Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752678Ab1BNJZh (ORCPT ); Mon, 14 Feb 2011 04:25:37 -0500 Received: from e28smtp05.in.ibm.com ([122.248.162.5]:53457 "EHLO e28smtp05.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751847Ab1BNJZe (ORCPT ); Mon, 14 Feb 2011 04:25:34 -0500 Date: Sun, 13 Feb 2011 23:03:36 +0530 From: Balbir Singh To: Minchan Kim Cc: linux-mm@kvack.org, akpm@linux-foundation.org, npiggin@kernel.dk, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, kosaki.motohiro@jp.fujitsu.com, cl@linux.com, kamezawa.hiroyu@jp.fujitsu.com Subject: Re: [PATCH 3/3] Provide control over unmapped pages (v4) Message-ID: <20110213173336.GC23919@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20110125051003.13762.35120.stgit@localhost6.localdomain6> <20110125051015.13762.13429.stgit@localhost6.localdomain6> <20110128064851.GB5054@balbir.in.ibm.com> <20110128111833.GD5054@balbir.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2819 Lines: 77 * MinChan Kim [2011-02-10 14:41:44]: > I don't know why the part of message is deleted only when I send you. > Maybe it's gmail bug. > > I hope mail sending is successful in this turn. :) > > On Thu, Feb 10, 2011 at 2:33 PM, Minchan Kim wrote: > > Sorry for late response. > > > > On Fri, Jan 28, 2011 at 8:18 PM, Balbir Singh wrote: > >> * MinChan Kim [2011-01-28 16:24:19]: > >> > >>> > > >>> > But the assumption for LRU order to change happens only if the page > >>> > cannot be successfully freed, which means it is in some way active.. > >>> > and needs to be moved no? > >>> > >>> 1. holded page by someone > >>> 2. mapped pages > >>> 3. active pages > >>> > >>> 1 is rare so it isn't the problem. > >>> Of course, in case of 3, we have to activate it so no problem. > >>> The problem is 2. > >>> > >> > >> 2 is a problem, but due to the size aspects not a big one. Like you > >> said even lumpy reclaim affects it. May be the reclaim code could > >> honour may_unmap much earlier. > > > > Even if it is, it's a trade-off to get a big contiguous memory. I > > don't want to add new mess. (In addition, lumpy is weak by compaction > > as time goes by) > > What I have in mind for preventing LRU ignore is that put the page > > into original position instead of head of lru. Maybe it can help the > > situation both lumpy and your case. But it's another story. > > > > How about the idea? > > > > I borrow the idea from CFLRU[1] > > - PCFLRU(Page-Cache First LRU) > > > > When we allocates new page for page cache, we adds the page into LRU's tail. > > When we map the page cache into page table, we rotate the page into LRU's head. > > > > So, inactive list's result is following as. > > > > M.P : mapped page > > N.P : none-mapped page > > > > HEAD-M.P-M.P-M.P-M.P-N.P-N.P-N.P-N.P-N.P-TAIL > > > > Admin can set threshold window size which determines stop reclaiming > > none-mapped page contiguously. > > > > I think it needs some tweak of page cache/page mapping functions but > > we can use kswapd/direct reclaim without change. > > > > Also, it can change page reclaim policy totally but it's just what you > > want, I think. > > I am not sure how this would work, moreover the idea behind min_unmapped_pages is to keep sufficient unmapped pages around for the FS metadata and has been working with the existing code for zone reclaim. What you propose is more drastic re-org of the LRU and I am not sure I have the apetite for it. -- Three Cheers, Balbir -- 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/