Re: [PATCH v2 19/20] scsi: ufs: Implement polling support

Bean Huo
2021-11-30T08:43:50Z

Bart,

We look forward to the support of UFSHCD polling, I did a review and
test. comments as below:

On Fri, 2021-11-19 at 11:57 -0800, Bart Van Assche wrote:
> The time spent in io_schedule() and also the interrupt latency are
> significant when submitting direct I/O to a UFS device. Hence this
> patch
> that implements polling support. User space software can enable
> polling by
> passing the RWF_HIPRI flag to the preadv2() system call or the
> IORING_SETUP_IOPOLL flag to the io_uring interface.
>
> Although the block layer supports to partition the tag space for
> interrupt-based completions (HCTX_TYPE_DEFAULT) purposes and polling
> (HCTX_TYPE_POLL), the choice has been made to use the same hardware
> queue for both hctx types because partitioning the tag space would
> negatively affect performance.
>
> On my test setup this patch increases IOPS from 2736 to 22000 (8x)
> for the
> following test:
>
> for hipri in 0 1; do
> fio --ioengine=io_uring --iodepth=1 --rw=randread \
> --runtime=60 --time_based=1 --direct=1 --name=qd1 \
> --filename=/dev/block/sda --ioscheduler=none --gtod_reduce=1 \
> --norandommap --hipri=$hipri
> done

For 4KB random read, direct IO, and iodepth=1, we did not see an
improvement in IOPS due to this patch. Maybe the test case above is not
sufficient.

>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
> drivers/scsi/ufs/ufshcd.c | 85 ++++++++++++++++++++++++++++++-------
> --
> 1 file changed, 65 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 9cf4a22f1950..14043d74389d 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -2629,6 +2629,36 @@ static inline bool is_device_wlun(struct
> scsi_device *sdev)
> ufshcd_upiu_wlun_to_scsi_wlun(UFS_UPIU_UFS_DEVICE_WLUN)
> ;
> }
>
> +/*
> + * Associate the UFS controller queue with the default and poll HCTX
> types.
> + * Initialize the mq_map[] arrays.
> + */
> +static int ufshcd_map_queues(struct Scsi_Host *shost)
> +{
> + int i, ret;
> +
> + for (i = 0; i < shost->nr_maps; i++) {
> + struct blk_mq_queue_map *map = &shost->tag_set.map[i];
> +
> + switch (i) {
> + case HCTX_TYPE_DEFAULT:
> + case HCTX_TYPE_POLL:
> + map->nr_queues = 1;
> + break;
> + case HCTX_TYPE_READ:
> + map->nr_queues = 0;
> + break;
> + default:
> + WARN_ON_ONCE(true);
> + }
> + map->queue_offset = 0;
> + ret = blk_mq_map_queues(map);
> + WARN_ON_ONCE(ret);
> + }
> +
> + return 0;
> +}
> +
> static void ufshcd_init_lrb(struct ufs_hba *hba, struct ufshcd_lrb
> *lrb, int i)
> {
> struct utp_transfer_cmd_desc *cmd_descp = hba->ucdl_base_addr;
> @@ -2664,7 +2694,7 @@ static int ufshcd_queuecommand(struct Scsi_Host
> *host, struct scsi_cmnd *cmd)
> struct ufshcd_lrb *lrbp;
> int err = 0;
>
> - WARN_ONCE(tag < 0, "Invalid tag %d\n", tag);
> + WARN_ONCE(tag < 0 || tag >= hba->nutrs, "Invalid tag %d\n",
> tag);
>
> /*
> * Allows the UFS error handler to wait for prior
> ufshcd_queuecommand()
> @@ -2925,7 +2955,7 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba
> *hba,
> }
> req = scsi_cmd_to_rq(scmd);
> tag = req->tag;
> - WARN_ONCE(tag < 0, "Invalid tag %d\n", tag);
> + WARN_ONCE(tag < 0 || tag >= hba->nutrs, "Invalid tag %d\n",
> tag)
probably this change should not in this patch?

