From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753230Ab3LQLUN (ORCPT ); Tue, 17 Dec 2013 06:20:13 -0500 Received: from cantor2.suse.de ([195.135.220.15]:52258 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751853Ab3LQLUL (ORCPT ); Tue, 17 Dec 2013 06:20:11 -0500 Date: Tue, 17 Dec 2013 11:20:07 +0000 From: Mel Gorman To: Johannes Weiner Cc: Andrew Morton , Dave Hansen , Rik van Riel , Linux-MM , LKML Subject: Re: [PATCH 6/7] mm: page_alloc: Only account batch allocations requests that are eligible Message-ID: <20131217112007.GA11295@suse.de> References: <1386943807-29601-1-git-send-email-mgorman@suse.de> <1386943807-29601-7-git-send-email-mgorman@suse.de> <20131216205237.GB21724@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20131216205237.GB21724@cmpxchg.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 16, 2013 at 03:52:37PM -0500, Johannes Weiner wrote: > On Fri, Dec 13, 2013 at 02:10:06PM +0000, Mel Gorman wrote: > > Not signed off. Johannes, was the intent really to decrement the batch > > counts regardless of whether the policy was being enforced or not? > > Yes. Bursts of allocations for which the policy does not get enforced > will still create memory pressure and affect cache aging on a given > node. So even if we only distribute page cache, we want to distribute > it in a way that all allocations on the eligible zones equal out. This means that allocations for page table pages affects the distribution of page cache pages. An adverse workload could time when it faults anonymous pages (to allocate anon and page table pages) in batch sequences and then access files to force page cache pages to be allocated from a single node. I think I know what your response will be. It will be that the utilisation of the zone for page table pages and anon pages means that you want more page cache pages to be allocated from the other zones so the reclaim pressure is still more or less even. If this is the case or there is another reason then it could have done with a comment because it's a subtle detail. -- Mel Gorman SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ea0-f171.google.com (mail-ea0-f171.google.com [209.85.215.171]) by kanga.kvack.org (Postfix) with ESMTP id 7B32E6B0035 for ; Tue, 17 Dec 2013 06:20:11 -0500 (EST) Received: by mail-ea0-f171.google.com with SMTP id h10so2793400eak.16 for ; Tue, 17 Dec 2013 03:20:11 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id a9si4920392eew.138.2013.12.17.03.20.10 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 17 Dec 2013 03:20:10 -0800 (PST) Date: Tue, 17 Dec 2013 11:20:07 +0000 From: Mel Gorman Subject: Re: [PATCH 6/7] mm: page_alloc: Only account batch allocations requests that are eligible Message-ID: <20131217112007.GA11295@suse.de> References: <1386943807-29601-1-git-send-email-mgorman@suse.de> <1386943807-29601-7-git-send-email-mgorman@suse.de> <20131216205237.GB21724@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20131216205237.GB21724@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: Andrew Morton , Dave Hansen , Rik van Riel , Linux-MM , LKML On Mon, Dec 16, 2013 at 03:52:37PM -0500, Johannes Weiner wrote: > On Fri, Dec 13, 2013 at 02:10:06PM +0000, Mel Gorman wrote: > > Not signed off. Johannes, was the intent really to decrement the batch > > counts regardless of whether the policy was being enforced or not? > > Yes. Bursts of allocations for which the policy does not get enforced > will still create memory pressure and affect cache aging on a given > node. So even if we only distribute page cache, we want to distribute > it in a way that all allocations on the eligible zones equal out. This means that allocations for page table pages affects the distribution of page cache pages. An adverse workload could time when it faults anonymous pages (to allocate anon and page table pages) in batch sequences and then access files to force page cache pages to be allocated from a single node. I think I know what your response will be. It will be that the utilisation of the zone for page table pages and anon pages means that you want more page cache pages to be allocated from the other zones so the reclaim pressure is still more or less even. If this is the case or there is another reason then it could have done with a comment because it's a subtle detail. -- Mel Gorman SUSE Labs -- 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