The patch titled
Subject: mm-vmscan-throttle-reclaim-if-encountering-too-many-dirty-pages-under-writeback-update
has been removed from the -mm tree. Its filename was
mm-vmscan-throttle-reclaim-if-encountering-too-many-dirty-pages-under-writeback-update.patch
This patch was dropped because it was folded into mm-vmscan-throttle-reclaim-if-encountering-too-many-dirty-pages-under-writeback.patch
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
From: Mel Gorman <mgorman@xxxxxxx>
Subject: mm-vmscan-throttle-reclaim-if-encountering-too-many-dirty-pages-under-writeback-update
This patch expands on a comment on how we throttle from reclaim context.
It should be merged with
mm-vmscan-throttle-reclaim-if-encountering-too-many-dirty-pages-under-writeback.patch
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 26 +++++++++++++++++++++-----
1 file changed, 21 insertions(+), 5 deletions(-)
diff -puN mm/vmscan.c~mm-vmscan-throttle-reclaim-if-encountering-too-many-dirty-pages-under-writeback-update mm/vmscan.c
--- a/mm/vmscan.c~mm-vmscan-throttle-reclaim-if-encountering-too-many-dirty-pages-under-writeback-update
+++ a/mm/vmscan.c
@@ -1538,11 +1538,27 @@ shrink_inactive_list(unsigned long nr_to
putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
/*
- * If we have encountered a high number of dirty pages under writeback
- * then we are reaching the end of the LRU too quickly and global
- * limits are not enough to throttle processes due to the page
- * distribution throughout zones. Scale the number of dirty pages that
- * must be under writeback before being throttled to priority.
+ * If reclaim is isolating dirty pages under writeback, it implies
+ * that the long-lived page allocation rate is exceeding the page
+ * laundering rate. Either the global limits are not being effective
+ * at throttling processes due to the page distribution throughout
+ * zones or there is heavy usage of a slow backing device. The
+ * only option is to throttle from reclaim context which is not ideal
+ * as there is no guarantee the dirtying process is throttled in the
+ * same way balance_dirty_pages() manages.
+ *
+ * This scales the number of dirty pages that must be under writeback
+ * before throttling depending on priority. It is a simple backoff
+ * function that has the most effect in the range DEF_PRIORITY to
+ * DEF_PRIORITY-2 which is the priority reclaim is considered to be
+ * in trouble and reclaim is considered to be in trouble.
+ *
+ * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle
+ * DEF_PRIORITY-1 50% must be PageWriteback
+ * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble
+ * ...
+ * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
+ * isolated page is PageWriteback
*/
if (nr_writeback && nr_writeback >= (nr_taken >> (DEF_PRIORITY-priority)))
wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
_
Patches currently in -mm which might be from mgorman@xxxxxxx are
origin.patch
mm-compaction-trivial-clean-up-in-acct_isolated.patch
mm-change-isolate-mode-from-define-to-bitwise-type.patch
mm-compaction-make-isolate_lru_page-filter-aware.patch
mm-zone_reclaim-make-isolate_lru_page-filter-aware.patch
mm-migration-clean-up-unmap_and_move.patch
mm-vmscan-do-not-writeback-filesystem-pages-in-direct-reclaim.patch
mm-vmscan-remove-dead-code-related-to-lumpy-reclaim-waiting-on-pages-under-writeback.patch
xfs-warn-if-direct-reclaim-tries-to-writeback-pages.patch
ext4-warn-if-direct-reclaim-tries-to-writeback-pages.patch
mm-vmscan-do-not-writeback-filesystem-pages-in-kswapd-except-in-high-priority.patch
mm-vmscan-throttle-reclaim-if-encountering-too-many-dirty-pages-under-writeback.patch
mm-vmscan-immediately-reclaim-end-of-lru-dirty-pages-when-writeback-completes.patch
vmscan-count-pages-into-balanced-for-zone-with-good-watermark.patch
mremap-check-for-overflow-using-deltas.patch
mremap-avoid-sending-one-ipi-per-page.patch
thp-mremap-support-and-tlb-optimization.patch
thp-mremap-support-and-tlb-optimization-fix.patch
thp-mremap-support-and-tlb-optimization-fix-fix.patch
kswapd-avoid-unnecessary-rebalance-after-an-unsuccessful-balancing.patch
kswapd-assign-new_order-and-new_classzone_idx-after-wakeup-in-sleeping.patch
vmscan-limit-direct-reclaim-for-higher-order-allocations.patch
vmscan-limit-direct-reclaim-for-higher-order-allocations-fix.patch
vmscan-abort-reclaim-compaction-if-compaction-can-proceed.patch
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