From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 88C61C28CF6 for ; Fri, 3 Aug 2018 03:22:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3ED1421711 for ; Fri, 3 Aug 2018 03:22:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3ED1421711 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727049AbeHCFQJ (ORCPT ); Fri, 3 Aug 2018 01:16:09 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:37282 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725972AbeHCFQJ (ORCPT ); Fri, 3 Aug 2018 01:16:09 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6B0D418A; Thu, 2 Aug 2018 20:21:55 -0700 (PDT) Received: from [192.168.100.241] (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6AE163F5BA; Thu, 2 Aug 2018 20:21:54 -0700 (PDT) Subject: Re: [RFC 1/2] slub: Avoid trying to allocate memory on offline nodes To: Michal Hocko Cc: linux-mm@kvack.org, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, vbabka@suse.cz, Punit.Agrawal@arm.com, Lorenzo.Pieralisi@arm.com, linux-arm-kernel@lists.infradead.org, bhelgaas@google.com, linux-kernel@vger.kernel.org References: <20180801200418.1325826-1-jeremy.linton@arm.com> <20180801200418.1325826-2-jeremy.linton@arm.com> <20180802091554.GE10808@dhcp22.suse.cz> From: Jeremy Linton Message-ID: Date: Thu, 2 Aug 2018 22:21:53 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180802091554.GE10808@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 08/02/2018 04:15 AM, Michal Hocko wrote: > On Wed 01-08-18 15:04:17, Jeremy Linton wrote: > [...] >> @@ -2519,6 +2519,8 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, >> if (unlikely(!node_match(page, searchnode))) { >> stat(s, ALLOC_NODE_MISMATCH); >> deactivate_slab(s, page, c->freelist, c); >> + if (!node_online(searchnode)) >> + node = NUMA_NO_NODE; >> goto new_slab; > > This is inherently racy. Numa node can get offline at any point after > you check it here. Making it race free would involve some sort of > locking and I am not really convinced this is a good idea. I spent some time looking/thinking about this, and i'm pretty sure its not creating any new problems. But OTOH, I think the node_online() check is probably a bit misleading as what we really want to assure is that node >> } >> } >> -- >> 2.14.3 >> >