vmscan: clear ZONE_CONGESTED for zone with good watermark
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@intel.com> Acked-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
4c30c6f566
commit
439423f689
|
@ -2529,6 +2529,9 @@ loop_again:
|
||||||
high_wmark_pages(zone), 0, 0)) {
|
high_wmark_pages(zone), 0, 0)) {
|
||||||
end_zone = i;
|
end_zone = i;
|
||||||
break;
|
break;
|
||||||
|
} else {
|
||||||
|
/* If balanced, clear the congested flag */
|
||||||
|
zone_clear_flag(zone, ZONE_CONGESTED);
|
||||||
}
|
}
|
||||||
}
|
}
|
||||||
if (i < 0)
|
if (i < 0)
|
||||||
|
|
Loading…
Reference in New Issue