From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 3F61B600068 for ; Mon, 4 Jan 2010 00:52:41 -0500 (EST) Received: from m6.gw.fujitsu.co.jp ([10.0.50.76]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o045qbnQ014218 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Mon, 4 Jan 2010 14:52:38 +0900 Received: from smail (m6 [127.0.0.1]) by outgoing.m6.gw.fujitsu.co.jp (Postfix) with ESMTP id 9D5B045DE50 for ; Mon, 4 Jan 2010 14:52:37 +0900 (JST) Received: from s6.gw.fujitsu.co.jp (s6.gw.fujitsu.co.jp [10.0.50.96]) by m6.gw.fujitsu.co.jp (Postfix) with ESMTP id 6FB6145DE4C for ; Mon, 4 Jan 2010 14:52:37 +0900 (JST) Received: from s6.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s6.gw.fujitsu.co.jp (Postfix) with ESMTP id 4C2801DB803F for ; Mon, 4 Jan 2010 14:52:37 +0900 (JST) Received: from m105.s.css.fujitsu.com (m105.s.css.fujitsu.com [10.249.87.105]) by s6.gw.fujitsu.co.jp (Postfix) with ESMTP id F2E261DB8037 for ; Mon, 4 Jan 2010 14:52:36 +0900 (JST) From: KOSAKI Motohiro Subject: [PATCH] page allocator: fix update NR_FREE_PAGES only as necessary In-Reply-To: <20100104122138.f54b7659.minchan.kim@barrios-desktop> References: <1262571730-2778-1-git-send-email-shijie8@gmail.com> <20100104122138.f54b7659.minchan.kim@barrios-desktop> Message-Id: <20100104144332.96A2.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Date: Mon, 4 Jan 2010 14:52:36 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: kosaki.motohiro@jp.fujitsu.com, Huang Shijie , akpm@linux-foundation.org, mel@csn.ul.ie, linux-mm@kvack.org List-ID: > Hi, Huang.=20 >=20 > On Mon, 4 Jan 2010 10:22:10 +0800 > Huang Shijie wrote: >=20 > > When the `page' returned by __rmqueue() is NULL, the origin code > > still adds -(1 << order) to zone's NR_FREE_PAGES item. > >=20 > > The patch fixes it. > >=20 > > Signed-off-by: Huang Shijie > > --- > > mm/page_alloc.c | 10 +++++++--- > > 1 files changed, 7 insertions(+), 3 deletions(-) > >=20 > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 4e9f5cc..620921d 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -1222,10 +1222,14 @@ again: > > } > > spin_lock_irqsave(&zone->lock, flags); > > page =3D __rmqueue(zone, order, migratetype); > > - __mod_zone_page_state(zone, NR_FREE_PAGES, -(1 << order)); > > - spin_unlock(&zone->lock); > > - if (!page) > > + if (likely(page)) { > > + __mod_zone_page_state(zone, NR_FREE_PAGES, > > + -(1 << order)); > > + spin_unlock(&zone->lock); > > + } else { > > + spin_unlock(&zone->lock); > > goto failed; > > + } > > } > > =20 > > __count_zone_vm_events(PGALLOC, zone, 1 << order); >=20 > I think it's not desirable to add new branch in hot-path even though > we could avoid that.=20 >=20 > How about this? >=20 > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 4e4b5b3..87976ad 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1244,6 +1244,9 @@ again: > return page; > =20 > failed: > + spin_lock(&zone->lock); > + __mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order); > + spin_unlock(&zone->lock); > local_irq_restore(flags); > put_cpu(); > return NULL; Why can't we write following? __mod_zone_page_state() only require irq disabling, it doesn't need spin lock. I think. =46rom 72011ff2b0bba6544ae35c6ee52715c8c824a34b Mon Sep 17 00:00:00 2001 From: KOSAKI Motohiro Date: Mon, 4 Jan 2010 14:38:20 +0900 Subject: [PATCH] page allocator: fix update NR_FREE_PAGES only as necessary commit f2260e6b (page allocator: update NR_FREE_PAGES only as necessary) made one minor regression. if __rmqueue() was failed, NR_FREE_PAGES stat go wrong. this patch fixes it. Signed-off-by: KOSAKI Motohiro Cc: Mel Gorman Cc: Huang Shijie Cc: Minchan Kim --- mm/page_alloc.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 11ae66e..ecf75a1 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1227,10 +1227,10 @@ again: } spin_lock_irqsave(&zone->lock, flags); page =3D __rmqueue(zone, order, migratetype); - __mod_zone_page_state(zone, NR_FREE_PAGES, -(1 << order)); spin_unlock(&zone->lock); if (!page) goto failed; + __mod_zone_page_state(zone, NR_FREE_PAGES, -(1 << order)); } =20 __count_zone_vm_events(PGALLOC, zone, 1 << order); --=20 1.6.5.2 -- 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