[PATCH 3/3] vmscan: Put kswapd to sleep on its own waitqueue, not congestion
in [Kernel]
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From: Mel Gorman on 8 Mar 2010 06:50 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(a)csn.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(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |