From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751898AbaBFX6W (ORCPT ); Thu, 6 Feb 2014 18:58:22 -0500 Received: from mail-pd0-f170.google.com ([209.85.192.170]:59258 "EHLO mail-pd0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751077AbaBFX6T (ORCPT ); Thu, 6 Feb 2014 18:58:19 -0500 Date: Thu, 6 Feb 2014 15:58:17 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Andrew Morton cc: Raghavendra K T , Fengguang Wu , David Cohen , Al Viro , Damien Ramonda , Jan Kara , Linus , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH V5] mm readahead: Fix readahead fail for no local memory and limit readahead pages In-Reply-To: Message-ID: References: <1390388025-1418-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> <20140206145105.27dec37b16f24e4ac5fd90ce@linux-foundation.org> <20140206152219.45c2039e5092c8ea1c31fd38@linux-foundation.org> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 6 Feb 2014, David Rientjes wrote: > > > > > +#define MAX_REMOTE_READAHEAD 4096UL > Normally it wouldn't matter because there's no significant downside to it > racing, things like mempolicies which use numa_node_id() extensively would > result in, oops, a page allocation on the wrong node. > > This stands out to me, though, because you're expecting the calculation to > be correct for a specific node. > > The patch is still wrong, though, it should just do > > int node = ACCESS_ONCE(numa_mem_id()); > return min(nr, (node_page_state(node, NR_INACTIVE_FILE) + > node_page_state(node, NR_FREE_PAGES)) / 2); > > since we want to readahead based on the cpu's local node, the comment > saying we're reading ahead onto "remote memory" is wrong since a > memoryless node has local affinity to numa_mem_id(). > Oops, forgot about the MAX_REMOTE_READAHEAD which needs to be factored in as well, but this handles the bound on local node's statistics. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f175.google.com (mail-pd0-f175.google.com [209.85.192.175]) by kanga.kvack.org (Postfix) with ESMTP id 621A96B0035 for ; Thu, 6 Feb 2014 18:58:21 -0500 (EST) Received: by mail-pd0-f175.google.com with SMTP id w10so2363461pde.6 for ; Thu, 06 Feb 2014 15:58:21 -0800 (PST) Received: from mail-pb0-x229.google.com (mail-pb0-x229.google.com [2607:f8b0:400e:c01::229]) by mx.google.com with ESMTPS id if4si2789735pbc.16.2014.02.06.15.58.19 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 06 Feb 2014 15:58:19 -0800 (PST) Received: by mail-pb0-f41.google.com with SMTP id up15so2461521pbc.28 for ; Thu, 06 Feb 2014 15:58:19 -0800 (PST) Date: Thu, 6 Feb 2014 15:58:17 -0800 (PST) From: David Rientjes Subject: Re: [RFC PATCH V5] mm readahead: Fix readahead fail for no local memory and limit readahead pages In-Reply-To: Message-ID: References: <1390388025-1418-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> <20140206145105.27dec37b16f24e4ac5fd90ce@linux-foundation.org> <20140206152219.45c2039e5092c8ea1c31fd38@linux-foundation.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Raghavendra K T , Fengguang Wu , David Cohen , Al Viro , Damien Ramonda , Jan Kara , Linus , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Thu, 6 Feb 2014, David Rientjes wrote: > > > > > +#define MAX_REMOTE_READAHEAD 4096UL > Normally it wouldn't matter because there's no significant downside to it > racing, things like mempolicies which use numa_node_id() extensively would > result in, oops, a page allocation on the wrong node. > > This stands out to me, though, because you're expecting the calculation to > be correct for a specific node. > > The patch is still wrong, though, it should just do > > int node = ACCESS_ONCE(numa_mem_id()); > return min(nr, (node_page_state(node, NR_INACTIVE_FILE) + > node_page_state(node, NR_FREE_PAGES)) / 2); > > since we want to readahead based on the cpu's local node, the comment > saying we're reading ahead onto "remote memory" is wrong since a > memoryless node has local affinity to numa_mem_id(). > Oops, forgot about the MAX_REMOTE_READAHEAD which needs to be factored in as well, but this handles the bound on local node's statistics. -- 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