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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7DF3FC433F5 for ; Tue, 31 May 2022 02:55:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243671AbiEaCz0 (ORCPT ); Mon, 30 May 2022 22:55:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58830 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232746AbiEaCzX (ORCPT ); Mon, 30 May 2022 22:55:23 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E3D798CCFB for ; Mon, 30 May 2022 19:55:22 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4LBxdW6NSLzQkNx; Tue, 31 May 2022 10:52:15 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 31 May 2022 10:55:20 +0800 Subject: Re: [PATCH 2/3] mm/swapfile: avoid confusing swap cache statistics To: Andrew Morton CC: , References: <20220527092626.31883-1-linmiaohe@huawei.com> <20220527092626.31883-3-linmiaohe@huawei.com> <20220530160409.c9b17085adb6112d8580f37d@linux-foundation.org> From: Miaohe Lin Message-ID: Date: Tue, 31 May 2022 10:55:20 +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: <20220530160409.c9b17085adb6112d8580f37d@linux-foundation.org> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/5/31 7:04, Andrew Morton wrote: > On Fri, 27 May 2022 17:26:25 +0800 Miaohe Lin wrote: > >> At swapoff time, we're going to swap in the pages continuously. So calling >> lookup_swap_cache would confuse statistics. We should use find_get_page >> directly here. > > Why is the existing behaviour wrong? swapoff() has to swap stuff in to > be able to release the swap device. Why do you believe that this > swapin activity should not be accounted? IMHO, statistics, e.g. swap_cache_info.find_success, are used to show the effectiveness of the swap cache activity. So they should only reflect the memory accessing activity of the user. I think swapoff can't reflect the effectiveness of the swap cache activity because it just swaps in pages one by one. Or statistics should reflect all the activity of the user including swapoff? Thanks! > > > . >