[PATCH 4/5] mm: vmscan: Immediately reclaim end-of-LRU dirty pages when writeback completes

Mel Gorman
2011-07-13T14:31:36Z

When direct reclaim encounters a dirty page, it gets recycled around
the LRU for another cycle. This patch marks the page PageReclaim using
deactivate_page() so that the page gets reclaimed almost immediately
after the page gets cleaned. This is to avoid reclaiming clean pages
that are younger than a dirty page encountered at the end of the LRU
that might have been something like a use-once page.

Signed-off-by: Mel Gorman <mgorman@suse.de>
---
include/linux/mmzone.h | 2 +-
mm/vmscan.c | 10 ++++++++--
mm/vmstat.c | 2 +-
3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index c4508a2..bea7858 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -100,7 +100,7 @@ enum zone_stat_item {
NR_UNSTABLE_NFS, /* NFS unstable pages */
NR_BOUNCE,
NR_VMSCAN_WRITE,
- NR_VMSCAN_WRITE_SKIP,
+ NR_VMSCAN_INVALIDATE,
NR_VMSCAN_THROTTLED,
NR_WRITEBACK_TEMP, /* Writeback using temporary buffers */
NR_ISOLATED_ANON, /* Temporary isolated pages from anon lru */
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9826086..8e00aee 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -834,8 +834,13 @@ static unsigned long shrink_page_list(struct list_head *page_list,
*/
if (page_is_file_cache(page) &&
(!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) {
- inc_zone_page_state(page, NR_VMSCAN_WRITE_SKIP);
- goto keep_locked;
+ inc_zone_page_state(page, NR_VMSCAN_INVALIDATE);
+
+ /* Immediately reclaim when written back */
+ unlock_page(page);
+ deactivate_page(page);
+
+ goto keep_dirty;
}

if (references == PAGEREF_RECLAIM_CLEAN)
@@ -956,6 +961,7 @@ keep:
reset_reclaim_mode(sc);
keep_lumpy:
list_add(&page->lru, &ret_pages);
+keep_dirty:
VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
}

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 59ee17c..2c82ae5 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -702,7 +702,7 @@ const char * const vmstat_text[] = {
"nr_unstable",
"nr_bounce",
"nr_vmscan_write",
- "nr_vmscan_write_skip",
+ "nr_vmscan_invalidate",
"nr_vmscan_throttled",
"nr_writeback_temp",
"nr_isolated_anon",
--
1.7.3.4