From patchwork Thu Mar 18 12:27:18 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miaohe Lin X-Patchwork-Id: 12148073 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,URIBL_BLOCKED,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 66165C433E0 for ; Thu, 18 Mar 2021 12:28:11 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BB1CB64F41 for ; Thu, 18 Mar 2021 12:28:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BB1CB64F41 Authentication-Results: mail.kernel.org; dmarc=fail (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 49E766B0078; Thu, 18 Mar 2021 08:28:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 435116B0075; Thu, 18 Mar 2021 08:28:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 314C76B0075; Thu, 18 Mar 2021 08:28:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0167.hostedemail.com [216.40.44.167]) by kanga.kvack.org (Postfix) with ESMTP id 165066B0073 for ; Thu, 18 Mar 2021 08:28:10 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id DD003824999B for ; Thu, 18 Mar 2021 12:28:09 +0000 (UTC) X-FDA: 77932922298.07.6F9B80F Received: from szxga05-in.huawei.com (szxga05-in.huawei.com [45.249.212.191]) by imf17.hostedemail.com (Postfix) with ESMTP id 101F6407F8EB for ; Thu, 18 Mar 2021 12:28:08 +0000 (UTC) Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4F1R8M4YtkzrYQl; Thu, 18 Mar 2021 20:26:11 +0800 (CST) Received: from huawei.com (10.175.104.175) by DGGEMS406-HUB.china.huawei.com (10.3.19.206) with Microsoft SMTP Server id 14.3.498.0; Thu, 18 Mar 2021 20:27:56 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , , Subject: [PATCH v3 2/6] mm/huge_memory.c: make get_huge_zero_page() return bool Date: Thu, 18 Mar 2021 08:27:18 -0400 Message-ID: <20210318122722.13135-3-linmiaohe@huawei.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20210318122722.13135-1-linmiaohe@huawei.com> References: <20210318122722.13135-1-linmiaohe@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.104.175] X-CFilter-Loop: Reflected X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 101F6407F8EB X-Stat-Signature: j8b7ap3iguj1hkc5toohpbik6wm5wiae Received-SPF: none (huawei.com>: No applicable sender policy available) receiver=imf17; identity=mailfrom; envelope-from=""; helo=szxga05-in.huawei.com; client-ip=45.249.212.191 X-HE-DKIM-Result: none/none X-HE-Tag: 1616070488-315131 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 ae16a82da823..01b96c638e73 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)