Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751473Ab0KWGFl (ORCPT ); Tue, 23 Nov 2010 01:05:41 -0500 Received: from mail-iw0-f174.google.com ([209.85.214.174]:46722 "EHLO mail-iw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751057Ab0KWGFk convert rfc822-to-8bit (ORCPT ); Tue, 23 Nov 2010 01:05:40 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=CV3t4gbMLDafhFRjvhczFZWZp20AC9ROc//psROWVqjlywOlB3SFk8WRZ/9jBv53lC /J29aEj7TsM1uK7EAQ1KnMpyCThbDVmxmU5I1clE/8fYSgz/kNay4YcLLipmZXj+XMGD GRWvH+MMuL85EEIB4Bh0PdJsWzkuMDSrbrfbw= MIME-Version: 1.0 In-Reply-To: <20101122214814.36c209a6.akpm@linux-foundation.org> References: <20101122141449.9de58a2c.akpm@linux-foundation.org> <20101122210132.be9962c7.akpm@linux-foundation.org> <20101122212220.ae26d9a5.akpm@linux-foundation.org> <20101122214814.36c209a6.akpm@linux-foundation.org> Date: Tue, 23 Nov 2010 15:05:39 +0900 Message-ID: Subject: Re: [RFC 1/2] deactive invalidated pages From: Minchan Kim To: Andrew Morton Cc: linux-mm , LKML , Peter Zijlstra , Rik van Riel , KOSAKI Motohiro , Johannes Weiner , Nick Piggin , Mel Gorman Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3844 Lines: 98 On Tue, Nov 23, 2010 at 2:48 PM, Andrew Morton wrote: > 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! I see your point. And it's why I add it to head of inactive list. > >> > 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. > I think you agree my as-is approach. Right? Then, could you revert your fixlet? I will add additional description with your fix. -- Kind regards, Minchan Kim -- 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/