On Sat, Jun 06, 2009 at 02:23:40AM +0200, Jan Kara wrote: > On Fri 05-06-09 20:18:15, Chris Mason wrote: > > On Fri, Jun 05, 2009 at 11:14:38PM +0200, Jan Kara wrote: > > > On Fri 05-06-09 21:15:28, Jens Axboe wrote: > > > > On Fri, Jun 05 2009, Frederic Weisbecker wrote: > > > > > The result with noop is even more impressive. > > > > > > > > > > See: http://kernel.org/pub/linux/kernel/people/frederic/dbench-noop.pdf > > > > > > > > > > Also a comparison, noop with pdflush against noop with bdi writeback: > > > > > > > > > > http://kernel.org/pub/linux/kernel/people/frederic/dbench-noop-cmp.pdf > > > > > > > > OK, so things aren't exactly peachy here to begin with. It may not > > > > actually BE an issue, or at least now a new one, but that doesn't mean > > > > that we should not attempt to quantify the impact. > > > What looks interesting is also the overall throughput. With pdflush we > > > get to 2.5 MB/s + 26 MB/s while with per-bdi we get to 2.7 MB/s + 13 MB/s. > > > So per-bdi seems to be *more* fair but throughput suffers a lot (which > > > might be inevitable due to incurred seeks). > > > Frederic, how much does dbench achieve for you just on one partition > > > (test both consecutively if possible) with as many threads as have those > > > two dbench instances together? Thanks. > > > > Is the graph showing us dbench tput or disk tput? I'm assuming it is > > disk tput, so bdi may just be writing less? > Good, question. I was assuming dbench throughput :). > > Honza Yeah it's dbench. May be that's not the right tool to measure the writeback layer, even though dbench results are necessarily influenced by the writeback behaviour. May be I should use something else? Note that if you want I can put some surgicals trace_printk() in fs/fs-writeback.c > > -- > Jan Kara <jack@xxxxxxx> > SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
