Hi Can Guo,
>
>Hi Daejun,
>
>On 2021-04-06 12:11, Daejun Park wrote:
>> 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?
>
>lat_min is already 0. What is the benefit of setting lat_max to
>KTIME_MAX?
>
>> I think lat_sum should be 0 at this point.
>
>lat_sum is already 0 at this point, what is the problem?
Sorry. I misunderstood about resetting monitor values.
>
>>
>>> + }
>>> +
>>> +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?
>
>I am expecting "now" keeps increasing and use it to update
>m->busy_start_s,
>but if I use lrbp->compl_time_stamp to do that, below line ktime_sub()
>may
>give me an unexpected value as lrbp->compl_time_stamp may be smaller
>than
>m->busy_start_ts, because the actual requests are not completed by the
>device
>in the exact same ordering as the bits set in hba->outstanding_tasks,
>but driver
>is completing them from bit 0 to bit 31 in ascending order.
lrbp->compl_time_stamp is set just before calling ufshcd_update_monitor().
And I don't think it can be negative value, because ufshcd_send_command()
and __ufshcd_transfer_req_compl() are protected by host lock.
>
>>
>>> + 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.
>
>I don't quite get it, can you show me the code sample?
I think " || !m->lat_max[dir]" can be removed.
if (m->lat_max[dir] < lat)
m->lat_max[dir] = lat;
if (m->lat_min[dir] > lat)
m->lat_min[dir] = lat;
Thanks,
Daejun
>
>Thanks,
>Can Guo
>
>>
>>> +
>>> + m->nr_queued[dir]--;
>>> + /* Push forward the busy start of monitor */
>>> + m->busy_start_ts[dir] = now;
>>> + }
>>> +}
>>
>> Thanks,
>> Daejun
