From patchwork Sat Mar 13 10:32:21 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miaohe Lin X-Patchwork-Id: 12136789 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2DAA8C433E0 for ; Sat, 13 Mar 2021 13:52:55 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B186664F27 for ; Sat, 13 Mar 2021 13:52:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B186664F27 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 408246B0070; Sat, 13 Mar 2021 08:52:54 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 3B8A56B0071; Sat, 13 Mar 2021 08:52:54 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 282516B0072; Sat, 13 Mar 2021 08:52:54 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0096.hostedemail.com [216.40.44.96]) by kanga.kvack.org (Postfix) with ESMTP id 0C5E86B0070 for ; Sat, 13 Mar 2021 08:52:54 -0500 (EST) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id C6FA0180CCE16 for ; Sat, 13 Mar 2021 13:52:53 +0000 (UTC) X-FDA: 77914991826.23.53B65C9 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) by imf17.hostedemail.com (Postfix) with ESMTP id DCEF14A5D81E for ; Sat, 13 Mar 2021 10:33:14 +0000 (UTC) Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4DyJqZ2HrRzmWJc; Sat, 13 Mar 2021 18:30:50 +0800 (CST) Received: from huawei.com (10.175.104.175) by DGGEMS405-HUB.china.huawei.com (10.3.19.205) with Microsoft SMTP Server id 14.3.498.0; Sat, 13 Mar 2021 18:32:58 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , Subject: [PATCH 2/6] mm/huge_memory.c: make get_huge_zero_page() return bool Date: Sat, 13 Mar 2021 05:32:21 -0500 Message-ID: <20210313103225.16607-4-linmiaohe@huawei.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20210313103225.16607-1-linmiaohe@huawei.com> References: <20210313103225.16607-1-linmiaohe@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.104.175] X-CFilter-Loop: Reflected X-Stat-Signature: kcpzbcrik1em16bea9xh78zx6t4xmo8c X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: DCEF14A5D81E Received-SPF: none (huawei.com>: No applicable sender policy available) receiver=imf17; identity=mailfrom; envelope-from=""; helo=szxga04-in.huawei.com; client-ip=45.249.212.190 X-HE-DKIM-Result: none/none X-HE-Tag: 1615631594-419392 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: It's guaranteed that huge_zero_page will not be NULL if huge_zero_refcount is increased successfully. When READ_ONCE(huge_zero_page) is returned, there must be a huge_zero_page and it can be replaced with returning 'true' when we do not care about the value of huge_zero_page. We can thus make it return bool to save READ_ONCE cpu cycles as the return value is just used to check if huge_zero_page exists. Signed-off-by: Miaohe Lin --- mm/huge_memory.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 3303576489d5..6d13ca5441e2 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -77,18 +77,18 @@ bool transparent_hugepage_enabled(struct vm_area_struct *vma) return false; } -static struct page *get_huge_zero_page(void) +static bool get_huge_zero_page(void) { struct page *zero_page; retry: if (likely(atomic_inc_not_zero(&huge_zero_refcount))) - return READ_ONCE(huge_zero_page); + return true; zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, HPAGE_PMD_ORDER); if (!zero_page) { count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); - return NULL; + return false; } count_vm_event(THP_ZERO_PAGE_ALLOC); preempt_disable(); @@ -101,7 +101,7 @@ static struct page *get_huge_zero_page(void) /* We take additional reference here. It will be put back by shrinker */ atomic_set(&huge_zero_refcount, 2); preempt_enable(); - return READ_ONCE(huge_zero_page); + return true; } static void put_huge_zero_page(void)