Re: [PATCH 4/5] blk-mq: do limited block plug for multiple queue case

2015-05-04 Thread Jens Axboe
On 05/04/2015 02:33 PM, Shaohua Li wrote: On Mon, May 04, 2015 at 01:46:49PM -0600, Jens Axboe wrote: On 05/04/2015 01:40 PM, Shaohua Li wrote: On Fri, May 01, 2015 at 04:16:04PM -0400, Jeff Moyer wrote: Shaohua Li writes: plug is still helpful for workload with IO merge, but it can be harm

Re: [PATCH 4/5] blk-mq: do limited block plug for multiple queue case

2015-05-04 Thread Shaohua Li
On Mon, May 04, 2015 at 01:46:49PM -0600, Jens Axboe wrote: > On 05/04/2015 01:40 PM, Shaohua Li wrote: > >On Fri, May 01, 2015 at 04:16:04PM -0400, Jeff Moyer wrote: > >>Shaohua Li writes: > >> > >>>plug is still helpful for workload with IO merge, but it can be harmful > >>>otherwise especially

Re: [PATCH 4/5] blk-mq: do limited block plug for multiple queue case

2015-05-04 Thread Jens Axboe
On 05/04/2015 01:40 PM, Shaohua Li wrote: On Fri, May 01, 2015 at 04:16:04PM -0400, Jeff Moyer wrote: Shaohua Li writes: plug is still helpful for workload with IO merge, but it can be harmful otherwise especially with multiple hardware queues, as there is (supposed) no lock contention in thi

Re: [PATCH 4/5] blk-mq: do limited block plug for multiple queue case

2015-05-04 Thread Shaohua Li
On Fri, May 01, 2015 at 04:16:04PM -0400, Jeff Moyer wrote: > Shaohua Li writes: > > > plug is still helpful for workload with IO merge, but it can be harmful > > otherwise especially with multiple hardware queues, as there is > > (supposed) no lock contention in this case and plug can introduce

Re: [PATCH 4/5] blk-mq: do limited block plug for multiple queue case

2015-05-01 Thread Jeff Moyer
Shaohua Li writes: > plug is still helpful for workload with IO merge, but it can be harmful > otherwise especially with multiple hardware queues, as there is > (supposed) no lock contention in this case and plug can introduce > latency. For multiple queues, we do limited plug, eg plug only if th