On Tue, Oct 10, 2017 at 01:24:52PM +0100, John Garry wrote:

On 10/10/2017 02:46, Ming Lei wrote:

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I tested this series for the SAS controller on HiSilicon hip07 platform as I
am interested in enabling MQ for this driver. Driver is
./drivers/scsi/hisi_sas/.

So I found that that performance is improved when enabling default SCSI_MQ
with this series vs baseline. However, it is still not as a good as when
default SCSI_MQ is disabled.

Here are some figures I got with fio:
4.14-rc2 without default SCSI_MQ
read, rw, write IOPS	
952K, 133K/133K, 800K

4.14-rc2 with default SCSI_MQ
read, rw, write IOPS	
311K, 117K/117K, 320K

This series* without default SCSI_MQ
read, rw, write IOPS	
975K, 132K/132K, 790K

This series* with default SCSI_MQ
read, rw, write IOPS	
770K, 164K/164K, 594K

Thanks for testing this patchset!

Looks there is big improvement, but the gap compared with
block legacy is not small too.

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Please note that hisi_sas driver does not enable mq by exposing multiple
queues to upper layer (even though it has multiple queues). I have been
playing with enabling it, but my performance is always worse...

* I'm using
https://github.com/ming1/linux/commits/blk_mq_improve_scsi_mpath_perf_V5.1,
as advised by Ming Lei.

Could you test on the following branch and see if it makes a
difference?

	https://github.com/ming1/linux/commits/blk_mq_improve_scsi_mpath_perf_V6.1_test

Hi John,

Please test the following branch directly:

https://github.com/ming1/linux/tree/blk_mq_improve_scsi_mpath_perf_V6.2_test

And code is simplified and cleaned up much in V6.2, then only two extra
patches(top 2) are needed against V6 which was posted yesterday.

Please test SCSI_MQ with mq-deadline, which should be the default
mq scheduler on your HiSilicon SAS.

Hi Ming Lei,

It's using cfq (for non-mq) and mq-deadline (obviously for mq).

root@(none)$ pwd
/sys/devices/platform/HISI0162:01/host0/port-0:0/expander-0:0/port-0:0:7/end_device-0:0:7
root@(none)$ more ./target0:0:3/0:0:3:0/block/sdd/queue/scheduler
noop [cfq]

and

root@(none)$ more ./target0:0:3/0:0:3:0/block/sdd/queue/scheduler
[mq-deadline] kyber none

Unfortunately my setup has changed since yeterday, and the absolute figures
are not the exact same (I retested 4.14-rc2). However, we still see that
drop when mq is enabled.

Here's the results:
4.14-rc4 without default SCSI_MQ
read, rw, write IOPS	
860K, 112K/112K, 800K

4.14-rc2 without default SCSI_MQ
read, rw, write IOPS	
880K, 113K/113K, 808K

V6.2 series without default SCSI_MQ
read, rw, write IOPS	
820K, 114/114K, 790K

Hi John,

All change in V6.2 is blk-mq/scsi-mq only, which shouldn't
affect non SCSI_MQ, so I suggest you to compare the perf
between deadline and mq-deadline, like Johannes mentioned.

V6.2 series with default SCSI_MQ
read, rw, write IOPS	
700K, 130K/128K, 640K

If possible, could you provide your fio script and log on both
non SCSI_MQ(deadline) and SCSI_MQ(mq_deadline)? Maybe some clues
can be figured out.

Also, I just put another patch on V6.2 branch, which may improve
a bit too. You may try that in your test.

	https://github.com/ming1/linux/commit/e31e2eec46c9b5ae7cfa181e9b77adad2c6a97ce

-- 
Ming