Re: [PATCH] blk-mq: issue directly if hw queue isn't busy in case of 'none'
On 7/9/18 7:03 PM, Ming Lei wrote: > In case of 'none' io scheduler, when hw queue isn't busy, it isn't > necessary to enqueue request to sw queue and dequeue it from > sw queue because request may be submitted to hw queue asap without > extra cost, meantime there shouldn't be much request in sw queue, > and we don't need to worry about effect on IO merge. > > There are still some single hw queue SCSI HBAs(HPSA, megaraid_sas, ...) > which may connect high performance devices, so 'none' is often required > for obtaining good performance. > > This patch improves IOPS and decreases CPU unilization on megaraid_sas, > per Kashyap's test. Looks reasonable to me, applied for 4.19. -- Jens Axboe
RE: [PATCH] blk-mq: issue directly if hw queue isn't busy in case of 'none'
> -Original Message- > From: Ming Lei [mailto:ming@redhat.com] > Sent: Tuesday, July 10, 2018 6:34 AM > To: Jens Axboe > Cc: linux-block@vger.kernel.org; Ming Lei; Kashyap Desai; Laurence Oberman; > Omar Sandoval; Christoph Hellwig; Bart Van Assche; Hannes Reinecke > Subject: [PATCH] blk-mq: issue directly if hw queue isn't busy in case of 'none' > > In case of 'none' io scheduler, when hw queue isn't busy, it isn't > necessary to enqueue request to sw queue and dequeue it from > sw queue because request may be submitted to hw queue asap without > extra cost, meantime there shouldn't be much request in sw queue, > and we don't need to worry about effect on IO merge. > > There are still some single hw queue SCSI HBAs(HPSA, megaraid_sas, ...) > which may connect high performance devices, so 'none' is often required > for obtaining good performance. This Patch is tested on my setup and seeing very good performance improvement. Just use one R0 VD from configuration - Without upstream fix and RHEL7.5 kernel - IOPS goes 840K and CPU utilization goes upto 11%. After applying another block layer fix - IOPS goes 1066K and CPU utilization goes up to 6%. Overall performance improvement is 30% performance and 80% less cpu utilization. Any review comments ? Kashyap > > This patch improves IOPS and decreases CPU unilization on megaraid_sas, > per Kashyap's test. > > Cc: Kashyap Desai > Cc: Laurence Oberman > Cc: Omar Sandoval > Cc: Christoph Hellwig > Cc: Bart Van Assche > Cc: Hannes Reinecke > Reported-by: Kashyap Desai > Tested-by: Kashyap Desai > Signed-off-by: Ming Lei
