linux-kernel - [PATCH 3/3] vmscan: Put kswapd to sleep on its own waitqueue, not congestion

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon,  8 Mar 2010 11:48:23 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	linux-mm@...ck.org
Cc:	Nick Piggin <npiggin@...e.de>,
	Christian Ehrhardt <ehrhardt@...ux.vnet.ibm.com>,
	Chris Mason <chris.mason@...cle.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	linux-kernel@...r.kernel.org, Mel Gorman <mel@....ul.ie>
Subject: [PATCH 3/3] vmscan: Put kswapd to sleep on its own waitqueue, not congestion

If kswapd is raising its priority to get the zone over the high
watermark, it may call congestion_wait() ostensibly to allow congestion
to clear. However, there is no guarantee that the queue is congested at
this point because it depends on kswapds previous actions as well as the
rest of the system. Kswapd could simply be working hard because there is
a lot of SYNC traffic in which case it shouldn't be sleeping.

Rather than waiting on congestion and potentially sleeping for longer
than it should, this patch puts kswapd back to sleep on the kswapd_wait
queue for the timeout. If direct reclaimers are in trouble, kswapd will
be rewoken as it should instead of sleeping when there is work to be
done.

Signed-off-by: Mel Gorman <mel@....ul.ie>
---
 mm/vmscan.c |   11 +++++++----
 1 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4f92a48..894d366 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1955,7 +1955,7 @@ static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
  * interoperates with the page allocator fallback scheme to ensure that aging
  * of pages is balanced across the zones.
  */
-static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
+static unsigned long balance_pgdat(pg_data_t *pgdat, wait_queue_t *wait, int order)
 {
 	int all_zones_ok;
 	int priority;
@@ -2122,8 +2122,11 @@ loop_again:
 		if (total_scanned && (priority < DEF_PRIORITY - 2)) {
 			if (has_under_min_watermark_zone)
 				count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
-			else
-				congestion_wait(BLK_RW_ASYNC, HZ/10);
+			else {
+				prepare_to_wait(&pgdat->kswapd_wait, wait, TASK_INTERRUPTIBLE);
+				schedule_timeout(HZ/10);
+				finish_wait(&pgdat->kswapd_wait, wait);
+			}
 		}
 
 		/*
@@ -2272,7 +2275,7 @@ static int kswapd(void *p)
 		 * after returning from the refrigerator
 		 */
 		if (!ret)
-			balance_pgdat(pgdat, order);
+			balance_pgdat(pgdat, &wait, order);
 	}
 	return 0;
 }
-- 
1.6.5

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/