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 C30ECECAAD4 for ; Sat, 27 Aug 2022 02:48:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E70516B0073; Fri, 26 Aug 2022 22:48:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DF8566B0074; Fri, 26 Aug 2022 22:48:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C7205940007; Fri, 26 Aug 2022 22:48:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id B3BE66B0073 for ; Fri, 26 Aug 2022 22:48:40 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 8962D1408D0 for ; Sat, 27 Aug 2022 02:48:40 +0000 (UTC) X-FDA: 79843839600.14.F4C2565 Received: from out1.migadu.com (out1.migadu.com [91.121.223.63]) by imf20.hostedemail.com (Postfix) with ESMTP id DD8F41C0029 for ; Sat, 27 Aug 2022 02:48:39 +0000 (UTC) Content-Type: text/plain; charset=utf-8 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1661568518; h=from:from: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=pDNO5snsfzZ0QfiFLp+wtvtFYkVtacMwaYUOIIg95Vk=; b=k8ARJIaZnV00D1GHc+/8GObxNNbysxo1gwRwuiDJyVku0ekFoxwVX0fP3AOTbAZ+IbVFP7 nOq8hBEKMMTTeANzIY7o9onqZKRHNLvvWBaKQubh009bQ4jnSo6lpeW8eS3tBmQwLwNIJ0 UxDD6bCMc1n1/Y97tW4zXEnxzrufFmc= MIME-Version: 1.0 Subject: Re: [PATCH 03/10] hugetlb: Use LIST_HEAD() to define a list head X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Muchun Song In-Reply-To: Date: Sat, 27 Aug 2022 10:48:34 +0800 Cc: Andrew Morton , mike.kravetz@oracle.com, Muchun Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <83DBE074-0B63-4CB2-9BD2-65967977B69C@linux.dev> References: <20220826092422.39591-1-linmiaohe@huawei.com> <20220826092422.39591-4-linmiaohe@huawei.com> <8D011A6F-F557-4519-852C-80BBDE53E630@linux.dev> To: Miaohe Lin X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=k8ARJIaZ; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf20.hostedemail.com: domain of muchun.song@linux.dev designates 91.121.223.63 as permitted sender) smtp.mailfrom=muchun.song@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661568520; a=rsa-sha256; cv=none; b=NXjE2gKFzQe/tivmkhF5sjzHaOSmw6L3OH+BQzhXXgBlACqhSsgl+N2c6VpnCV/BCXzYGz 0vmiZg2ToJ/yeQ7UHpQccEkdHgqAbGpduotp4JmniLj8uWrtOIUP3ZF/QcpJj5wT0Qs9B2 FH/9cSgN6rvZfEeoPrkS/UmZk2qOETY= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661568520; 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:dkim-signature; bh=pDNO5snsfzZ0QfiFLp+wtvtFYkVtacMwaYUOIIg95Vk=; b=N3EhAmQvK/F9860xaVbLma3HQxLq0SQNhzPo4CTU35TcFf05f9BX0d3Ag4wXSGVk0TIcm9 n777F7FpEiC4UIJ8k7gt1+BN3fl/Yn4xsMYRroO79SaEiJ3J90s8JMvNnQtHnLTL/4E0Jm kjDpHOsl5fzteZ8hDLkgOQIMpfEzWu4= X-Rspam-User: X-Rspamd-Queue-Id: DD8F41C0029 Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=k8ARJIaZ; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf20.hostedemail.com: domain of muchun.song@linux.dev designates 91.121.223.63 as permitted sender) smtp.mailfrom=muchun.song@linux.dev X-Stat-Signature: udmptgryn7oyfzi9qm9a4gzsh435d7sg X-Rspamd-Server: rspam03 X-HE-Tag: 1661568519-45555 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 Aug 27, 2022, at 10:27, Miaohe Lin wrote: >=20 > On 2022/8/27 9:47, Muchun Song wrote: >>=20 >>=20 >>> On Aug 26, 2022, at 17:24, Miaohe Lin wrote: >>>=20 >>> We can avoid unneeded WRITE_ONCE() overhead by using LIST_HEAD() to = define >>> a list head. >>=20 >> IIUC, the overhead doesn=E2=80=99t change. Right? >=20 > I think the overhead is changed. LIST_HEAD is initialized without = using WRITE_ONCE(): I think there is no special difference with "WRITE_ONCE(var, 0)" vs "var = =3D 0=E2=80=9D in assembly code. Both code of line will be compiled to a mov or movq = instruction. I didn=E2=80=99t confirm if the assembly code is different (I tend to = think it is similar). Just some analysis from me. >=20 > #define LIST_HEAD_INIT(name) { &(name), &(name) } >=20 > #define LIST_HEAD(name) \ > struct list_head name =3D LIST_HEAD_INIT(name) >=20 > while INIT_LIST_HEAD has: >=20 > static inline void INIT_LIST_HEAD(struct list_head *list) > { > WRITE_ONCE(list->next, list); > WRITE_ONCE(list->prev, list); > } >=20 > Or am I miss something? >=20 >>=20 >> I=E2=80=99m fine with your changes. >>=20 >> Reviewed-by: Muchun Song >=20 > Many thanks for your review and comment. :) >=20 > Thanks, > Miaohe Lin >=20