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=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 41296C433E9 for ; Thu, 18 Feb 2021 18:45:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 10AE364EC0 for ; Thu, 18 Feb 2021 18:45:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232489AbhBRSpB (ORCPT ); Thu, 18 Feb 2021 13:45:01 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:52802 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232798AbhBRQ1p (ORCPT ); Thu, 18 Feb 2021 11:27:45 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613665576; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=J2X67q8itB+nQRLaZpwWTEn/d/SF56gQm3JBUDCWd+8=; b=R1ZFnnXnzMrdgteI4mjCPxlH3Zi6EUjzyd27BUgxLWKaA3WndEA0QVICelcGLAVundm90V smCv4Tl8XXDXVODq89W8qL6HVC/cbzArsjVo8xF33u2sVQd8UGlNX2r2W6kpBtuu8XQZ6l VcNRnW3MLzBvFgH/aeHIH5rt4mwwUYU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-519-HfbNI61sPhqZboRszWpnDQ-1; Thu, 18 Feb 2021 11:26:12 -0500 X-MC-Unique: HfbNI61sPhqZboRszWpnDQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A170F874983; Thu, 18 Feb 2021 16:26:10 +0000 (UTC) Received: from [10.36.114.59] (ovpn-114-59.ams2.redhat.com [10.36.114.59]) by smtp.corp.redhat.com (Postfix) with ESMTP id 286F360C6B; Thu, 18 Feb 2021 16:26:08 +0000 (UTC) To: Minchan Kim Cc: Michal Hocko , Andrew Morton , linux-mm , LKML , joaodias@google.com References: <20210217163603.429062-1-minchan@kernel.org> <2f167b3c-5f0a-444a-c627-49181fc8fe0d@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [PATCH] mm: be more verbose for alloc_contig_range faliures Message-ID: Date: Thu, 18 Feb 2021 17:26:08 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18.02.21 17:19, Minchan Kim wrote: > On Thu, Feb 18, 2021 at 10:43:21AM +0100, David Hildenbrand wrote: >> On 18.02.21 10:35, Michal Hocko wrote: >>> On Thu 18-02-21 10:02:43, David Hildenbrand wrote: >>>> On 18.02.21 09:56, Michal Hocko wrote: >>>>> On Wed 17-02-21 08:36:03, Minchan Kim wrote: >>>>>> alloc_contig_range is usually used on cma area or movable zone. >>>>>> It's critical if the page migration fails on those areas so >>>>>> dump more debugging message like memory_hotplug unless user >>>>>> specifiy __GFP_NOWARN. >>>>> >>>>> I agree with David that this has a potential to generate a lot of output >>>>> and it is not really clear whether it is worth it. Page isolation code >>>>> already has REPORT_FAILURE mode which currently used only for the memory >>>>> hotplug because this was just too noisy from the CMA path - d381c54760dc >>>>> ("mm: only report isolation failures when offlining memory"). >>>>> >>>>> Maybe migration failures are less likely to fail but still. >>>> >>>> Side note: I really dislike that uncontrolled error reporting on memory >>>> offlining path we have enabled as default. Yeah, it might be useful for >>>> ZONE_MOVABLE in some cases, but otherwise it's just noise. >>>> >>>> Just do a "sudo stress-ng --memhotplug 1" and see the log getting flooded >>> >>> Anyway we can discuss this in a separate thread but I think this is not >>> a representative workload. >> >> Sure, but the essence is "this is noise", and we'll have more noise on >> alloc_contig_range() as we see these calls more frequently. There should be >> an explicit way to enable such *debug* messages. > > alloc_contig_range already has gfp_mask and it respects __GFP_NOWARN. I am not 100% sure it does. > Why shouldn't people use it if they don't care the failure? Because flooding the log with noise maybe a handful of people on this planet care about is absolutely useless. With the warnings in warn_alloc() people can at least conclude something reasonable. > Semantically, it makes sense to me. > > About the messeage flooding, shouldn't we go with ratelimiting? At least that (see warn_alloc()). But I'd even want to see some other trigger to enable this explicitly on demand. -- Thanks, David / dhildenb