From patchwork Tue Apr 6 19:30:32 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 12185771 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=-18.8 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,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 32D71C433ED for ; Tue, 6 Apr 2021 19:30:52 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D2207613A9 for ; Tue, 6 Apr 2021 19:30:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D2207613A9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.106274.203273 (Exim 4.92) (envelope-from ) id 1lTrPK-0005BU-Sg; Tue, 06 Apr 2021 19:30:38 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 106274.203273; Tue, 06 Apr 2021 19:30:38 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lTrPK-0005BN-PO; Tue, 06 Apr 2021 19:30:38 +0000 Received: by outflank-mailman (input) for mailman id 106274; Tue, 06 Apr 2021 19:30:37 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lTrPJ-0005BI-Fv for xen-devel@lists.xenproject.org; Tue, 06 Apr 2021 19:30:37 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lTrPI-0005lS-2f; Tue, 06 Apr 2021 19:30:36 +0000 Received: from 54-240-197-235.amazon.com ([54.240.197.235] helo=ufe34d9ed68d054.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lTrPH-0001Rg-KB; Tue, 06 Apr 2021 19:30:35 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Message-Id:Date:Subject:Cc:To:From; bh=x4BrDhgOv8YmGzD+ftCZACZopXD6GRxTjZmC0jrBQLM=; b=n0wktH0f3NmU0il91SKdTEdpYt BYo9yeAFLqHa5Cvz4DGgqHO82fOrAYvRvI8WlfPl1jWTY4MbyqezmgohHRdCVNIxl7x/dMy25qOJN lESxgOhYCKRF/EOvWuyk6hDEBqCq7bQhQqLCBQ1DskrPl0/kJKSEPDlRHthhLZp5Dbew=; From: Julien Grall To: xen-devel@lists.xenproject.org Cc: julien@xen.org, Julien Grall , Andrew Cooper , George Dunlap , Ian Jackson , Jan Beulich , Stefano Stabellini , Wei Liu Subject: [PATCH] xen/page_alloc: Don't hold the heap_lock when clearing PGC_need_scrub Date: Tue, 6 Apr 2021 20:30:32 +0100 Message-Id: <20210406193032.16976-1-julien@xen.org> X-Mailer: git-send-email 2.17.1 From: Julien Grall Currently, the heap_lock is held when clearing PGC_need_scrub in alloc_heap_pages(). However, this is unnecessary because the only caller (mark_page_offline()) that can concurrently modify the count_info is using cmpxchg() in a loop. Therefore, rework the code to avoid holding the heap_lock and use test_and_clear_bit() instead. Signed-off-by: Julien Grall Reviewed-by: Jan Beulich --- xen/common/page_alloc.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c index 68e47d963842..70146a00ec8b 100644 --- a/xen/common/page_alloc.c +++ b/xen/common/page_alloc.c @@ -1038,16 +1038,12 @@ static struct page_info *alloc_heap_pages( { for ( i = 0; i < (1U << order); i++ ) { - if ( test_bit(_PGC_need_scrub, &pg[i].count_info) ) + if ( test_and_clear_bit(_PGC_need_scrub, &pg[i].count_info) ) { if ( !(memflags & MEMF_no_scrub) ) scrub_one_page(&pg[i]); dirty_cnt++; - - spin_lock(&heap_lock); - pg[i].count_info &= ~PGC_need_scrub; - spin_unlock(&heap_lock); } else if ( !(memflags & MEMF_no_scrub) ) check_one_page(&pg[i]);