> /*
> * Start the request such that blk_mq_tag_idle() is called when
> the
> * device management request finishes.
> @@ -5272,6 +5302,31 @@ static void __ufshcd_transfer_req_compl(struct
> ufs_hba *hba,
> }
> }
>
> +/*
> + * Returns > 0 if one or more commands have been completed or 0 if
> no
> + * requests have been completed.
> + */
> +static int ufshcd_poll(struct Scsi_Host *shost, unsigned int
> queue_num)
> +{
> + struct ufs_hba *hba = shost_priv(shost);
> + unsigned long completed_reqs, flags;
> + u32 tr_doorbell;
> +
> + spin_lock_irqsave(&hba->outstanding_lock, flags);
> + tr_doorbell = ufshcd_readl(hba,
> REG_UTP_TRANSFER_REQ_DOOR_BELL);
> + completed_reqs = ~tr_doorbell & hba->outstanding_reqs;
> + WARN_ONCE(completed_reqs & ~hba->outstanding_reqs,
> + "completed: %#lx; outstanding: %#lx\n",
> completed_reqs,
> + hba->outstanding_reqs);
> + hba->outstanding_reqs &= ~completed_reqs;
> + spin_unlock_irqrestore(&hba->outstanding_lock, flags);
> +
> + if (completed_reqs)
> + __ufshcd_transfer_req_compl(hba, completed_reqs);
> +
> + return completed_reqs;
> +}
> +
> /**
> * ufshcd_transfer_req_compl - handle SCSI and query command
> completion
> * @hba: per adapter instance
> @@ -5282,9 +5337,6 @@ static void __ufshcd_transfer_req_compl(struct
> ufs_hba *hba,
> */
> static irqreturn_t ufshcd_transfer_req_compl(struct ufs_hba *hba)
> {
> - unsigned long completed_reqs, flags;
> - u32 tr_doorbell;
> -
> /* Resetting interrupt aggregation counters first and reading
> the
> * DOOR_BELL afterward allows us to handle all the completed
> requests.
> * In order to prevent other interrupts starvation the DB is
> read once
> @@ -5299,21 +5351,9 @@ static irqreturn_t
> ufshcd_transfer_req_compl(struct ufs_hba *hba)
> if (ufs_fail_completion())
> return IRQ_HANDLED;
>
> - spin_lock_irqsave(&hba->outstanding_lock, flags);
> - tr_doorbell = ufshcd_readl(hba,
> REG_UTP_TRANSFER_REQ_DOOR_BELL);
> - completed_reqs = ~tr_doorbell & hba->outstanding_reqs;
> - WARN_ONCE(completed_reqs & ~hba->outstanding_reqs,
> - "completed: %#lx; outstanding: %#lx\n",
> completed_reqs,
> - hba->outstanding_reqs);
> - hba->outstanding_reqs &= ~completed_reqs;
> - spin_unlock_irqrestore(&hba->outstanding_lock, flags);
> + ufshcd_poll(hba->host, 0);
>
> - if (completed_reqs) {
> - __ufshcd_transfer_req_compl(hba, completed_reqs);
> - return IRQ_HANDLED;
> - } else {
> - return IRQ_NONE;
> - }
> + return IRQ_HANDLED;
> }
>

ufshcd_transfer_req_compl() will never return IRQ_NONE,
but ufshcd_intr() needs this return to check the fake interrupt.

> int __ufshcd_write_ee_control(struct ufs_hba *hba, u32 ee_ctrl_mask)
> @@ -6564,6 +6604,8 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba
> *hba,
> spin_lock_irqsave(host->host_lock, flags);
>
> task_tag = req->tag;
> + WARN_ONCE(task_tag < 0 || task_tag >= hba->nutmrs, "Invalid tag
> %d\n",
> + task_tag);
> hba->tmf_rqs[req->tag] = req;
> treq->upiu_req.req_header.dword_0 |= cpu_to_be32(task_tag);
>
> @@ -6705,7 +6747,7 @@ static int ufshcd_issue_devman_upiu_cmd(struct
> ufs_hba *hba,
> }
> req = scsi_cmd_to_rq(scmd);
> tag = req->tag;
> - WARN_ONCE(tag < 0, "Invalid tag %d\n", tag);
> + WARN_ONCE(tag < 0 || tag >= hba->nutrs, "Invalid tag %d\n",
> tag);
> /*
> * Start the request such that blk_mq_tag_idle() is called when
> the
> * device management request finishes.
> @@ -8147,7 +8189,9 @@ static struct scsi_host_template
> ufshcd_driver_template = {
> .module = THIS_MODULE,
> .name = UFSHCD,
> .proc_name = UFSHCD,
> + .map_queues = ufshcd_map_queues,
> .queuecommand = ufshcd_queuecommand,
> + .mq_poll = ufshcd_poll,
> .slave_alloc = ufshcd_slave_alloc,
> .slave_configure = ufshcd_slave_configure,
> .slave_destroy = ufshcd_slave_destroy,
> @@ -9437,6 +9481,7 @@ int ufshcd_alloc_host(struct device *dev,
> struct ufs_hba **hba_handle)
> err = -ENOMEM;
> goto out_error;
> }
> + host->nr_maps = 3;

I don't understand why not directly uses HCTX_MAX_TYPES, 3 is already
maximum.

> hba = shost_priv(host);
> hba->host = host;
> hba->dev = dev;