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=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 94671C432C3 for ; Thu, 11 Mar 2021 16:41:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C88864FE9 for ; Thu, 11 Mar 2021 16:41:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229814AbhCKQlY (ORCPT ); Thu, 11 Mar 2021 11:41:24 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:21972 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229606AbhCKQlN (ORCPT ); Thu, 11 Mar 2021 11:41:13 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615480873; 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=GkBT2/QcrP06DnXp9UhFQvFFWxYG4lqLjwld1F9Zqa0=; b=RB/44mUogC9h3oib6tmQWbF+QHqSyV9+yQm821zyiJj7Qv2qxkoLAXW/aiDP2XJTwL4KmC 4eBbqQ4HNzdm8uz/KLwelzvOSeyEc4ibSlO61pitA3X/8KVrLU2Y5zAx6NuSOxVGzGTn34 rO4gE6fVGU764BrXkUI5DRC7+f+IqTY= 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-392-xJ9ALbmLNk2YfcormWPl-A-1; Thu, 11 Mar 2021 11:41:09 -0500 X-MC-Unique: xJ9ALbmLNk2YfcormWPl-A-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 6ABD88EC1A8; Thu, 11 Mar 2021 16:40:37 +0000 (UTC) Received: from [10.36.115.26] (ovpn-115-26.ams2.redhat.com [10.36.115.26]) by smtp.corp.redhat.com (Postfix) with ESMTP id D0B3C60BE5; Thu, 11 Mar 2021 16:40:35 +0000 (UTC) Subject: Re: [PATCH v3] mm: page_alloc: dump migrate-failed pages To: Minchan Kim , Andrew Morton Cc: linux-mm , LKML , John Dias , Michal Hocko , Jason Baron References: <20210310180104.517886-1-minchan@kernel.org> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Thu, 11 Mar 2021 17:40:35 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <20210310180104.517886-1-minchan@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10.03.21 19:01, Minchan Kim wrote: > Currently, debugging CMA allocation failures is quite limited. > The most commong source of these failures seems to be page > migration which doesn't provide any useful information on the > reason of the failure by itself. alloc_contig_range can report > those failures as it holds a list of migrate-failed pages. > > page refcount, mapcount with page flags on dump_page are > helpful information to deduce the culprit. Furthermore, > dump_page_owner was super helpful to find long term pinner > who initiated the page allocation. > > The reason it approach with dynamic debug is the debug message > could emit lots of noises as alloc_contig_range calls more > frequently since it's a best effort allocator. > > There are two ifdefery conditions to support common dyndbg options: > > - CONFIG_DYNAMIC_DEBUG_CORE && DYNAMIC_DEBUG_MODULE > It aims for supporting the feature with only specific file > with adding ccflags. > > - CONFIG_DYNAMIC_DEBUG > It aims for supporting the feature with system wide globally. > > A simple example to enable the feature: > > Admin could enable the dump like this(by default, disabled) > > echo "func dump_migrate_failure_pages +p" > control > > Admin could disable it. > > echo "func dump_migrate_failure_pages =_" > control > > Detail goes Documentation/admin-guide/dynamic-debug-howto.rst > > A concern is utility functions in dump_page uses inconsistent > loglevels. > > __dump_page: KERN_WARNING > __dump_page_owner: KERN_ALERT > stack_trace_print: KERN_DEFAULT > > There are bunch of places to use the inconsistent loglevel > utility functions(e.g., just grep dump_page/strace_trace_print). > It's unfortunate but here we are. It could be addressed > different patchset. > > Signed-off-by: Minchan Kim > --- > * from v2 - https://lore.kernel.org/linux-mm/20210308202047.1903802-1-minchan@kernel.org/ > * remove ratelimit - mhocko > > * from v1 - https://lore.kernel.org/linux-mm/20210217163603.429062-1-minchan@kernel.org/ > * use dynamic debugging with system wide instead of per-call site - mhocko > > mm/page_alloc.c | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 3e4b29ee2b1e..f42f3e208794 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -8453,6 +8453,27 @@ static unsigned long pfn_max_align_up(unsigned long pfn) > pageblock_nr_pages)); > } > > +#if defined(CONFIG_DYNAMIC_DEBUG) || \ > + (defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE)) > +static void alloc_contig_dump_pages(struct list_head *page_list) > +{ > + DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, > + "migrate failure"); > + > + if (DYNAMIC_DEBUG_BRANCH(descriptor)) { > + struct page *page; > + > + WARN(1, "failed callstack"); Not sure if we want that here. You can deterministically crash a kernel with panic_on_warn set - which is what some distros already do. Some other way to dump the current call stack would be handy ... > + list_for_each_entry(page, page_list, lru) > + dump_page(page, "migration failure"); > + } > +} > +#else > +static inline void alloc_contig_dump_pages(struct list_head *page_list) > +{ > +} > +#endif > + > /* [start, end) must belong to a single zone. */ > static int __alloc_contig_migrate_range(struct compact_control *cc, > unsigned long start, unsigned long end) > @@ -8496,6 +8517,7 @@ static int __alloc_contig_migrate_range(struct compact_control *cc, > NULL, (unsigned long)&mtc, cc->mode, MR_CONTIG_RANGE); > } > if (ret < 0) { > + alloc_contig_dump_pages(&cc->migratepages); > putback_movable_pages(&cc->migratepages); > return ret; > } > For me, this is good enough for now. -- Thanks, David / dhildenb