From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx167.postini.com [74.125.245.167]) by kanga.kvack.org (Postfix) with SMTP id C56A26B004F for ; Thu, 26 Jan 2012 16:28:04 -0500 (EST) MIME-Version: 1.0 Message-ID: <9fcd06f5-360e-4542-9fbb-f8c7efb28cb6@default> Date: Thu, 26 Jan 2012 13:28:02 -0800 (PST) From: Dan Magenheimer Subject: RE: [PATCH] mm: implement WasActive page flag (for improving cleancache) References: <4F218D36.2060308@linux.vnet.ibm.com> In-Reply-To: <4F218D36.2060308@linux.vnet.ibm.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Konrad Wilk , Seth Jennings , Nitin Gupta , Nebojsa Trpkovic , minchan@kernel.org, KAMEZAWA Hiroyuki , riel@redhat.com, Chris Mason > From: Dave Hansen [mailto:dave@linux.vnet.ibm.com] > Subject: Re: [PATCH] mm: implement WasActive page flag (for improving cle= ancache) Thanks for the review Dave! =20 > On 01/25/2012 01:58 PM, Dan Magenheimer wrote: > > (Feedback welcome if there is a different/better way to do this > > without using a page flag!) > > > > Since about 2.6.27, the page replacement algorithm maintains > > an "active" bit to help decide which pages are most eligible > > to reclaim, see http://linux-mm.org/PageReplacementDesign > > > > This "active' information is also useful to cleancache but is lost > > by the time that cleancache has the opportunity to preserve the > > pageful of data. This patch adds a new page flag "WasActive" to > > retain the state. The flag may possibly be useful elsewhere. >=20 > I guess cleancache itself is clearing the bit, right? I didn't see any > clearing going on in the patch. No, there are no changes in cleancache.c so it isn't clearing the bit. > I do think it also needs to get cleared on the way in to the page > allocator. Otherwise: >=20 > =09PageSetWasActive(page); > =09free_page(page); > =09... > =09another_user_page =3D get_free_page() > =09// now cleancache sees the active bit for the prev user >=20 > Or am I missing somewhere it gets cleared non-explicitly somewhere? True, it is not getting cleared and it should be, good catch! I'll find the place to add the call to ClearPageWasActive() for v2. Thanks, Dan -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org