On Fri, Oct 11, 2013 at 08:28:54AM -0600, Jens Axboe wrote: > On 10/11/2013 01:18 AM, Shaohua Li wrote: > > Using percpu-ida to manage blk-mq tags. the percpu-ida has similar algorithm > > like the blk-mq-tag. The difference is when a cpu can't allocate tags > > blk-mq-tag uses ipi to purge remote cpu cache and percpu-ida directly purges > > remote cpu cache. In practice (testing null_blk), the percpu-ida approach is > > much faster when total tags aren't enough. > > I'm not surprised it's a lot faster the the pathological case of needing > to prune tags, the IPI isn't near ideal for that. I'm assuming the > general performance is the same for the non-full case?
Yep. My test is done in a 2 sockets machine, 12 process cross the 2 sockets. So if there is lock contention or ipi, should be stressed heavily. Testing is done for null-blk. hw_queue_depth nopatch iops patch iops 64 ~800k/s ~1470k/s 2048 ~4470k/s ~4340k/s In the 2048 case, perf doesn't should any percpu-ida function is hot (no one use > 1% cpu time), so the small difference should be drift. So yes, the general performance is the same. Thanks, Shaohua -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
