From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id F2D6C6B008C for ; Tue, 7 Dec 2010 20:02:26 -0500 (EST) Received: from m2.gw.fujitsu.co.jp ([10.0.50.72]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id oB812OBX011954 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Wed, 8 Dec 2010 10:02:24 +0900 Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 511EF45DE6A for ; Wed, 8 Dec 2010 10:02:24 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 3898045DD74 for ; Wed, 8 Dec 2010 10:02:24 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id EC5541DB803B for ; Wed, 8 Dec 2010 10:02:23 +0900 (JST) Received: from ml13.s.css.fujitsu.com (ml13.s.css.fujitsu.com [10.249.87.103]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id AC263E18008 for ; Wed, 8 Dec 2010 10:02:23 +0900 (JST) Date: Wed, 8 Dec 2010 09:56:42 +0900 From: KAMEZAWA Hiroyuki 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> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: Johannes Weiner , Andrew Morton , Rik van Riel , KOSAKI Motohiro , linux-mm , LKML , Peter Zijlstra , Wu Fengguang , Nick Piggin , Mel Gorman List-ID: 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: > >> > > > > A - Change function comments - suggested by Johannes > >> > > > > A - Change function name - suggested by Johannes > >> > > > > A - 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, > >> > > > > A A A A A A A A A A A if (lock_failed) > >> > > > > A A A A A A A A A A A A A A A continue; > >> > > > > > >> > > > > - A A A A A A A A A A ret += invalidate_inode_page(page); > >> > > > > - > >> > > > > + A A A A A A A A A A ret = invalidate_inode_page(page); > >> > > > > + A A A A A A A A A A /* > >> > > > > + A A A A A A A A A A A * If the page is dirty or under writeback, we can not > >> > > > > + A A A A A A A A A A A * invalidate it now. A But we assume that attempted > >> > > > > + A A A A A A A A A A A * invalidation is a hint that the page is no longer > >> > > > > + A A A A A A A A A A A * of interest and try to speed up its reclaim. > >> > > > > + A A A A A A A A A A A */ > >> > > > > + A A A A A A A A A A if (!ret && (PageDirty(page) || PageWriteback(page))) > >> > > > > + A A A A A A A A A A A A A A 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? A 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? A 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, 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 policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org