Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751343Ab0KWFxU (ORCPT ); Tue, 23 Nov 2010 00:53:20 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:58791 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751057Ab0KWFxT (ORCPT ); Tue, 23 Nov 2010 00:53:19 -0500 Date: Mon, 22 Nov 2010 21:48:14 -0800 From: Andrew Morton To: Minchan Kim Cc: linux-mm , LKML , Peter Zijlstra , Rik van Riel , KOSAKI Motohiro , Johannes Weiner , Nick Piggin , Mel Gorman Subject: Re: [RFC 1/2] deactive invalidated pages Message-Id: <20101122214814.36c209a6.akpm@linux-foundation.org> In-Reply-To: References: <20101122141449.9de58a2c.akpm@linux-foundation.org> <20101122210132.be9962c7.akpm@linux-foundation.org> <20101122212220.ae26d9a5.akpm@linux-foundation.org> X-Mailer: Sylpheed 2.7.1 (GTK+ 2.18.9; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3446 Lines: 83 On Tue, 23 Nov 2010 14:45:15 +0900 Minchan Kim wrote: > On Tue, Nov 23, 2010 at 2:22 PM, Andrew Morton > wrote: > > On Tue, 23 Nov 2010 14:23:33 +0900 Minchan Kim wrote: > > > >> On Tue, Nov 23, 2010 at 2:01 PM, Andrew Morton > >> wrote: > >> > On Tue, 23 Nov 2010 13:52:05 +0900 Minchan Kim wrote: > >> > > >> >> >> +/* > >> >> >> + * Function used to forecefully demote a page to the head of the inactive > >> >> >> + * list. > >> >> >> + */ > >> >> > > >> >> > This comment is wrong? __The page gets moved to the _tail_ of the > >> >> > inactive list? > >> >> > >> >> No. I add it in _head_ of the inactive list intentionally. > >> >> Why I don't add it to _tail_ is that I don't want to be aggressive. > >> >> The page might be real working set. So I want to give a chance to > >> >> activate it again. > >> > > >> > Well.. __why? __The user just tried to toss the page away altogether. __If > >> > the kernel wasn't able to do that immediately, the best it can do is to > >> > toss the page away asap? > >> > > >> >> If it's not working set, it can be reclaimed easily and it can prevent > >> >> active page demotion since inactive list size would be big enough for > >> >> not calling shrink_active_list. > >> > > >> > What is "working set"? __Mapped and unmapped pagecache, or are you > >> > referring solely to mapped pagecache? > >> > >> I mean it's mapped by other processes. > >> > >> > > >> > If it's mapped pagecache then the user was being a bit silly (or didn't > >> > know that some other process had mapped the file). __In which case we > >> > need to decide what to do - leave the page alone, deactivate it, or > >> > half-deactivate it as this patch does. > >> > >> > >> What I want is the half-deactivate. > >> > >> Okay. We will use the result of invalidate_inode_page. > >> If fail happens by page_mapped, we can do half-deactivate. > >> But if fail happens by dirty(ex, writeback), we can add it to tail. > >> Does it make sense? > > > > Spose so. __It's unobvious. > > > > If the page is dirty or under writeback then reclaim will immediately > > move it to the head of the LRU anyway. __But given that the user has > > Why does it move into head of LRU? > If the page which isn't mapped doesn't have PG_referenced, it would be > reclaimed. If it's dirty or under writeback it can't be reclaimed! > > just freed a bunch of pages with invalidate(), it's unlikely that > > reclaim will be running soon. > > If reclaim doesn't start soon, it's good. That's because we have a > time to activate it and > when reclaim happens, reclaimer can reclaim pages easily. > > If I don't understand your point, could you elaborate on it? If reclaim doesn't happen soon and the page was dirty or under writeback (and hence unreclaimable) then there's a better chance that it _will_ be reclaimable by the time reclaim comes along and has a look at it. Yes, that's good. And a note to Mel: this is one way in which we can get significant (perhaps tremendous) numbers of dirty pages coming off the tail of the LRU, and hence eligible for pageout() treatment. -- 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/