From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id E21AD8D0039 for ; Thu, 10 Feb 2011 16:01:11 -0500 (EST) Date: Thu, 10 Feb 2011 13:00:37 -0800 From: Andrew Morton Subject: Re: [PATCH] mm: batch-free pcp list if possible Message-Id: <20110210130037.24dbde41.akpm@linux-foundation.org> In-Reply-To: <20110210093544.GA17873@csn.ul.ie> References: <1297257677-12287-1-git-send-email-namhyung@gmail.com> <20110209123803.4bb6291c.akpm@linux-foundation.org> <20110210093544.GA17873@csn.ul.ie> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Namhyung Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Johannes Weiner On Thu, 10 Feb 2011 09:35:44 +0000 Mel Gorman wrote: > > What's the point in that? What relationship does the number of > > contiguous empty lists have with the number of pages to free from one > > list? > > > > The point is to avoid excessive checking of empty lists. It seems pretty simple to me to skip the testing of empty lists altogether. I suggested one way, however I suspect a better approach might be to maintain a count of the number of pages in each list and then change free_pcppages_bulk() so that it calculates up-front the number of pages to free from each list (equal proportion of each) then sits in a tight loop freeing that number of pages. It might be that the overhead of maintaining the per-list count makes that not worthwhile. It'll be hard to tell because the count maintenance cost will be smeared all over the place. I doubt if any of it matters much, compared to the cost of allocating, populating and freeing a page. I just want free_pcppages_bulk() to stop hurting my brain ;) -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org