On Wed, 2018-02-28 at 23:21 +0800, Ming Lei wrote: > On Wed, Feb 28, 2018 at 08:28:48PM +0530, Kashyap Desai wrote: > > Ming - > > > > Quick testing on my setup - Performance slightly degraded (4-5% > > drop)for > > megaraid_sas driver with this patch. (From 1610K IOPS it goes to > > 1544K) > > I confirm that after applying this patch, we have #queue = #numa > > node. > > > > ls -l > > /sys/devices/pci0000:80/0000:80:02.0/0000:83:00.0/host10/target10:2 > > :23/10: > > 2:23:0/block/sdy/mq > > total 0 > > drwxr-xr-x. 18 root root 0 Feb 28 09:53 0 > > drwxr-xr-x. 18 root root 0 Feb 28 09:53 1 > > OK, thanks for your test. > > As I mentioned to you, this patch should have improved performance on > megaraid_sas, but the current slight degrade might be caused by > scsi_host_queue_ready() in scsi_queue_rq(), I guess. > > With .host_tagset enabled and use per-numa-node hw queue, request can > be > queued to lld more frequently/quick than single queue, then the cost > of > atomic_inc_return(&host->host_busy) may be increased much meantime, > think about millions of such operations, and finally slight IOPS drop > is observed when the hw queue depth becomes half of .can_queue. > > > > > > > I would suggest to skip megaraid_sas driver changes using > > shared_tagset > > until and unless there is obvious gain. If overall interface of > > using > > shared_tagset is commit in kernel tree, we will investigate > > (megaraid_sas > > driver) in future about real benefit of using it. > > I'd suggest to not merge it until it is proved that performance can > be > improved in real device. > > I will try to work to remove the expensive atomic_inc_return(&host- > >host_busy) > from scsi_queue_rq(), since it isn't needed for SCSI_MQ, once it is > done, will > ask you to test again. > > > Thanks, > Ming I will test this here as well I just put the Megaraid card in to my system here Kashyap, do you have ssd's on the back-end and are you you using jbods or virtual devices. Let me have your config. I only have 6G sas shelves though. Regards Laurence
