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 CB8B1C433EF for ; Wed, 1 Jun 2022 02:11:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349118AbiFACLW (ORCPT ); Tue, 31 May 2022 22:11:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39812 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231168AbiFACLU (ORCPT ); Tue, 31 May 2022 22:11:20 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6AF2090CE8 for ; Tue, 31 May 2022 19:11:19 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.53]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4LCXfR73jyzjWvV; Wed, 1 Jun 2022 10:10:07 +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; Wed, 1 Jun 2022 10:11:17 +0800 Subject: Re: [PATCH 2/3] mm/swapfile: avoid confusing swap cache statistics To: David Hildenbrand , Andrew Morton CC: , References: <20220527092626.31883-1-linmiaohe@huawei.com> <20220527092626.31883-3-linmiaohe@huawei.com> <20220530160409.c9b17085adb6112d8580f37d@linux-foundation.org> <33d6aec8-b4fc-aa37-27f4-f33984ea33d3@redhat.com> From: Miaohe Lin Message-ID: Date: Wed, 1 Jun 2022 10:11:16 +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: <33d6aec8-b4fc-aa37-27f4-f33984ea33d3@redhat.com> 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 20:58, David Hildenbrand wrote: > On 31.05.22 04:55, Miaohe Lin wrote: >> 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? > > I'm wondering who cares and why? I thought it's used to show the effectiveness of the swapcache readahead algorithm. If nobody ever cares about it now, I'm fine to drop this patch. And could these statistics be removed since nobody cares about it? Thanks! > >