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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 01980C433EF for ; Sat, 25 Jun 2022 03:18:16 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 888398E028A; Fri, 24 Jun 2022 23:18:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 80FFF8E0287; Fri, 24 Jun 2022 23:18:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6B0D88E028A; Fri, 24 Jun 2022 23:18:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 566648E0287 for ; Fri, 24 Jun 2022 23:18:16 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 326CD606BF for ; Sat, 25 Jun 2022 03:18:16 +0000 (UTC) X-FDA: 79615299792.02.AD14A8E Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by imf19.hostedemail.com (Postfix) with ESMTP id 4F0171A0021 for ; Sat, 25 Jun 2022 03:18:15 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4LVJzM6dL8z1KCD2; Sat, 25 Jun 2022 11:15:59 +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; Sat, 25 Jun 2022 11:18:10 +0800 Subject: Re: [PATCH 14/16] mm/huge_memory: fix comment of page_deferred_list To: Zach O'Keefe CC: Muchun Song , , , , , References: <20220622170627.19786-1-linmiaohe@huawei.com> <20220622170627.19786-15-linmiaohe@huawei.com> <0b1a1633-2e07-87df-b707-3058353f5609@huawei.com> From: Miaohe Lin Message-ID: <22e8cac7-2d3d-6099-9875-70e2ea007343@huawei.com> Date: Sat, 25 Jun 2022 11:18:09 +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: dggems701-chm.china.huawei.com (10.3.19.178) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656127095; a=rsa-sha256; cv=none; b=icDjowXamBPf2xc0ci4iw17J+D3UDfDJjX++U01pkEx0d4QN9yBuC9Veh31HousDM4vEVO iXxIqtmY+XFE3R2IoJ+SQRhWoyDM8U0fV31gyfi70qkDeCbZ0MC3tXXVe83Zlzz6shdkGA gHQ8MEUT9CWGlEABYRFga+Zfq5/GmRk= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656127095; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=k9knU5oSRTDM69SxrWkAK+NM4mCxzVv4YM0OEUAYP3A=; b=Dy2yCYoaNcrf9O3V9a2q+hYjjLzGWZfSIC8RU68VNLzAH2YW0r7ZDlF6JxbOylRt/gLxeU 7JERLJBrpTFNO1Z3eqMvnWh8XDswr6MnrfW6CIKoTYxiCzbaF3j+5bx8FymKHx+BPeLNSE wIs5odR2KbGNvYDk2zQDgqbTK0wFV6w= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf19.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Stat-Signature: pjnn887onz8cu7khh5dz7onomir9gn1e X-Rspamd-Queue-Id: 4F0171A0021 Authentication-Results: imf19.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf19.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1656127095-296584 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2022/6/25 1:09, Zach O'Keefe wrote: > On 23 Jun 20:26, Miaohe Lin wrote: >> On 2022/6/23 15:24, Muchun Song wrote: >>> On Thu, Jun 23, 2022 at 01:06:25AM +0800, Miaohe Lin wrote: >>>> The current comment is confusing because if global or memcg deferred list >>>> in the second tail page is occupied by compound_head, why we still use >>>> page[2].deferred_list here? I think it wants to say that Global or memcg >>>> deferred list in the first tail page is occupied by compound_mapcount and >>>> compound_pincount so we use the second tail page's deferred_list instead. >>>> >>>> Signed-off-by: Miaohe Lin >>>> --- >>>> include/linux/huge_mm.h | 4 ++-- >>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >>>> index 12b297f9951d..2e8062b3417a 100644 >>>> --- a/include/linux/huge_mm.h >>>> +++ b/include/linux/huge_mm.h >>>> @@ -294,8 +294,8 @@ static inline bool thp_migration_supported(void) >>>> static inline struct list_head *page_deferred_list(struct page *page) >>>> { >>>> /* >>>> - * Global or memcg deferred list in the second tail pages is >>>> - * occupied by compound_head. >>>> + * Global or memcg deferred list in the first tail page is >>>> + * occupied by compound_mapcount and compound_pincount. >>>> */ >>> >>> The structure of "struct page" seems to have told us the information that >>> we resue the 2nd tail page to be used as deferred_list. I am not sure the >> >> Yes, it does. >> >>> value of those comments. Maybe better to remove them? >> >> IMHO above comment tries to tell us why deferred list in the second tail page is used >> instead of first tail page. But it should be fine to remove the above comments as they >> don't seem to provide much info (thought I'm not really sure). >> >> Thanks. >> > > Just a suggestion - feel free to disregard. Maybe we don't need to repeat the > comments in struct page, but maybe a "see organization of tail pages of compound > page in "struct page" definition" would at least point new people to where this > magic 2 comes from. Maybe an obvious place to check after you're familiar with > overloading struct page data for compound pages - but IMO it's not obvious for > newcomers. This is a good suggestion to me. Thanks! > >>> >>> Thanks. >>> >>>> return &page[2].deferred_list; >>>> } >>>> -- >>>> 2.23.0 >>>> >>>> >>> . >>> >> > . >