The patch titled
vmscan: clear ZONE_CONGESTED for zone with good watermark -resend
has been added to the -mm tree. Its filename is
vmscan-clear-zone_congested-for-zone-with-good-watermark-resend.patch
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Subject: vmscan: clear ZONE_CONGESTED for zone with good watermark -resend
From: Shaohua Li <shaohua.li@xxxxxxxxx>
ZONE_CONGESTED is only cleared in kswapd, but pages can be freed in any
task. It's possible ZONE_CONGESTED isn't cleared in some cases: 1. the
zone is already balanced just entering balance_pgdat() for order-0 because
concurrent tasks free memory. In this case, later check will skip the
zone as it's balanced so the flag isn't cleared. 2. high order balance
fallbacks to order-0. quote from Mel: At the end of balance_pgdat(),
kswapd uses the following logic;
If reclaiming at high order {
for each zone {
if all_unreclaimable
skip
if watermark is not met
order = 0
loop again
/* watermark is met */
clear congested
}
}
i.e. it clears ZONE_CONGESTED if it the zone is balanced. if not, it
restarts balancing at order-0. However, if the higher zones are balanced
for order-0, kswapd will miss clearing ZONE_CONGESTED as that only happens
after a zone is shrunk. This can mean that wait_iff_congested() stalls
unnecessarily. This patch makes kswapd clear ZONE_CONGESTED during its
initial highmem->dma scan for zones that are already balanced.
Signed-off-by: Shaohua Li <shaohua.li@xxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxx>
Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 3 +++
1 file changed, 3 insertions(+)
diff -puN mm/vmscan.c~vmscan-clear-zone_congested-for-zone-with-good-watermark-resend mm/vmscan.c
--- a/mm/vmscan.c~vmscan-clear-zone_congested-for-zone-with-good-watermark-resend
+++ a/mm/vmscan.c
@@ -2529,6 +2529,9 @@ loop_again:
high_wmark_pages(zone), 0, 0)) {
end_zone = i;
break;
+ } else {
+ /* If balanced, clear the congested flag */
+ zone_clear_flag(zone, ZONE_CONGESTED);
}
}
if (i < 0)
_
Patches currently in -mm which might be from shaohua.li@xxxxxxxxx are
origin.patch
mm-fix-a-vmscan-warning.patch
vmscan-clear-zone_congested-for-zone-with-good-watermark-resend.patch
linux-next.patch
vmscan-add-block-plug-for-page-reclaim.patch
vmscan-count-pages-into-balanced-for-zone-with-good-watermark.patch
intel_idle-fix-api-misuse.patch
intel_idle-disable-auto_demotion-for-hotplugged-cpus.patch
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