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 7BB6BC433EF for ; Tue, 12 Apr 2022 13:42:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352939AbiDLNok (ORCPT ); Tue, 12 Apr 2022 09:44:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57146 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236249AbiDLNoh (ORCPT ); Tue, 12 Apr 2022 09:44:37 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BE3884ECCE for ; Tue, 12 Apr 2022 06:42:18 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Kd6MV07y1zdZcX; Tue, 12 Apr 2022 21:41:42 +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, 12 Apr 2022 21:42:16 +0800 Subject: Re: [PATCH v2 2/9] mm/vmscan: remove unneeded can_split_huge_page check To: Oscar Salvador CC: , , , , , , References: <20220409093500.10329-1-linmiaohe@huawei.com> <20220409093500.10329-3-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: <7455b680-3d89-5d3e-ba0e-6e4358b114a2@huawei.com> Date: Tue, 12 Apr 2022 21:42:16 +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: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) 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 2022/4/12 16:59, Oscar Salvador wrote: > On Sat, Apr 09, 2022 at 05:34:53PM +0800, Miaohe Lin wrote: >> We don't need to check can_split_folio() because folio_maybe_dma_pinned() >> is checked before. It will avoid the long term pinned pages to be swapped >> out. And we can live with short term pinned pages. Without can_split_folio >> checking we can simplify the code. Also activate_locked can be changed to >> keep_locked as it's just short term pinning. > > What do you mean by "we can live with short term pinned pages"? > Does it mean that it was not pinned when we check > folio_maybe_dma_pinned() but now it is? > > To me it looks like the pinning is fluctuating and we rely on > split_folio_to_list() to see whether we succeed or not, and if not > we give it another spin in the next round? Yes. Short term pinned pages is relative to long term pinned pages and these pages won't be pinned for a noticeable time. So it's expected to split the folio successfully in the next round as the pinning is really fluctuating. Or am I miss something? Many thanks for your comment and reply! > >> Suggested-by: Huang, Ying >> Signed-off-by: Miaohe Lin >> --- >> mm/vmscan.c | 22 ++++++++-------------- >> 1 file changed, 8 insertions(+), 14 deletions(-) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index 4a76be47bed1..01f5db75a507 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -1711,20 +1711,14 @@ static unsigned int shrink_page_list(struct list_head *page_list, >> goto keep_locked; >> if (folio_maybe_dma_pinned(folio)) >> goto keep_locked; >> - if (PageTransHuge(page)) { >> - /* cannot split THP, skip it */ >> - if (!can_split_folio(folio, NULL)) >> - goto activate_locked; >> - /* >> - * Split pages without a PMD map right >> - * away. Chances are some or all of the >> - * tail pages can be freed without IO. >> - */ >> - if (!folio_entire_mapcount(folio) && >> - split_folio_to_list(folio, >> - page_list)) >> - goto activate_locked; >> - } >> + /* >> + * Split pages without a PMD map right >> + * away. Chances are some or all of the >> + * tail pages can be freed without IO. >> + */ >> + if (PageTransHuge(page) && !folio_entire_mapcount(folio) && >> + split_folio_to_list(folio, page_list)) >> + goto keep_locked; >> if (!add_to_swap(page)) { >> if (!PageTransHuge(page)) >> goto activate_locked_split; >> -- >> 2.23.0 >> >> >