RE: [PATCH] storvsc: setup 1:1 mapping between hardware queue and CPU queue

[Long Li]

>>>Subject: Re: [PATCH] storvsc: setup 1:1 mapping between hardware queue
>>>and CPU queue
>>>
>>>On Tue, Aug 20, 2019 at 3:36 AM <longli@xxxxxxxxxxxxxxxxx> wrote:
>>>>
>>>> From: Long Li <longli@xxxxxxxxxxxxx>
>>>>
>>>> storvsc doesn't use a dedicated hardware queue for a given CPU queue.
>>>> When issuing I/O, it selects returning CPU (hardware queue)
>>>> dynamically based on vmbus channel usage across all channels.
>>>>
>>>> This patch sets up a 1:1 mapping between hardware queue and CPU
>>>queue,
>>>> thus avoiding unnecessary locking at upper layer when issuing I/O.
>>>>
>>>> Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
>>>> ---
>>>>  drivers/scsi/storvsc_drv.c | 16 ++++++++++++++--
>>>>  1 file changed, 14 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
>>>> index b89269120a2d..26c16d40ec46 100644
>>>> --- a/drivers/scsi/storvsc_drv.c
>>>> +++ b/drivers/scsi/storvsc_drv.c
>>>> @@ -1682,6 +1682,18 @@ static int storvsc_queuecommand(struct
>>>Scsi_Host *host, struct scsi_cmnd *scmnd)
>>>>         return 0;
>>>>  }
>>>>
>>>> +static int storvsc_map_queues(struct Scsi_Host *shost) {
>>>> +       unsigned int cpu;
>>>> +       struct blk_mq_queue_map *qmap =
>>>> +&shost->tag_set.map[HCTX_TYPE_DEFAULT];
>>>> +
>>>> +       for_each_possible_cpu(cpu) {
>>>> +               qmap->mq_map[cpu] = cpu;
>>>> +       }
>>>
>>>Block layer provides the helper of blk_mq_map_queues(), so suggest you
>>>to use the default cpu mapping, instead of inventing a new one.

Thanks for the pointer. I'm sending a v2.

Long

>>>
>>>thanks,
>>>Ming Lei