From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id E9EA16B004D for ; Fri, 13 Nov 2009 15:04:04 -0500 (EST) Date: Fri, 13 Nov 2009 20:03:57 +0000 From: Mel Gorman Subject: [PATCH] vmscan: Stop kswapd waiting on congestion when the min watermark is not being met V2 Message-ID: <20091113200357.GO29804@csn.ul.ie> References: <20091113142608.33B9.A69D9226@jp.fujitsu.com> <20091113135443.GF29804@csn.ul.ie> <20091114023138.3DA5.A69D9226@jp.fujitsu.com> <20091113181557.GM29804@csn.ul.ie> <2f11576a0911131033w4a9e6042k3349f0be290a167e@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <2f11576a0911131033w4a9e6042k3349f0be290a167e@mail.gmail.com> Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: KOSAKI Motohiro , Frans Pop , Jiri Kosina , Sven Geggus , Karol Lewandowski , Tobias Oetiker , linux-kernel@vger.kernel.org, "linux-mm@kvack.org" , Pekka Enberg , Rik van Riel , Christoph Lameter , Stephan von Krawczynski , "Rafael J. Wysocki" , Kernel Testers List List-ID: The last version has a stupid bug in it. Sorry. Changelog since V1 o Fix incorrect negation o Rename kswapd_no_congestion_wait to kswapd_skip_congestion_wait as suggested by Rik If reclaim fails to make sufficient progress, the priority is raised. Once the priority is higher, kswapd starts waiting on congestion. However, if the zone is below the min watermark then kswapd needs to continue working without delay as there is a danger of an increased rate of GFP_ATOMIC allocation failure. This patch changes the conditions under which kswapd waits on congestion by only going to sleep if the min watermarks are being met. [mel@csn.ul.ie: Add stats to track how relevant the logic is] From: KOSAKI Motohiro Signed-off-by: KOSAKI Motohiro Signed-off-by: Mel Gorman Reviewed-by: Rik van Riel --- include/linux/vmstat.h | 1 + mm/vmscan.c | 18 ++++++++++++++++-- mm/vmstat.c | 1 + 3 files changed, 18 insertions(+), 2 deletions(-) diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h index 9716003..7d66695 100644 --- a/include/linux/vmstat.h +++ b/include/linux/vmstat.h @@ -41,6 +41,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, #endif PGINODESTEAL, SLABS_SCANNED, KSWAPD_STEAL, KSWAPD_INODESTEAL, KSWAPD_PREMATURE_FAST, KSWAPD_PREMATURE_SLOW, + KSWAPD_SKIP_CONGESTION_WAIT, PAGEOUTRUN, ALLOCSTALL, PGROTATED, #ifdef CONFIG_HUGETLB_PAGE HTLB_BUDDY_PGALLOC, HTLB_BUDDY_PGALLOC_FAIL, diff --git a/mm/vmscan.c b/mm/vmscan.c index ffa1766..70a2322 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1979,6 +1979,7 @@ loop_again: for (priority = DEF_PRIORITY; priority >= 0; priority--) { int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ unsigned long lru_pages = 0; + int has_under_min_watermark_zone = 0; /* The swap token gets in the way of swapout... */ if (!priority) @ -2085,6 +2086,15 @@ loop_again: if (total_scanned > SWAP_CLUSTER_MAX * 2 && total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) sc.may_writepage = 1; + + /* + * We are still under min water mark. it mean we have + * GFP_ATOMIC allocation failure risk. Hurry up! + */ + if (!zone_watermark_ok(zone, order, min_wmark_pages(zone), + end_zone, 0)) + has_under_min_watermark_zone = 1; + } if (all_zones_ok) break; /* kswapd: all done */ @@ -2092,8 +2102,12 @@ loop_again: * OK, kswapd is getting into trouble. Take a nap, then take * another pass across the zones. */ - if (total_scanned && priority < DEF_PRIORITY - 2) - congestion_wait(BLK_RW_ASYNC, HZ/10); + 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); + } /* * We do this so kswapd doesn't build up large priorities for diff --git a/mm/vmstat.c b/mm/vmstat.c index 90b11e4..bc09547 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -685,6 +685,7 @@ static const char * const vmstat_text[] = { "kswapd_inodesteal", "kswapd_slept_prematurely_fast", "kswapd_slept_prematurely_slow", + "kswapd_skip_congestion_wait", "pageoutrun", "allocstall", -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org