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 D40DDC433EF for ; Thu, 31 Mar 2022 07:44:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232371AbiCaHqD (ORCPT ); Thu, 31 Mar 2022 03:46:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53696 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232336AbiCaHpz (ORCPT ); Thu, 31 Mar 2022 03:45:55 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 88744D7636 for ; Thu, 31 Mar 2022 00:44:06 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4KTb0208TjzdZQw; Thu, 31 Mar 2022 15:43:46 +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 15.1.2308.21; Thu, 31 Mar 2022 15:44:04 +0800 Subject: Re: [PATCH 1/8] mm/vmscan: remove redundant folio_test_swapbacked check when folio is file lru To: "Huang, Ying" CC: Andrew Morton , Linux Memory Management List , LKML , Muchun Song References: <20220329132619.18689-1-linmiaohe@huawei.com> <20220329132619.18689-2-linmiaohe@huawei.com> <87lewqbpad.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Miaohe Lin Message-ID: <7c8d06f6-ac41-d3d7-f6b6-20a06e56dc61@huawei.com> Date: Thu, 31 Mar 2022 15:44:03 +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: <87lewqbpad.fsf@yhuang6-desk2.ccr.corp.intel.com> Content-Type: text/plain; charset="windows-1252" 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 2022/3/31 14:37, Huang, Ying wrote: > Muchun Song writes: > >> On Tue, Mar 29, 2022 at 9:26 PM Miaohe Lin wrote: >>> >>> When folio is file lru, folio_test_swapbacked is guaranteed to be true. So >>> it's unnecessary to check it here again. No functional change intended. >>> >>> Signed-off-by: Miaohe Lin >>> --- >>> mm/vmscan.c | 3 +-- >>> 1 file changed, 1 insertion(+), 2 deletions(-) >>> >>> diff --git a/mm/vmscan.c b/mm/vmscan.c >>> index 1678802e03e7..7c1a9713bfc9 100644 >>> --- a/mm/vmscan.c >>> +++ b/mm/vmscan.c >>> @@ -1434,8 +1434,7 @@ static void folio_check_dirty_writeback(struct folio *folio, >>> * Anonymous pages are not handled by flushers and must be written >>> * from reclaim context. Do not stall reclaim based on them >>> */ >>> - if (!folio_is_file_lru(folio) || >>> - (folio_test_anon(folio) && !folio_test_swapbacked(folio))) { >>> + if (!folio_is_file_lru(folio) || folio_test_anon(folio)) { >> >> At least your login is no problem since folio_is_file_lru() is equal to >> !folio_test_swapbacked(). But the new code is not clear to me. >> The old code is easy to understand, e.g. folio_test_anon(folio) && >> !folio_test_swapbacked(folio) tells us that the anon pages which >> do not need to be swapped should be skipped. > > That is for MADV_FREE pages. The code is introduced in commit > 802a3a92ad7a ("mm: reclaim MADV_FREE pages"). > > So I think the original code is better. It's an implementation detail > that folio_is_file_lru() equals !folio_test_swapbacked(). It may be > better to add some comments here for MADV_FREE pages. > Do you tend to drop this patch or adding a comment with the change in this patch or something else? Thanks. >> So I'm neutral on the patch. > > Best Regards, > Huang, Ying > . >