From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f179.google.com (mail-pd0-f179.google.com [209.85.192.179]) by kanga.kvack.org (Postfix) with ESMTP id 015396B0038 for ; Fri, 6 Dec 2013 03:50:54 -0500 (EST) Received: by mail-pd0-f179.google.com with SMTP id r10so660315pdi.24 for ; Fri, 06 Dec 2013 00:50:54 -0800 (PST) Received: from LGEMRELSE6Q.lge.com (LGEMRELSE6Q.lge.com. [156.147.1.121]) by mx.google.com with ESMTP id bc2si60602442pad.187.2013.12.06.00.50.52 for ; Fri, 06 Dec 2013 00:50:53 -0800 (PST) Date: Fri, 6 Dec 2013 17:53:31 +0900 From: Joonsoo Kim Subject: [QUESTION] balloon page isolation needs LRU lock? Message-ID: <20131206085331.GA24706@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: Rafael Aquini Cc: Mel Gorman , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Hello, Rafael. I looked at some compaction code and found that some oddity about balloon compaction. In isolate_migratepages_range(), if we meet !PageLRU(), we check whether this page is for balloon compaction. In this case, code needs locked. Is the lock really needed? I can't find any relationship between balloon compaction and LRU lock. Second question is that in above case if we don't hold a lock, we skip this page. I guess that if we meet balloon page repeatedly, there is no change to run isolation. Am I missing? Please let me know what I am missing. Thanks in advance. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756999Ab3LFIu5 (ORCPT ); Fri, 6 Dec 2013 03:50:57 -0500 Received: from LGEMRELSE6Q.lge.com ([156.147.1.121]:61284 "EHLO LGEMRELSE6Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753205Ab3LFIux (ORCPT ); Fri, 6 Dec 2013 03:50:53 -0500 X-AuditID: 9c930179-b7ce4ae000000e86-bc-52a18feb60e1 Date: Fri, 6 Dec 2013 17:53:31 +0900 From: Joonsoo Kim To: Rafael Aquini Cc: Mel Gorman , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [QUESTION] balloon page isolation needs LRU lock? Message-ID: <20131206085331.GA24706@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Rafael. I looked at some compaction code and found that some oddity about balloon compaction. In isolate_migratepages_range(), if we meet !PageLRU(), we check whether this page is for balloon compaction. In this case, code needs locked. Is the lock really needed? I can't find any relationship between balloon compaction and LRU lock. Second question is that in above case if we don't hold a lock, we skip this page. I guess that if we meet balloon page repeatedly, there is no change to run isolation. Am I missing? Please let me know what I am missing. Thanks in advance.