linux-kernel - Re: [PATCH V5 00/14] blk-mq-sched: improve sequential I/O performance(part 1)

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Date:   Tue, 10 Oct 2017 13:24:52 +0100
From:   John Garry <john.garry@...wei.com>
To:     Ming Lei <ming.lei@...hat.com>
CC:     Jens Axboe <axboe@...com>, <linux-block@...r.kernel.org>,
        "Christoph Hellwig" <hch@...radead.org>,
        Mike Snitzer <snitzer@...hat.com>, <dm-devel@...hat.com>,
        Bart Van Assche <bart.vanassche@...disk.com>,
        "Laurence Oberman" <loberman@...hat.com>,
        Paolo Valente <paolo.valente@...aro.org>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        Tom Nguyen <tom81094@...il.com>,
        <linux-kernel@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
        Omar Sandoval <osandov@...com>, Linuxarm <linuxarm@...wei.com>
Subject: Re: [PATCH V5 00/14] blk-mq-sched: improve sequential I/O
 performance(part 1)

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

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

Cheers,
John

>
> -- Ming .