Re: [PATCH v5 2/3] scsi: core: Support disabling fair tag sharing

Yu Kuai
2023-11-15T07:24:41Z

Hi,

在 2023/11/15 2:04, Bart Van Assche 写道:
> Allow SCSI drivers to disable the block layer fair tag sharing algorithm.
>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Martin K. Petersen <martin.petersen@oracle.com>
> Cc: Ming Lei <ming.lei@redhat.com>
> Cc: Keith Busch <kbusch@kernel.org>
> Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com>
> Cc: Yu Kuai <yukuai1@huaweicloud.com>
> Cc: Ed Tsai <ed.tsai@mediatek.com>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
> drivers/scsi/hosts.c | 1 +
> drivers/scsi/scsi_lib.c | 2 ++
> include/scsi/scsi_host.h | 6 ++++++
> 3 files changed, 9 insertions(+)
>
> diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
> index d7f51b84f3c7..872f87001374 100644
> --- a/drivers/scsi/hosts.c
> +++ b/drivers/scsi/hosts.c
> @@ -442,6 +442,7 @@ struct Scsi_Host *scsi_host_alloc(const struct scsi_host_template *sht, int priv
> shost->no_write_same = sht->no_write_same;
> shost->host_tagset = sht->host_tagset;
> shost->queuecommand_may_block = sht->queuecommand_may_block;
> + shost->disable_fair_tag_sharing = sht->disable_fair_tag_sharing;

Can we also consider to disable fair tag sharing by default for the
driver that total driver tags is less than a threshold?

Thanks,
Kuai

>
> if (shost_eh_deadline == -1 || !sht->eh_host_reset_handler)
> shost->eh_deadline = -1;
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index cf3864f72093..291fbfacf542 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1984,6 +1984,8 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
> BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);
> if (shost->queuecommand_may_block)
> tag_set->flags |= BLK_MQ_F_BLOCKING;
> + if (shost->disable_fair_tag_sharing)
> + tag_set->flags |= BLK_MQ_F_DISABLE_FAIR_TAG_SHARING;
> tag_set->driver_data = shost;
> if (shost->host_tagset)
> tag_set->flags |= BLK_MQ_F_TAG_HCTX_SHARED;
> diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
> index 3b907fc2ef08..04238ae9e22c 100644
> --- a/include/scsi/scsi_host.h
> +++ b/include/scsi/scsi_host.h
> @@ -464,6 +464,9 @@ struct scsi_host_template {
> /* The queuecommand callback may block. See also BLK_MQ_F_BLOCKING. */
> unsigned queuecommand_may_block:1;
>
> + /* See also BLK_MQ_F_DISABLE_FAIR_TAG_SHARING. */
> + unsigned disable_fair_tag_sharing:1;
> +
> /*
> * Countdown for host blocking with no commands outstanding.
> */
> @@ -662,6 +665,9 @@ struct Scsi_Host {
> /* The queuecommand callback may block. See also BLK_MQ_F_BLOCKING. */
> unsigned queuecommand_may_block:1;
>
> + /* See also BLK_MQ_F_DISABLE_FAIR_TAG_SHARING. */
> + unsigned disable_fair_tag_sharing:1;
> +
> /* Host responded with short (<36 bytes) INQUIRY result */
> unsigned short_inquiry:1;
>
>
>
> .
>