From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f198.google.com (mail-wr0-f198.google.com [209.85.128.198]) by kanga.kvack.org (Postfix) with ESMTP id D12CA6B025F for ; Mon, 20 Nov 2017 20:04:32 -0500 (EST) Received: by mail-wr0-f198.google.com with SMTP id d14so7046268wrg.15 for ; Mon, 20 Nov 2017 17:04:32 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id p10si9422107wrf.530.2017.11.20.17.04.31 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 20 Nov 2017 17:04:31 -0800 (PST) Date: Mon, 20 Nov 2017 17:04:29 -0800 From: Andrew Morton Subject: Re: [PATCH] mm, meminit: Serially initialise deferred memory if trace_buf_size is specified Message-Id: <20171120170429.315726fb004905314ced614e@linux-foundation.org> In-Reply-To: References: <20171115085556.fla7upm3nkydlflp@techsingularity.net> <20171115115559.rjb5hy6d6332jgjj@dhcp22.suse.cz> <20171115141329.ieoqvyoavmv6gnea@techsingularity.net> <20171115142816.zxdgkad3ch2bih6d@dhcp22.suse.cz> <20171115144314.xwdi2sbcn6m6lqdo@techsingularity.net> <20171115145716.w34jaez5ljb3fssn@dhcp22.suse.cz> <06a33f82-7f83-7721-50ec-87bf1370c3d4@gmail.com> <20171116085433.qmz4w3y3ra42j2ih@dhcp22.suse.cz> <20171116100633.moui6zu33ctzpjsf@techsingularity.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Pavel Tatashin Cc: Mel Gorman , Michal Hocko , YASUAKI ISHIMATSU , Linux Memory Management List , linux-kernel@vger.kernel.org, koki.sanagi@us.fujitsu.com, Steve Sistare On Fri, 17 Nov 2017 13:19:56 -0500 Pavel Tatashin wrote: > On Thu, Nov 16, 2017 at 5:06 AM, Mel Gorman wrote: > > 4. Put a check into the page allocator slowpath that triggers serialised > > init if the system is booting and an allocation is about to fail. It > > would be such a cold path that it would never be noticable although it > > would leave dead code in the kernel image once boot had completed > > Hi Mel, > > The forth approach is the best as it is seamless for admins and > engineers, it will also work on any system configuration with any > parameters without any special involvement. Apart from what-mel-said, I'd be concerned that this failsafe would almost never get tested. We should find some way to ensure that this code gets exercised in some people's kernels on a permanent basis and I'm not sure how to do that. One option might be to ask Fengguang to add the occasional test_pavels_stuff=1 to the kernel boot commandline. That's better than nothing but 0-day only runs on a small number of machine types. -- 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