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=-8.3 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 46ACBC433E0 for ; Tue, 11 Aug 2020 13:01:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1627B2076B for ; Tue, 11 Aug 2020 13:01:32 +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="MYBrA2do" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728668AbgHKNBb (ORCPT ); Tue, 11 Aug 2020 09:01:31 -0400 Received: from m43-7.mailgun.net ([69.72.43.7]:46387 "EHLO m43-7.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728506AbgHKNB3 (ORCPT ); Tue, 11 Aug 2020 09:01:29 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1597150889; h=Content-Transfer-Encoding: Content-Type: In-Reply-To: MIME-Version: Date: Message-ID: From: References: Cc: To: Subject: Sender; bh=HNVJh0REjWkPwPjY9yj6feAv3ggEjHvlkWIzWMdpnXo=; b=MYBrA2doxcP9lACb3FZ6pcn9bjEqYuY9je3cRbgkf87HHNKNfoIU3k40qOwCZxRoEOs2J6NO /hsujmS4PXXrK8cS4YJdgRvu9Z3UvPJWk321AafLOWLumJTiLtCLyDvINsepW+o4O+ttwKLz oCAXETxnlZWg/m9JplsG5kcxmNg= X-Mailgun-Sending-Ip: 69.72.43.7 X-Mailgun-Sid: WyI0MWYwYSIsICJsaW51eC1rZXJuZWxAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n04.prod.us-east-1.postgun.com with SMTP id 5f329697440a07969ae21ee9 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Tue, 11 Aug 2020 13:01:11 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 1CACDC433CA; Tue, 11 Aug 2020 13:01:11 +0000 (UTC) Received: from [192.168.1.103] (unknown [183.83.143.239]) (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 D5E5BC433C6; Tue, 11 Aug 2020 13:01:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org D5E5BC433C6 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=none smtp.mailfrom=charante@codeaurora.org Subject: Re: [PATCH] mm, page_alloc: fix core hung in free_pcppages_bulk() To: David Rientjes Cc: akpm@linux-foundation.org, mhocko@suse.com, vbabka@suse.cz, david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, vinmenon@codeaurora.org References: <1597075833-16736-1-git-send-email-charante@codeaurora.org> From: Charan Teja Kalla Message-ID: Date: Tue, 11 Aug 2020 18:31:05 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 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 Thanks David. On 8/11/2020 1:06 AM, David Rientjes wrote: > On Mon, 10 Aug 2020, Charan Teja Reddy wrote: > >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index e4896e6..25e7e12 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -3106,6 +3106,7 @@ static void free_unref_page_commit(struct page *page, unsigned long pfn) >> struct zone *zone = page_zone(page); >> struct per_cpu_pages *pcp; >> int migratetype; >> + int high; >> >> migratetype = get_pcppage_migratetype(page); >> __count_vm_event(PGFREE); >> @@ -3128,8 +3129,19 @@ static void free_unref_page_commit(struct page *page, unsigned long pfn) >> pcp = &this_cpu_ptr(zone->pageset)->pcp; >> list_add(&page->lru, &pcp->lists[migratetype]); >> pcp->count++; >> - if (pcp->count >= pcp->high) { >> - unsigned long batch = READ_ONCE(pcp->batch); >> + high = READ_ONCE(pcp->high); >> + if (pcp->count >= high) { >> + int batch; >> + >> + batch = READ_ONCE(pcp->batch); >> + /* >> + * For non-default pcp struct values, high is always >> + * greater than the batch. If high < batch then pass >> + * proper count to free the pcp's list pages. >> + */ >> + if (unlikely(high < batch)) >> + batch = min(pcp->count, batch); >> + >> free_pcppages_bulk(zone, batch, pcp); >> } >> } > > I'm wondering if a fix to free_pcppages_bulk() is more appropriate here > because the count passed into it seems otherwise fragile if this results > in a hung core? > Agree that the free_pcppages_bulk() is appropriate place to fix and it actually much cleaner. Raised V2: https://patchwork.kernel.org/patch/11709225/ -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project