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Subject: RE: [PATCH 1/2] scsi: ufs: Introduce hba performance monitor sysfs
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Sender: Daejun Park <daejun7.park@samsung.com>
From:   Daejun Park <daejun7.park@samsung.com>
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        "Martin K. Petersen" <martin.petersen@oracle.com>,
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Date:   Tue, 06 Apr 2021 13:11:40 +0900
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References: <1617257704-1154-2-git-send-email-cang@codeaurora.org>
        <1617257704-1154-1-git-send-email-cang@codeaurora.org>
        <CGME20210401061611epcas2p279c9303e0e0bf4e2bc5eb1f4ffd84c52@epcms2p5>
Precedence: bulk

Hi Can Guo,

> +static ssize_t monitor_enable_store(struct device *dev,
> +                                    struct device_attribute *attr,
> +                                    const char *buf, size_t count)
> +{
> +        struct ufs_hba *hba = dev_get_drvdata(dev);
> +        unsigned long value, flags;
> +
> +        if (kstrtoul(buf, 0, &value))
> +                return -EINVAL;
> +
> +        value = !!value;
> +        spin_lock_irqsave(hba->host->host_lock, flags);
> +        if (value == hba->monitor.enabled)
> +                goto out_unlock;
> +
> +        if (!value) {
> +                memset(&hba->monitor, 0, sizeof(hba->monitor));
> +        } else {
> +                hba->monitor.enabled = true;
> +                hba->monitor.enabled_ts = ktime_get();

How about setting lat_max to and lat_min to KTIME_MAX and 0?
I think lat_sum should be 0 at this point.

> +        }
> +
> +out_unlock:
> +        spin_unlock_irqrestore(hba->host->host_lock, flags);
> +        return count;
> +}


> +static void ufshcd_update_monitor(struct ufs_hba *hba, struct ufshcd_lrb *lrbp)
> +{
> +        int dir = ufshcd_monitor_opcode2dir(*lrbp->cmd->cmnd);
> +
> +        if (dir >= 0 && hba->monitor.nr_queued[dir] > 0) {
> +                struct request *req = lrbp->cmd->request;
> +                struct ufs_hba_monitor *m = &hba->monitor;
> +                ktime_t now, inc, lat;
> +
> +                now = ktime_get();

How about using lrbp->compl_time_stamp instead of getting new value?

> +                inc = ktime_sub(now, m->busy_start_ts[dir]);
> +                m->total_busy[dir] = ktime_add(m->total_busy[dir], inc);
> +                m->nr_sec_rw[dir] += blk_rq_sectors(req);
> +
> +                /* Update latencies */
> +                m->nr_req[dir]++;
> +                lat = ktime_sub(now, lrbp->issue_time_stamp);
> +                m->lat_sum[dir] += lat;
> +                if (m->lat_max[dir] < lat || !m->lat_max[dir])
> +                        m->lat_max[dir] = lat;
> +                if (m->lat_min[dir] > lat || !m->lat_min[dir])
> +                        m->lat_min[dir] = lat;

This if statement can be shorted, by setting lat_max / lat_min as default value.

> +
> +                m->nr_queued[dir]--;
> +                /* Push forward the busy start of monitor */
> +                m->busy_start_ts[dir] = now;
> +        }
> +}

Thanks,
Daejun