Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755860Ab1EIDVS (ORCPT ); Sun, 8 May 2011 23:21:18 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:39760 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750818Ab1EIDVR (ORCPT ); Sun, 8 May 2011 23:21:17 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: Minchan Kim Subject: Re: [RFC 6/8] In order putback lru core Cc: kosaki.motohiro@jp.fujitsu.com, Mel Gorman , Andrew Morton , linux-mm , LKML , Christoph Lameter , Johannes Weiner , KAMEZAWA Hiroyuki , Rik van Riel , Andrea Arcangeli In-Reply-To: References: <20110501224844.75EC.A69D9226@jp.fujitsu.com> Message-Id: <20110509122255.3AD5.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Mailer: Becky! ver. 2.56.05 [ja] Date: Mon, 9 May 2011 12:21:11 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3145 Lines: 82 > On Sun, May 1, 2011 at 10:47 PM, KOSAKI Motohiro > wrote: > >> > +/* This structure is used for keeping LRU ordering of isolated page */ > >> > +struct pages_lru { > >> > +        struct page *page;      /* isolated page */ > >> > +        struct page *prev_page; /* previous page of isolate page as LRU order */ > >> > +        struct page *next_page; /* next page of isolate page as LRU order */ > >> > +        struct list_head lru; > >> > +}; > >> >  /* > >> > >> So this thing has to be allocated from somewhere. We can't put it > >> on the stack as we're already in danger there so we must be using > >> kmalloc. In the reclaim paths, this should be avoided obviously. > >> For compaction, we might hurt the compaction success rates if pages > >> are pinned with control structures. It's something to be wary of. > >> > >> At LSF/MM, I stated a preference for swapping the source and > >> destination pages in the LRU. This unfortunately means that the LRU > >> now contains a page in the process of being migrated to and the backout > >> paths for migration failure become a lot more complex. Reclaim should > >> be ok as it'll should fail to lock the page and recycle it in the list. > >> This avoids allocations but I freely admit that I'm not in the position > >> to implement such a thing right now :( > > > > I like swaping to fake page. one way pointer might become dangerous. vmscan can > > detect fake page and ignore it. > > > I guess it means swapping between migrated-from page and migrated-to page. > Right? no. I was intend to use fake struct page. but this idea is also good to me. > If so, migrated-from page is already removed from LRU list and > migrated-to page isn't LRU as it's page allocated newly so they don't > have any LRU information. How can we swap them? We need space keeps > LRU information before removing the page from LRU list. :( pure fake struct page or preallocation migrated-to page? > > Could you explain in detail about swapping if I miss something? > > About one way pointer, I think it's no problem. Worst case I imagine > is to put the page in head of LRU list. It means it's same issue now. > So it doesn't make worse than now. > > > > > ie, > > is_fake_page(page) > > { > >        if (is_stack_addr((void*)page)) > >                return true; > >        return false; > > } > > > > Also, I like to use stack rather than kmalloc in compaction. > > > > Compaction is a procedure of reclaim. As you know, we had a problem > about using of stack during reclaim path. > I admit kmalloc-thing isn't good. > I will try to solve the issue as TODO. It depend on stack consumption size. because we don't call pageout() from compaction path. It's big different from regular reclaim path. > > Thanks for the review, KOSAKI. Yeah, thank you for making very good patch! -- 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/