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 X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 3FD3AC43461 for ; Wed, 5 May 2021 01:34:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1F01861404 for ; Wed, 5 May 2021 01:34:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231980AbhEEBfK (ORCPT ); Tue, 4 May 2021 21:35:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:38052 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231124AbhEEBfI (ORCPT ); Tue, 4 May 2021 21:35:08 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7933B613FE; Wed, 5 May 2021 01:34:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1620178452; bh=sdfnsO70M8Ltp1wioWUxSgGD1EdnyX/pvWylNy0Z6To=; h=Date:From:To:Subject:In-Reply-To:From; b=jtiitdgrdc9MWBTE9fIaTsPUWRtkazR/PXWSAhb/wb3SrA4aPrRd8uNWYaBxC4Y46 m9lSuYg1GZ94MLhChmWxVDtnVMzLsXP2Xwd8xx7q9I3RhYI+WCdhw8915vYf29sTYf rKdZTtP1TS7ESPY0roRIrftmTWgcOGhlX7NDgWfs= Date: Tue, 04 May 2021 18:34:12 -0700 From: Andrew Morton To: akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, linux-mm@kvack.org, mike.kravetz@oracle.com, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, yanfei.xu@windriver.com Subject: [patch 028/143] mm/khugepaged.c: replace barrier() with READ_ONCE() for a selective variable Message-ID: <20210505013412.wFqTFyLJJ%akpm@linux-foundation.org> In-Reply-To: <20210504183219.a3cc46aee4013d77402276c5@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Yanfei Xu Subject: mm/khugepaged.c: replace barrier() with READ_ONCE() for a selective variable READ_ONCE() is more selective and lightweight. It is more appropriate that using a READ_ONCE() for the certain variable to prevent the compiler from reordering. Link: https://lkml.kernel.org/r/20210323092730.247583-1-yanfei.xu@windriver.com Signed-off-by: Yanfei Xu Acked-by: Kirill A. Shutemov Cc: Mike Kravetz Signed-off-by: Andrew Morton --- mm/khugepaged.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/mm/khugepaged.c~khugepaged-raplace-barrier-with-read_once-for-a-selective-variable +++ a/mm/khugepaged.c @@ -2202,11 +2202,9 @@ static void khugepaged_do_scan(void) { struct page *hpage = NULL; unsigned int progress = 0, pass_through_head = 0; - unsigned int pages = khugepaged_pages_to_scan; + unsigned int pages = READ_ONCE(khugepaged_pages_to_scan); bool wait = true; - barrier(); /* write khugepaged_pages_to_scan to local stack */ - lru_add_drain_all(); while (progress < pages) { _