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=-4.0 required=3.0 tests=MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS 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 56C63C43387 for ; Thu, 20 Dec 2018 05:54:55 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C4C1020815 for ; Thu, 20 Dec 2018 05:54:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C4C1020815 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 43L1Dr6JbqzDqgf for ; Thu, 20 Dec 2018 16:54:52 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=linux.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=aneesh.kumar@linux.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 43L1BQ5CdczDqw1 for ; Thu, 20 Dec 2018 16:52:46 +1100 (AEDT) Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id wBK5oaAT122822 for ; Thu, 20 Dec 2018 00:52:44 -0500 Received: from e11.ny.us.ibm.com (e11.ny.us.ibm.com [129.33.205.201]) by mx0a-001b2d01.pphosted.com with ESMTP id 2pg59pr2y6-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 20 Dec 2018 00:52:44 -0500 Received: from localhost by e11.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 20 Dec 2018 05:52:38 -0000 Received: from b01ledav006.gho.pok.ibm.com (b01ledav006.gho.pok.ibm.com [9.57.199.111]) by b01cxnp23034.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id wBK5qbMD17629256 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 20 Dec 2018 05:52:37 GMT Received: from b01ledav006.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 75C84AC062; Thu, 20 Dec 2018 05:52:37 +0000 (GMT) Received: from b01ledav006.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 61112AC059; Thu, 20 Dec 2018 05:52:34 +0000 (GMT) Received: from [9.85.68.89] (unknown [9.85.68.89]) by b01ledav006.gho.pok.ibm.com (Postfix) with ESMTP; Thu, 20 Dec 2018 05:52:33 +0000 (GMT) Subject: Re: [PATCH V5 1/3] mm: Add get_user_pages_cma_migrate To: Alexey Kardashevskiy , akpm@linux-foundation.org, Michal Hocko , mpe@ellerman.id.au, paulus@samba.org, David Gibson References: <20181219034047.16305-1-aneesh.kumar@linux.ibm.com> <20181219034047.16305-2-aneesh.kumar@linux.ibm.com> <23cae5a6-4370-224c-523c-ab6ee940cf87@ozlabs.ru> From: "Aneesh Kumar K.V" Date: Thu, 20 Dec 2018 11:22:32 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.1 MIME-Version: 1.0 In-Reply-To: <23cae5a6-4370-224c-523c-ab6ee940cf87@ozlabs.ru> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 18122005-2213-0000-0000-0000032E668E X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010253; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000271; SDB=6.01134327; UDB=6.00589763; IPR=6.00914499; MB=3.00024763; MTD=3.00000008; XFM=3.00000015; UTC=2018-12-20 05:52:41 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18122005-2214-0000-0000-00005CAC0B05 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2018-12-20_03:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=18 phishscore=0 bulkscore=0 spamscore=0 clxscore=-1004 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1812200048 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 12/20/18 11:18 AM, Alexey Kardashevskiy wrote: > > > On 20/12/2018 16:22, Aneesh Kumar K.V wrote: >> On 12/20/18 9:49 AM, Alexey Kardashevskiy wrote: >>> >>> >>> On 19/12/2018 14:40, Aneesh Kumar K.V wrote: >>>> This helper does a get_user_pages_fast and if it find pages in the >>>> CMA area >>>> it will try to migrate them before taking page reference. This makes >>>> sure that >>>> we don't keep non-movable pages (due to page reference count) in the >>>> CMA area. >>>> Not able to move pages out of CMA area result in CMA allocation >>>> failures. >>>> >>>> Signed-off-by: Aneesh Kumar K.V >>> >> >> ..... >>>> +         * We did migrate all the pages, Try to get the page >>>> references again >>>> +         * migrating any new CMA pages which we failed to isolate >>>> earlier. >>>> +         */ >>>> +        drain_allow = true; >>>> +        goto get_user_again; >>> >>> >>> So it is possible to have pages pinned, then successfully migrated >>> (migrate_pages() returned 0), then pinned again, then some pages may end >>> up in CMA again and migrate again and nothing seems to prevent this loop >>> from being endless. What do I miss? >>> >> >> pages used as target page for migration won't be allocated from CMA region. > > > Then migrate_allow should be set to "false" regardless what > migrate_pages() returned and then I am totally missing the point of this > goto and going through the loop again even when we know for sure it > won't do literally anything but checking is_migrate_cma_page() even > though we know pages won't be allocated from CMA. > Because we might have failed to isolate all the pages in the first attempt. -aneesh