[PATCH 7/7] mm: vmscan: Immediately reclaim end-of-LRU dirty pages when writeback completes

Mel Gorman
2011-08-10T10:47:32Z

When direct reclaim encounters a dirty page, it gets recycled around
the LRU for another cycle. This patch marks the page PageReclaim
similar to 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>
Acked-by: Johannes Weiner <jweiner@redhat.com>
---
include/linux/mmzone.h | 2 +-
mm/vmscan.c | 10 +++++++++-
mm/vmstat.c | 2 +-
3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index b70a0c0..c9c5797 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_IMMEDIATE, /* Prioritise for reclaim when writeback ends */
NR_WRITEBACK_TEMP, /* Writeback using temporary buffers */
NR_ISOLATED_ANON, /* Temporary isolated pages from anon lru */
NR_ISOLATED_FILE, /* Temporary isolated pages from file lru */
diff --git a/mm/vmscan.c b/mm/vmscan.c
index b0437f2..33882a3 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -826,7 +826,15 @@ 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);
+ /*
+ * Immediately reclaim when written back.
+ * Similar in principal to deactivate_page()
+ * except we already have the page isolated
+ * and know it's dirty
+ */
+ inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
+ SetPageReclaim(page);
+
goto keep_locked;
}

diff --git a/mm/vmstat.c b/mm/vmstat.c
index fd109f3..471b20b 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_immediate_reclaim",
"nr_writeback_temp",
"nr_isolated_anon",
"nr_isolated_file",
--
1.7.3.4