Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752955AbaBMHB3 (ORCPT ); Thu, 13 Feb 2014 02:01:29 -0500 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:38936 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752506AbaBMHB1 (ORCPT ); Thu, 13 Feb 2014 02:01:27 -0500 Message-ID: <52FC6F2A.30905@linux.vnet.ibm.com> Date: Thu, 13 Feb 2014 12:37:22 +0530 From: Raghavendra K T Organization: IBM User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: David Rientjes CC: Andrew Morton , Fengguang Wu , David Cohen , Al Viro , Damien Ramonda , Jan Kara , Linus Torvalds , 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 References: <1390388025-1418-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> <20140206145105.27dec37b16f24e4ac5fd90ce@linux-foundation.org> <20140206152219.45c2039e5092c8ea1c31fd38@linux-foundation.org> <52F4B8A4.70405@linux.vnet.ibm.com> <52F88C16.70204@linux.vnet.ibm.com> <52F8C556.6090006@linux.vnet.ibm.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14021307-1396-0000-0000-00000448E0B4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/11/2014 03:05 AM, David Rientjes wrote: > On Mon, 10 Feb 2014, Raghavendra K T wrote: > >> So I understood that you are suggesting implementations like below >> >> 1) I do not have problem with the below approach, I could post this in >> next version. >> ( But this did not include 4k limit Linus mentioned to apply) >> >> unsigned long max_sane_readahead(unsigned long nr) >> { >> unsigned long local_free_page; >> int nid; >> >> nid = numa_mem_id(); >> >> /* >> * We sanitize readahead size depending on free memory in >> * the local node. >> */ >> local_free_page = node_page_state(nid, NR_INACTIVE_FILE) >> + node_page_state(nid, NR_FREE_PAGES); >> return min(nr, local_free_page / 2); >> } >> >> 2) I did not go for below because Honza (Jan Kara) had some >> concerns for 4k limit for normal case, and since I am not >> the expert, I was waiting for opinions. >> >> unsigned long max_sane_readahead(unsigned long nr) >> { >> unsigned long local_free_page, sane_nr; >> int nid; >> >> nid = numa_mem_id(); >> /* limit the max readahead to 4k pages */ >> sane_nr = min(nr, MAX_REMOTE_READAHEAD); >> >> /* >> * We sanitize readahead size depending on free memory in >> * the local node. >> */ >> local_free_page = node_page_state(nid, NR_INACTIVE_FILE) >> + node_page_state(nid, NR_FREE_PAGES); >> return min(sane_nr, local_free_page / 2); >> } >> > > I have no opinion on the 4KB pages, either of the above is just fine. > I was able to test (1) implementation on the system where readahead problem occurred. Unfortunately it did not help. Reason seem to be that CONFIG_HAVE_MEMORYLESS_NODES dependency of numa_mem_id(). The PPC machine I am facing problem has topology like this: numactl -H --------- available: 2 nodes (0-1) node 0 cpus: 0 1 2 3 4 5 6 7 12 13 14 15 16 17 18 19 20 21 22 23 24 25 ... node 0 size: 0 MB node 0 free: 0 MB node 1 cpus: 8 9 10 11 32 33 34 35 ... node 1 size: 8071 MB node 1 free: 2479 MB node distances: node 0 1 0: 10 20 1: 20 10 So it seems numa_mem_id() does not help for all the configs.. Am I missing something ? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/