diff mbox series

[07/10] writeback: factor out wb_dirty_freerun to remove more repeated freerun code

Message ID 20240429034738.138609-8-shikemeng@huaweicloud.com (mailing list archive)
State New, archived
Headers show
Series Add helper functions to remove repeated code and | expand

Commit Message

Kemeng Shi April 29, 2024, 3:47 a.m. UTC 
Factor out wb_dirty_freerun to remove more repeated freerun code.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
---
 mm/page-writeback.c | 55 +++++++++++++++++++++++----------------------
 1 file changed, 28 insertions(+), 27 deletions(-)

Comments

Tejun Heo May 1, 2024, 5:18 p.m. UTC | #1 
On Mon, Apr 29, 2024 at 11:47:35AM +0800, Kemeng Shi wrote:
...
> +static void wb_dirty_freerun(struct dirty_throttle_control *dtc,
> +			     bool strictlimit)
> +{
...
> +	/*
> +	 * LOCAL_THROTTLE tasks must not be throttled when below the per-wb
> +	 * freerun ceiling.
> +	 */
> +	if (!(current->flags & PF_LOCAL_THROTTLE))
> +		return;

Shouldn't this set free_run to true?

Also, wouldn't it be better if these functions return bool instead of
recording the result in dtc->freerun?

Thanks.
Kemeng Shi May 6, 2024, 1:53 a.m. UTC | #2 
Hello,
on 5/2/2024 1:18 AM, Tejun Heo wrote:
> On Mon, Apr 29, 2024 at 11:47:35AM +0800, Kemeng Shi wrote:
> ...
>> +static void wb_dirty_freerun(struct dirty_throttle_control *dtc,
>> +			     bool strictlimit)
>> +{
> ...
>> +	/*
>> +	 * LOCAL_THROTTLE tasks must not be throttled when below the per-wb
>> +	 * freerun ceiling.
>> +	 */
>> +	if (!(current->flags & PF_LOCAL_THROTTLE))
>> +		return;
> 
> Shouldn't this set free_run to true?
Originally, we will go freerun if PF_LOCAL_THROTTLE is set and number of dirty
pages is under freerun ceil. So if PF_LOCAL_THROTTLE is *not* set, freerun
should be false. Maybe I miss something and please correct me, Thanks.
> 
> Also, wouldn't it be better if these functions return bool instead of
> recording the result in dtc->freerun?
As I try to factor out balance_wb_limits to calculate freerun, dirty_exceeded
and position ratio of wb, so wb_dirty_freerun and wb_dirty_exceeded will be
called indirectly and balance_dirty_pages has to retrieve freerun and
dirty_exceeded from somewhere like dtc where position ratio is retrieved.
Would like to know any better idea.
Thanks.
> 
> Thanks.
>
diff mbox series

Patch

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index b49ca82380a5..e38beb680742 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1753,6 +1753,27 @@  static void domain_dirty_freerun(struct dirty_throttle_control *dtc,
 	dtc->freerun = dirty <= dirty_freerun_ceiling(thresh, bg_thresh);
 }
 
+static void wb_dirty_freerun(struct dirty_throttle_control *dtc,
+			     bool strictlimit)
+{
+	dtc->freerun = false;
+
+	/* was already handled in domain_dirty_freerun */
+	if (strictlimit)
+		return;
+
+	wb_dirty_limits(dtc);
+	/*
+	 * LOCAL_THROTTLE tasks must not be throttled when below the per-wb
+	 * freerun ceiling.
+	 */
+	if (!(current->flags & PF_LOCAL_THROTTLE))
+		return;
+
+	dtc->freerun = dtc->wb_dirty <
+		       dirty_freerun_ceiling(dtc->wb_thresh, dtc->wb_bg_thresh);
+}
+
 /*
  * balance_dirty_pages() must be called by processes which are generating dirty
  * data.  It looks at the number of dirty pages in the machine and will force
@@ -1845,19 +1866,9 @@  static int balance_dirty_pages(struct bdi_writeback *wb,
 		 * Calculate global domain's pos_ratio and select the
 		 * global dtc by default.
 		 */
-		if (!strictlimit) {
-			wb_dirty_limits(gdtc);
-
-			if ((current->flags & PF_LOCAL_THROTTLE) &&
-			    gdtc->wb_dirty <
-			    dirty_freerun_ceiling(gdtc->wb_thresh,
-						  gdtc->wb_bg_thresh))
-				/*
-				 * LOCAL_THROTTLE tasks must not be throttled
-				 * when below the per-wb freerun ceiling.
-				 */
-				goto free_running;
-		}
+		wb_dirty_freerun(gdtc, strictlimit);
+		if (gdtc->freerun)
+			goto free_running;
 
 		dirty_exceeded = (gdtc->wb_dirty > gdtc->wb_thresh) &&
 			((gdtc->dirty > gdtc->thresh) || strictlimit);
@@ -1872,20 +1883,10 @@  static int balance_dirty_pages(struct bdi_writeback *wb,
 			 * both global and memcg domains.  Choose the one
 			 * w/ lower pos_ratio.
 			 */
-			if (!strictlimit) {
-				wb_dirty_limits(mdtc);
-
-				if ((current->flags & PF_LOCAL_THROTTLE) &&
-				    mdtc->wb_dirty <
-				    dirty_freerun_ceiling(mdtc->wb_thresh,
-							  mdtc->wb_bg_thresh))
-					/*
-					 * LOCAL_THROTTLE tasks must not be
-					 * throttled when below the per-wb
-					 * freerun ceiling.
-					 */
-					goto free_running;
-			}
+			wb_dirty_freerun(mdtc, strictlimit);
+			if (mdtc->freerun)
+				goto free_running;
+
 			dirty_exceeded |= (mdtc->wb_dirty > mdtc->wb_thresh) &&
 				((mdtc->dirty > mdtc->thresh) || strictlimit);