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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 D019FC07E99 for ; Mon, 12 Jul 2021 11:03:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B4C2A60FF4 for ; Mon, 12 Jul 2021 11:03:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235434AbhGLLGe (ORCPT ); Mon, 12 Jul 2021 07:06:34 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:10471 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235410AbhGLLGa (ORCPT ); Mon, 12 Jul 2021 07:06:30 -0400 Received: from dggeme703-chm.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4GNglr0hmxzccSn; Mon, 12 Jul 2021 19:00:24 +0800 (CST) Received: from [10.174.178.125] (10.174.178.125) by dggeme703-chm.china.huawei.com (10.1.199.99) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Mon, 12 Jul 2021 19:03:39 +0800 Subject: Re: [PATCH 1/5] mm/vmscan: put the redirtied MADV_FREE pages back to anonymous LRU list To: Michal Hocko CC: , , , , , , , , , , , , , References: <20210710100329.49174-1-linmiaohe@huawei.com> <20210710100329.49174-2-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: <9409189e-44f7-2608-68af-851629b6d453@huawei.com> Date: Mon, 12 Jul 2021 19:03:39 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.125] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggeme703-chm.china.huawei.com (10.1.199.99) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/7/12 15:22, Michal Hocko wrote: > On Sat 10-07-21 18:03:25, Miaohe Lin wrote: >> If the MADV_FREE pages are redirtied before they could be reclaimed, put >> the pages back to anonymous LRU list by setting SwapBacked flag and the >> pages will be reclaimed in normal swapout way. Otherwise MADV_FREE pages >> won't be reclaimed as expected. > > Could you describe problem which you are trying to address? What does it > mean that pages won't be reclaimed as expected? > In fact, this is not a bug and harmless. But it looks buggy as it didn't perform the expected ops from code view. Lazyfree (MADV_FREE) pages are clean anonymous pages. They have SwapBacked flag cleared to distinguish normal anonymous pages. When the MADV_FREE pages are redirtied before they could be reclaimed, the pages should be put back to anonymous LRU list by setting SwapBacked flag, thus the pages will be reclaimed in normal swapout way. Many thanks for review and reply. > Also why is SetPageSwapBacked in shrink_page_list insufficient? > >> Fixes: 802a3a92ad7a ("mm: reclaim MADV_FREE pages") >> Signed-off-by: Miaohe Lin >> --- >> mm/vmscan.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index a7602f71ec04..6483fe0e2065 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -1628,6 +1628,7 @@ static unsigned int shrink_page_list(struct list_head *page_list, >> if (!page_ref_freeze(page, 1)) >> goto keep_locked; >> if (PageDirty(page)) { >> + SetPageSwapBacked(page); >> page_ref_unfreeze(page, 1); >> goto keep_locked; >> } >> -- >> 2.23.0 >