Re: [PATCH V3 8/8] scsi: megaraid: improve scsi_mq performance via .host_tagset

Ming Lei
2018-03-07T05:27:31Z

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
>
>
> 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.

Hi Kashyap,

Now I have put patches for removing operating on scsi_host->host_busy
in V4[1], especially which are done in the following 3 patches:

9221638b9bc9 scsi: avoid to hold host_busy for scsi_mq
1ffc8c0ffbe4 scsi: read host_busy via scsi_host_busy()
e453d3983243 scsi: introduce scsi_host_busy()

Could you run your test on V4 and see if IOPS can be improved on
megaraid_sas?

[1] https://github.com/ming1/linux/commits/v4.16-rc-host-tags-v4

Thanks,
Ming