From: Stanley Chu <stanley.chu@mediatek.com>
To: <linux-scsi@vger.kernel.org>, <martin.petersen@oracle.com>,
<avri.altman@wdc.com>, <alim.akhtar@samsung.com>,
<jejb@linux.ibm.com>, <asutoshd@codeaurora.org>
Cc: <beanhuo@micron.com>, <cang@codeaurora.org>,
<matthias.bgg@gmail.com>, <bvanassche@acm.org>,
<linux-mediatek@lists.infradead.org>,
<linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, <kuohong.wang@mediatek.com>,
<peter.wang@mediatek.com>, <chun-hung.wu@mediatek.com>,
<andy.teng@mediatek.com>, <chaotian.jing@mediatek.com>,
<cc.chou@mediatek.com>, Stanley Chu <stanley.chu@mediatek.com>
Subject: [PATCH v3] scsi: ufs: Fix imprecise load calculation in devfreq window
Date: Wed, 10 Jun 2020 22:42:30 +0800 [thread overview]
Message-ID: <20200610144230.2127-1-stanley.chu@mediatek.com> (raw)
The UFS load calculation is based on total_time and busy_time in a
devfreq window. However, the precision of both time are different.
busy_time is assigned from "jiffies" thus has different accuracy
from total_time which is assigned from ktime_get().
To guarantee the precision of load calculation, we need to
1. Align time accuracy of both devfreq_dev_status.total_time and
devfreq_dev_status.busy_time. For example, use "ktime_get()"
directly.
2. Align below timelines,
- The beginning time of devfreq windows
- The beginning of busy time in a new window
- The end of busy time in the current window
Fixes: a3cd5ec55f6c ("scsi: ufs: add load based scaling of UFS gear")
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
---
drivers/scsi/ufs/ufshcd.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index ad4fc829cbb2..04b79ca66fdf 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1314,6 +1314,7 @@ static int ufshcd_devfreq_get_dev_status(struct device *dev,
unsigned long flags;
struct list_head *clk_list = &hba->clk_list_head;
struct ufs_clk_info *clki;
+ ktime_t curr_t;
if (!ufshcd_is_clkscaling_supported(hba))
return -EINVAL;
@@ -1321,6 +1322,7 @@ static int ufshcd_devfreq_get_dev_status(struct device *dev,
memset(stat, 0, sizeof(*stat));
spin_lock_irqsave(hba->host->host_lock, flags);
+ curr_t = ktime_get();
if (!scaling->window_start_t)
goto start_window;
@@ -1332,18 +1334,17 @@ static int ufshcd_devfreq_get_dev_status(struct device *dev,
*/
stat->current_frequency = clki->curr_freq;
if (scaling->is_busy_started)
- scaling->tot_busy_t += ktime_to_us(ktime_sub(ktime_get(),
+ scaling->tot_busy_t += ktime_to_us(ktime_sub(curr_t,
scaling->busy_start_t));
- stat->total_time = jiffies_to_usecs((long)jiffies -
- (long)scaling->window_start_t);
+ stat->total_time = ktime_to_us(curr_t) - scaling->window_start_t;
stat->busy_time = scaling->tot_busy_t;
start_window:
- scaling->window_start_t = jiffies;
+ scaling->window_start_t = ktime_to_us(curr_t);
scaling->tot_busy_t = 0;
if (hba->outstanding_reqs) {
- scaling->busy_start_t = ktime_get();
+ scaling->busy_start_t = curr_t;
scaling->is_busy_started = true;
} else {
scaling->busy_start_t = 0;
--
2.18.0
reply other threads:[~2020-06-10 14:42 UTC|newest]
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