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

From: John Garry
Date: Wed Nov 16 2016 - 05:03:27 EST

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.


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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