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=-10.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 660BBC2D0E4 for ; Fri, 27 Nov 2020 10:23:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9C468206CA for ; Fri, 27 Nov 2020 10:23:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="i/9Q0fzK" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9C468206CA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 890386B0068; Fri, 27 Nov 2020 05:23:25 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 841FA6B006C; Fri, 27 Nov 2020 05:23:25 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7567B6B006E; Fri, 27 Nov 2020 05:23:25 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0149.hostedemail.com [216.40.44.149]) by kanga.kvack.org (Postfix) with ESMTP id 5BDD66B0068 for ; Fri, 27 Nov 2020 05:23:25 -0500 (EST) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 230ED180AD806 for ; Fri, 27 Nov 2020 10:23:25 +0000 (UTC) X-FDA: 77529811170.15.card44_5b019a127387 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin15.hostedemail.com (Postfix) with ESMTP id 028A11814B0C1 for ; Fri, 27 Nov 2020 10:23:24 +0000 (UTC) X-HE-Tag: card44_5b019a127387 X-Filterd-Recvd-Size: 8947 Received: from m42-4.mailgun.net (m42-4.mailgun.net [69.72.42.4]) by imf20.hostedemail.com (Postfix) with ESMTP for ; Fri, 27 Nov 2020 10:23:23 +0000 (UTC) DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1606472604; h=Content-Transfer-Encoding: Content-Type: In-Reply-To: MIME-Version: Date: Message-ID: From: References: Cc: To: Subject: Sender; bh=pTvgsAS6HkL3E+7Da6nmoAIr+QDgJJpECeYO2T5JvoM=; b=i/9Q0fzKwKQgX8Ggf4tzYyR4jCp+vExqOIam7rCljpGcgfIl9e6gTUTYEPvoljv8KtH3NH/6 ivrKR73dB8QN5np4DRdGT48oKKNbAYNAV7QAiQ0c9IlKL3nldrG/8zOoqJVaYYdTK5j48QnU LltE5+Q+MZShW6bMgKdlVjIw2ek= X-Mailgun-Sending-Ip: 69.72.42.4 X-Mailgun-Sid: WyIwY2Q3OCIsICJsaW51eC1tbUBrdmFjay5vcmciLCAiYmU5ZTRhIl0= Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n10.prod.us-east-1.postgun.com with SMTP id 5fc0d398e9b708862275c750 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Fri, 27 Nov 2020 10:23:20 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 0847EC43461; Fri, 27 Nov 2020 10:23:20 +0000 (UTC) Received: from [192.168.29.110] (unknown [49.37.154.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: charante) by smtp.codeaurora.org (Postfix) with ESMTPSA id 76895C433C6; Fri, 27 Nov 2020 10:23:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 76895C433C6 Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=charante@codeaurora.org Subject: Re: [PATCH] mm: memory_hotplug: put migration failure information under DEBUG_VM To: Michal Hocko Cc: akpm@linux-foundation.org, david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "vinmenon@codeaurora.org" References: <1606140196-6053-1-git-send-email-charante@codeaurora.org> <20201123141354.GQ27488@dhcp22.suse.cz> <20201124074141.GR27488@dhcp22.suse.cz> <685882be-10d7-e313-cb6c-f3f45fc2dd08@codeaurora.org> <20201126091822.GG31550@dhcp22.suse.cz> From: Charan Teja Kalla Message-ID: Date: Fri, 27 Nov 2020 15:53:14 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <20201126091822.GG31550@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Thanks Michal!! On 11/26/2020 2:48 PM, Michal Hocko wrote: > On Wed 25-11-20 16:18:06, Charan Teja Kalla wrote: >> >> >> On 11/24/2020 1:11 PM, Michal Hocko wrote: >>> On Mon 23-11-20 20:40:40, Charan Teja Kalla wrote: >>>> >>>> Thanks Michal! >>>> On 11/23/2020 7:43 PM, Michal Hocko wrote: >>>>> On Mon 23-11-20 19:33:16, Charan Teja Reddy wrote: >>>>>> When the pages are failed to get isolate or migrate, the page owner >>>>>> information along with page info is dumped. If there are continuous >>>>>> failures in migration(say page is pinned) or isolation, the log buffer >>>>>> is simply getting flooded with the page owner information. As most of >>>>>> the times page info is sufficient to know the causes for failures of >>>>>> migration or isolation, place the page owner information under DEBUG_VM. >>>>> >>>>> I do not see why this path is any different from others that call >>>>> dump_page. Page owner can add a very valuable information to debug >>>>> the underlying reasons for failures here. It is an opt-in debugging >>>>> feature which needs to be enabled explicitly. So I would argue