From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f172.google.com (mail-pd0-f172.google.com [209.85.192.172]) by kanga.kvack.org (Postfix) with ESMTP id 334066B0038 for ; Mon, 30 Mar 2015 01:35:11 -0400 (EDT) Received: by pdnc3 with SMTP id c3so164695901pdn.0 for ; Sun, 29 Mar 2015 22:35:10 -0700 (PDT) Received: from mail-pd0-x22a.google.com (mail-pd0-x22a.google.com. [2607:f8b0:400e:c02::22a]) by mx.google.com with ESMTPS id g4si13233496pdd.111.2015.03.29.22.35.10 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 29 Mar 2015 22:35:10 -0700 (PDT) Received: by pdnc3 with SMTP id c3so164695487pdn.0 for ; Sun, 29 Mar 2015 22:35:10 -0700 (PDT) Date: Mon, 30 Mar 2015 14:35:02 +0900 From: Minchan Kim Subject: Re: [PATCH 3/4] mm: move lazy free pages to inactive list Message-ID: <20150330053502.GB3008@blaptop> References: <1426036838-18154-1-git-send-email-minchan@kernel.org> <1426036838-18154-3-git-send-email-minchan@kernel.org> <20150320154358.51bcf3cbceeb8fbbdb2b58e5@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150320154358.51bcf3cbceeb8fbbdb2b58e5@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Johannes Weiner , Mel Gorman , Rik van Riel , Shaohua Li , Yalin.Wang@sonymobile.com Hello Andrew, On Fri, Mar 20, 2015 at 03:43:58PM -0700, Andrew Morton wrote: > On Wed, 11 Mar 2015 10:20:37 +0900 Minchan Kim wrote: > > > MADV_FREE is hint that it's okay to discard pages if there is > > memory pressure and we uses reclaimers(ie, kswapd and direct reclaim) > > to free them so there is no worth to remain them in active anonymous LRU > > so this patch moves them to inactive LRU list's head. > > > > This means that MADV_FREE-ed pages which were living on the inactive list > > are reclaimed first because they are more likely to be cold rather than > > recently active pages. > > > > A arguable issue for the approach would be whether we should put it to > > head or tail in inactive list. I selected *head* because kernel cannot > > make sure it's really cold or warm for every MADV_FREE usecase but > > at least we know it's not *hot* so landing of inactive head would be > > comprimise for various usecases. > > > > This is fixing a suboptimal behavior of MADV_FREE when pages living on > > the active list will sit there for a long time even under memory > > pressure while the inactive list is reclaimed heavily. This basically > > breaks the whole purpose of using MADV_FREE to help the system to free > > memory which is might not be used. > > > > @@ -789,6 +790,23 @@ static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec, > > update_page_reclaim_stat(lruvec, file, 0); > > } > > > > + > > +static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec, > > + void *arg) > > > > ... > > > > @@ -844,6 +866,18 @@ void deactivate_file_page(struct page *page) > > } > > } > > > > +void deactivate_page(struct page *page) > > +{ > > lru_deactivate_file_fn() and deactivate_file_page() are carefully > documented and lru_deactivate_fn() and deactivate_page() should > be as well. In fact it becomes more important now that we have two > similar-looking things. Sorry, I have missed this comment. Acutally, deactive_file_page was too specific on file-backed page invalidation when I implemented first time. That's why it had a lot description but deactivate_page is too general so I think short comment is enough. :) Here it goes. Thanks.