The patch titled
Subject: mm/page-writeback: consolidate wb_thresh bumping logic into __wb_calc_thresh
has been added to the -mm mm-unstable branch. Its filename is
mm-page-writeback-consolidate-wb_thresh-bumping-logic-into-__wb_calc_thresh.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page-writeback-consolidate-wb_thresh-bumping-logic-into-__wb_calc_thresh.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Jim Zhao <jimzhao.ai@xxxxxxxxx>
Subject: mm/page-writeback: consolidate wb_thresh bumping logic into __wb_calc_thresh
Date: Thu, 21 Nov 2024 18:05:39 +0800
Address the feedback from 39ac99852fca ("mm/page-writeback: raise
wb_thresh to prevent write blocking with strictlimit)". The wb_thresh
bumping logic is scattered across wb_position_ratio, __wb_calc_thresh, and
wb_update_dirty_ratelimit. For consistency, consolidate all wb_thresh
bumping logic into __wb_calc_thresh.
Link: https://lkml.kernel.org/r/20241121100539.605818-1-jimzhao.ai@xxxxxxxxx
Signed-off-by: Jim Zhao <jimzhao.ai@xxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page-writeback.c | 53 ++++++++++++------------------------------
1 file changed, 16 insertions(+), 37 deletions(-)
--- a/mm/page-writeback.c~mm-page-writeback-consolidate-wb_thresh-bumping-logic-into-__wb_calc_thresh
+++ a/mm/page-writeback.c
@@ -936,26 +936,25 @@ static unsigned long __wb_calc_thresh(st
wb_min_max_ratio(wb, &wb_min_ratio, &wb_max_ratio);
wb_thresh += (thresh * wb_min_ratio) / (100 * BDI_RATIO_SCALE);
- wb_max_thresh = thresh * wb_max_ratio / (100 * BDI_RATIO_SCALE);
- if (wb_thresh > wb_max_thresh)
- wb_thresh = wb_max_thresh;
/*
- * With strictlimit flag, the wb_thresh is treated as
- * a hard limit in balance_dirty_pages() and wb_position_ratio().
- * It's possible that wb_thresh is close to zero, not because
- * the device is slow, but because it has been inactive.
- * To prevent occasional writes from being blocked, we raise wb_thresh.
+ * It's very possible that wb_thresh is close to 0 not because the
+ * device is slow, but that it has remained inactive for long time.
+ * Honour such devices a reasonable good (hopefully IO efficient)
+ * threshold, so that the occasional writes won't be blocked and active
+ * writes can rampup the threshold quickly.
*/
- if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) {
- unsigned long limit = hard_dirty_limit(dom, dtc->thresh);
- u64 wb_scale_thresh = 0;
-
- if (limit > dtc->dirty)
- wb_scale_thresh = (limit - dtc->dirty) / 100;
- wb_thresh = max(wb_thresh, min(wb_scale_thresh, wb_max_thresh / 4));
+ if (thresh > dtc->dirty) {
+ if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT))
+ wb_thresh = max(wb_thresh, (thresh - dtc->dirty) / 100);
+ else
+ wb_thresh = max(wb_thresh, (thresh - dtc->dirty) / 8);
}
+ wb_max_thresh = thresh * wb_max_ratio / (100 * BDI_RATIO_SCALE);
+ if (wb_thresh > wb_max_thresh)
+ wb_thresh = wb_max_thresh;
+
return wb_thresh;
}
@@ -963,6 +962,7 @@ unsigned long wb_calc_thresh(struct bdi_
{
struct dirty_throttle_control gdtc = { GDTC_INIT(wb) };
+ domain_dirty_avail(&gdtc, true);
return __wb_calc_thresh(&gdtc, thresh);
}
@@ -1139,12 +1139,6 @@ static void wb_position_ratio(struct dir
if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) {
long long wb_pos_ratio;
- if (dtc->wb_dirty < 8) {
- dtc->pos_ratio = min_t(long long, pos_ratio * 2,
- 2 << RATELIMIT_CALC_SHIFT);
- return;
- }
-
if (dtc->wb_dirty >= wb_thresh)
return;
@@ -1216,14 +1210,6 @@ static void wb_position_ratio(struct dir
if (unlikely(wb_thresh > dtc->thresh))
wb_thresh = dtc->thresh;
/*
- * It's very possible that wb_thresh is close to 0 not because the
- * device is slow, but that it has remained inactive for long time.
- * Honour such devices a reasonable good (hopefully IO efficient)
- * threshold, so that the occasional writes won't be blocked and active
- * writes can rampup the threshold quickly.
- */
- wb_thresh = max(wb_thresh, (limit - dtc->dirty) / 8);
- /*
* scale global setpoint to wb's:
* wb_setpoint = setpoint * wb_thresh / thresh
*/
@@ -1478,17 +1464,10 @@ static void wb_update_dirty_ratelimit(st
* balanced_dirty_ratelimit = task_ratelimit * write_bw / dirty_rate).
* Hence, to calculate "step" properly, we have to use wb_dirty as
* "dirty" and wb_setpoint as "setpoint".
- *
- * We rampup dirty_ratelimit forcibly if wb_dirty is low because
- * it's possible that wb_thresh is close to zero due to inactivity
- * of backing device.
*/
if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) {
dirty = dtc->wb_dirty;
- if (dtc->wb_dirty < 8)
- setpoint = dtc->wb_dirty + 1;
- else
- setpoint = (dtc->wb_thresh + dtc->wb_bg_thresh) / 2;
+ setpoint = (dtc->wb_thresh + dtc->wb_bg_thresh) / 2;
}
if (dirty < setpoint) {
_
Patches currently in -mm which might be from jimzhao.ai@xxxxxxxxx are
mm-page-writeback-consolidate-wb_thresh-bumping-logic-into-__wb_calc_thresh.patch
