Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757798Ab0LHB0i (ORCPT ); Tue, 7 Dec 2010 20:26:38 -0500 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:57388 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932468Ab0LHBC3 (ORCPT ); Tue, 7 Dec 2010 20:02:29 -0500 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Wed, 8 Dec 2010 09:56:42 +0900 From: KAMEZAWA Hiroyuki To: Minchan Kim Cc: Johannes Weiner , Andrew Morton , Rik van Riel , KOSAKI Motohiro , linux-mm , LKML , Peter Zijlstra , Wu Fengguang , Nick Piggin , Mel Gorman Subject: Re: [PATCH v4 2/7] deactivate invalidated pages Message-Id: <20101208095642.8128ab33.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: References: <20101207144923.GB2356@cmpxchg.org> <20101207150710.GA26613@barrios-desktop> <20101207151939.GF2356@cmpxchg.org> <20101207152625.GB608@barrios-desktop> <20101207155645.GG2356@cmpxchg.org> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 3.0.3 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3994 Lines: 82 On Wed, 8 Dec 2010 07:51:25 +0900 Minchan Kim wrote: > On Wed, Dec 8, 2010 at 12:56 AM, Johannes Weiner wrote: > > On Wed, Dec 08, 2010 at 12:26:25AM +0900, Minchan Kim wrote: > >> On Tue, Dec 07, 2010 at 04:19:39PM +0100, Johannes Weiner wrote: > >> > On Wed, Dec 08, 2010 at 12:07:10AM +0900, Minchan Kim wrote: > >> > > On Tue, Dec 07, 2010 at 03:49:24PM +0100, Johannes Weiner wrote: > >> > > > On Mon, Dec 06, 2010 at 02:29:10AM +0900, Minchan Kim wrote: > >> > > > > Changelog since v3: > >> > > > >  - Change function comments - suggested by Johannes > >> > > > >  - Change function name - suggested by Johannes > >> > > > >  - add only dirty/writeback pages to deactive pagevec > >> > > > > >> > > > Why the extra check? > >> > > > > >> > > > > @@ -359,8 +360,16 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping, > >> > > > >                       if (lock_failed) > >> > > > >                               continue; > >> > > > > > >> > > > > -                     ret += invalidate_inode_page(page); > >> > > > > - > >> > > > > +                     ret = invalidate_inode_page(page); > >> > > > > +                     /* > >> > > > > +                      * If the page is dirty or under writeback, we can not > >> > > > > +                      * invalidate it now.  But we assume that attempted > >> > > > > +                      * invalidation is a hint that the page is no longer > >> > > > > +                      * of interest and try to speed up its reclaim. > >> > > > > +                      */ > >> > > > > +                     if (!ret && (PageDirty(page) || PageWriteback(page))) > >> > > > > +                             deactivate_page(page); > >> > > > > >> > > > The writeback completion handler does not take the page lock, so you > >> > > > can still miss pages that finish writeback before this test, no? > >> > > > >> > > Yes. but I think it's rare and even though it happens, it's not critical. > >> > > > > >> > > > Can you explain why you felt the need to add these checks? > >> > > > >> > > invalidate_inode_page can return 0 although the pages is !{dirty|writeback}. > >> > > Look invalidate_complete_page. As easiest example, if the page has buffer and > >> > > try_to_release_page can't release the buffer, it could return 0. > >> > > >> > Ok, but somebody still tried to truncate the page, so why shouldn't we > >> > try to reclaim it?  The reason for deactivating at this location is > >> > that truncation is a strong hint for reclaim, not that it failed due > >> > to dirty/writeback pages. > >> > > >> > What's the problem with deactivating pages where try_to_release_page() > >> > failed? > >> > >> If try_to_release_page fails and the such pages stay long time in pagevec, > >> pagevec drain often happens. > > > > You mean because the pagevec becomes full more often?  These are not > > many pages you get extra without the checks, the race window is very > > small after all. > > Right. > It was a totally bad answer. The work in midnight makes my mind to be hurt. :) > > Another point is that we can move such pages(!try_to_release_page, > someone else holding the ref) into tail of inactive. > We can't expect such pages will be freed sooner or later and it can > stir lru pages unnecessary. > On the other hand it's a _really_ rare so couldn't we move the pages into tail? > If it can be justified, I will remove the check. > What do you think about it? > I wonder ...how about adding "victim" list for "Reclaim" pages ? Then, we don't need extra LRU rotation. Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/