Re: [PATCH 02/11] hisi_sas: alloc queue id of slot according to device id

[John Garry]

On 16/11/2016 01:41, Zhangfei Gao wrote:
> On Mon, Nov 7, 2016 at 8:48 PM, John Garry <john.garry@xxxxxxxxxx> wrote:
> > From: Xiang Chen <chenxiang66@xxxxxxxxxxxxx>
> >
> > Currently slots are allocated from queues in a round-robin fashion.
> > This causes a problem for internal commands in device mode. For this
> > mode, we should ensure that the internal abort command is the last
> > command seen in the host for that device. We can only ensure this when
> > we place the internal abort command after the preceding commands for
> > device that in the same queue, as there is no order in which the host
> > will select a queue to execute the next command.
>
> Is there performance penalty, since only one queue is supported for a device.

Hi Zhangfei,

From testing I have not seen any noteable performance change. However, 
please note the comment on mq, below.

Cheers,
John

> > This queue restriction makes supporting scsi mq more tricky in
> > the future, but should not be a blocker.
> >
> > Note: Even though v1 hw does not support internal abort, the
> >       allocation method is chosen to be the same for consistency.
> >
> > Signed-off-by: Xiang Chen <chenxiang66@xxxxxxxxxxxxx>
> > Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
>
> Reviewed-by: Zhangfei Gao <zhangfei.gao@xxxxxxxxxx>
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