users >>>>> are ready to accept a lot of data in the kernel log. >>>> >>>> Just thinking how frequently failures can happen in those paths. In the >>>> memory hotplug path, we can flood the page owner logs just by making one >>>> page pinned. >>> >>> If you are operating on a movable zone then pages shouldn't be pinned >>> for unbound amount of time. Yeah there are some ways to break this >>> fundamental assumption but this is a bigger problem that needs a >>> solution. >>> >>>> Say If it is anonymous page, the page owner information >>>> shows is something like below, which is not really telling anything >>>> other than how the pinned page is allocated. >>> >>> Well you can tell an anonymous page from __dump_page, all right, but >>> this is not true universally. >>> >>>> page last allocated via order 0, migratetype Movable, gfp_mask >>>> 0x100dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO) >>>> prep_new_page+0x7c/0x1a4 >>>> get_page_from_freelist+0x1ac/0x1c4 >>>> __alloc_pages_nodemask+0x12c/0x378 >>>> do_anonymous_page+0xac/0x3b4 >>>> handle_pte_fault+0x2a4/0x3bc >>>> __handle_speculative_fault+0x208/0x3c0 >>>> do_page_fault+0x280/0x508 >>>> do_translation_fault+0x3c/0x54 >>>> do_mem_abort+0x64/0xf4 >>>> el0_da+0x1c/0x20 >>>> page last free stack trace: >>>> free_pcp_prepare+0x320/0x454 >>>> free_unref_page_list+0x9c/0x2a4 >>>> release_pages+0x370/0x3c8 >>>> free_pages_and_swap_cache+0xdc/0x10c >>>> tlb_flush_mmu+0x110/0x134 >>>> tlb_finish_mmu+0x48/0xc0 >>>> unmap_region+0x104/0x138 >>>> __do_munmap+0x2ec/0x3b4 >>>> __arm64_sys_munmap+0x80/0xd8 >>>> >>>> I see at some places in the kernel where they put the dump_page under >>>> DEBUG_VM, but in the end I agree that it is up to the users need. Then >>>> there are some users who don't care for these page owner logs. >>> >>> Well, as I've said page_owner requires an explicit enabling and I would >>> expect that if somebody enables this tracking then it is expected to see >>> the information when we dump a page state. >>> >>>> And an issue on Embedded systems with these continuous logs being >>>> printed to the console is the watchdog timeouts, because console logging >>>> happens by disabling the interrupts. >>> >>> Are you enabling page_owner on those systems unconditionally? >>> >> >> Yes, We do always enable the page owner on just the internal debug >> builds for memory analysis, But never on the production kernels. And on >> these builds excessive logging, at times because of a pinned page, >> causing the watchdog timeouts, is the problem. > > OK, I see but I still believe that the debugging might be useful > especially when the owner is not really obvious from the page state. > I also agree that if the output is swapping the logs then the situation > is not really great either. Would something like the below work for your > situation? > > MAGIC_NUMBER would need to be somehow figured but I would start with 10 > or so. > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index b44d4c7ba73b..3da5c434fb77 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1299,6 +1299,8 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > LIST_HEAD(source); > > for (pfn = start_pfn; pfn < end_pfn; pfn++) { > + int dumped_page = MAGIC_NUMBER; > + > if (!pfn_valid(pfn)) > continue; > page = pfn_to_page(pfn); > @@ -1344,7 +1346,10 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > > } else { > pr_warn("failed to isolate pfn %lx\n", pfn); > - dump_page(page, "isolation failed"); > + if (dumped_page--) { > + dump_page(page, "isolation failed"); > + dumped_page = true; > + } > } > put_page(page); > } > @@ -1372,10 +1377,14 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > ret = migrate_pages(&source, alloc_migration_target, NULL, > (unsigned long)&mtc, MIGRATE_SYNC, MR_MEMORY_HOTPLUG); > if (ret) { > + int dumped_page = MAGIC_NUMBER; > + > list_for_each_entry(page, &source, lru) { > pr_warn("migrating pfn %lx failed ret:%d ", > page_to_pfn(page), ret); > - dump_page(page, "migration failure"); > + if (dumped_page--) { > + dump_page(page, "migration failure"); > + } > } > putback_movable_pages(&source); > } > These are working. Rate limiting these logs with default rate limit interval and burst also helping me. Thanks!! -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project