On 2012-09-07 15:55, Jens Axboe wrote: > On 2012-09-07 14:58, Kent Overstreet wrote: >> On Thu, Sep 06, 2012 at 07:34:18PM -0600, Jens Axboe wrote: >>> On 2012-09-06 16:34, Kent Overstreet wrote: >>>> Reusing bios is something that's been highly frowned upon in the past, >>>> but driver code keeps doing it anyways. If it's going to happen anyways, >>>> we should provide a generic method. >>>> >>>> This'll help with getting rid of bi_destructor - drivers/block/pktcdvd.c >>>> was open coding it, by doing a bio_init() and resetting bi_destructor. >>>> >>>> This required reordering struct bio, but the block layer is not yet >>>> nearly fast enough for any cacheline effects to matter here. >>> >>> That's an odd and misplaced comment. Was just doing testing today at 5M >>> IOPS, and even years back we've had cache effects for O_DIRECT in higher >>> speed setups. >> >> Ah, I wasn't aware that you were pushing that many iops through the >> block layer - most I've tested myself was around 1M. It wouldn't >> surprise me if cache effects in struct bio mattered around 5M... > > 5M is nothing, just did 13.5M :-) > > But we can reshuffle for now. As mentioned, we're way overdue for a > decent look at cache profiling in any case. No ill effects seen so far, fwiw: read : io=1735.8GB, bw=53690MB/s, iops=13745K, runt= 33104msec -- Jens Axboe -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
