0500, Steven Pratt wrote:
> Chris Mason wrote:
> >On Mon, Aug 31, 2009 at 12:49:13PM -0500, Steven Pratt wrote:
> >>Better late than never. Finally got this finished up.  Mixed bag on
> >>this one.  BTRFS lags significantly on single threaded.  Seems
> >>unable to keep IO outstanding to the device.  Less that 60% busy on
> >>the DM device, compared to 97%+ for all other filesystems.
> >>nodatacow helps out, increasing utilization to about 70%, but still
> >>trails by a large margin.
> >
> >Hi Steve,
> >
> >Jens Axboe did some profiling on his big test rig and I think we found
> >the biggest CPU problems.  The end result is now setting in the master
> >branch of the btrfs-unstable repo.
> >
> >On his boxes, btrfs went from around 400MB/s streaming writes to 1GB/s
> >limit, and we're now tied with XFS while using less CPU time.
> >
> >Hopefully you will see similar results ;)
> Hmmm, well no I didn't.  Throughputs at 1 and 128 threads are pretty
> much unchanged, although I do see a good CPU savings on the 128
> thread case (with cow).  For 16 threads we actually regressed with
> cow enabled.
> 
> Results  are here:
> 
> http://btrfs.boxacle.net/repository/raid/large_create_test/write-test/1M_odirect_create.html
> 
> I'll try to look more into this next week.
> 

Hmmm, Jens was benchmarking buffered writes, but he was also testing on
his new per-bdi write back code.  If your next run could be buffered
instead of O_DIRECT, I'd be curious to see the results.

Thanks,
Chris