Messages in this thread | | | Date | Tue, 06 Apr 2021 13:37:28 +0800 | From | Can Guo <> | Subject | Re: [PATCH 1/2] scsi: ufs: Introduce hba performance monitor sysfs nodes |
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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?
> >> + } >> + >> +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.
> >> + 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?
Thanks, Can Guo
> >> + >> + m->nr_queued[dir]--; >> + /* Push forward the busy start of monitor */ >> + m->busy_start_ts[dir] = now; >> + } >> +} > > Thanks, > Daejun
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