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=-9.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 2BE77C04AB4 for ; Wed, 15 May 2019 00:31:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EE6DC20873 for ; Wed, 15 May 2019 00:31:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=synopsys.com header.i=@synopsys.com header.b="dxUetF3q" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726966AbfEOAa7 (ORCPT ); Tue, 14 May 2019 20:30:59 -0400 Received: from smtprelay-out1.synopsys.com ([198.182.61.142]:38852 "EHLO smtprelay-out1.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726841AbfEOAac (ORCPT ); Tue, 14 May 2019 20:30:32 -0400 Received: from mailhost.synopsys.com (dc8-mailhost2.synopsys.com [10.13.135.210]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by smtprelay-out1.synopsys.com (Postfix) with ESMTPS id D57C2C0A77; Wed, 15 May 2019 00:30:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=synopsys.com; s=mail; t=1557880222; bh=5nGJv3FYZ4K8QvJw3tH/+4ah4G8NKr7npBJJdtbIcCU=; h=From:To:CC:Subject:Date:In-Reply-To:References:From; b=dxUetF3qUJUHHlevAE6m9jwQCZvx5OOcNg2+jVz5i7cLUOBRhCAhkOzlgeHBt4WDS RHLDjZKA8FU3rDUPnI3vhurYt4wOt6bcBiLfDdMlSMThKlTtlpc90jQY9G3KpXeGsM LPnjSyUJn4h+LP1QkcLiIPRyqBVC87QFt/J4odXpi+Ufu8DhByVj9kpVzgCnCiP1RM QTF7fSscMqlWfHE3VOOyBqq2xtUyqSa/IRDB83We81ZdEBEg7yX+indgkT3S1+ph/W tOrT4Z9gSBRlLv8Zd0X6g75pP8t3JeGYZSRoFGZfwwCHBttf4YZD1u1kpmmg1CwNQ6 usCyvNyjo7jrQ== Received: from us01wehtc1.internal.synopsys.com (us01wehtc1-vip.internal.synopsys.com [10.12.239.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mailhost.synopsys.com (Postfix) with ESMTPS id 380E6A0068; Wed, 15 May 2019 00:30:32 +0000 (UTC) Received: from IN01WEHTCB.internal.synopsys.com (10.144.199.106) by us01wehtc1.internal.synopsys.com (10.12.239.235) with Microsoft SMTP Server (TLS) id 14.3.408.0; Tue, 14 May 2019 17:30:26 -0700 Received: from IN01WEHTCA.internal.synopsys.com (10.144.199.103) by IN01WEHTCB.internal.synopsys.com (10.144.199.105) with Microsoft SMTP Server (TLS) id 14.3.408.0; Wed, 15 May 2019 06:00:23 +0530 Received: from vineetg-Latitude-E7450.internal.synopsys.com (10.13.182.230) by IN01WEHTCA.internal.synopsys.com (10.144.199.243) with Microsoft SMTP Server (TLS) id 14.3.408.0; Wed, 15 May 2019 06:00:34 +0530 From: Vineet Gupta To: CC: , , Vineet Gupta , Peter Zijlstra Subject: [PATCH 9/9] ARC: mm: do_page_fault refactor #8: release mmap_sem sooner Date: Tue, 14 May 2019 17:29:36 -0700 Message-ID: <1557880176-24964-10-git-send-email-vgupta@synopsys.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1557880176-24964-1-git-send-email-vgupta@synopsys.com> References: <1557880176-24964-1-git-send-email-vgupta@synopsys.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.13.182.230] Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In case of successful page fault handling, this patch releases mmap_sem before updating the perf stat event for major/minor faults. So even though the contention reduction is NOT supe rhigh, it is still an improvement. There's an additional code size improvement as we only have 2 up_read() calls now. Note to myself: -------------- 1. Given the way it is done, we are forced to move @bad_area label earlier causing the various "goto bad_area" cases to hit perf stat code. - PERF_COUNT_SW_PAGE_FAULTS is NOW updated for access errors which is what arm/arm64 seem to be doing as well (with slightly different code) - PERF_COUNT_SW_PAGE_FAULTS_{MAJ,MIN} must NOT be updated for the error case which is guarded by now setting @fault initial value to VM_FAULT_ERROR which serves both cases when handle_mm_fault() returns error or is not called at all. 2. arm/arm64 use two homebrew fault flags VM_FAULT_BAD{MAP,MAPACCESS} which I was inclined to add too but seems not needed for ARC - given that we have everything is 1 function we cabn stil use goto - we setup si_code at the right place (arm* do that in the end) - we init fault already to error value which guards entry into perf stats event update Cc: Peter Zijlstra Signed-off-by: Vineet Gupta --- arch/arc/mm/fault.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c index 20402217d9da..e93ea06c214c 100644 --- a/arch/arc/mm/fault.c +++ b/arch/arc/mm/fault.c @@ -68,7 +68,7 @@ void do_page_fault(unsigned long address, struct pt_regs *regs) struct mm_struct *mm = tsk->mm; int sig, si_code = SEGV_MAPERR; unsigned int write = 0, exec = 0, mask; - vm_fault_t fault; /* handle_mm_fault() output */ + vm_fault_t fault = VM_FAULT_ERROR; /* handle_mm_fault() output */ unsigned int flags; /* handle_mm_fault() input */ /* @@ -155,6 +155,9 @@ void do_page_fault(unsigned long address, struct pt_regs *regs) } } +bad_area: + up_read(&mm->mmap_sem); + /* * Major/minor page fault accounting * (in case of retry we only land here once) @@ -173,13 +176,9 @@ void do_page_fault(unsigned long address, struct pt_regs *regs) } /* Normal return path: fault Handled Gracefully */ - up_read(&mm->mmap_sem); return; } -bad_area: - up_read(&mm->mmap_sem); - if (!user_mode(regs)) goto no_context; -- 2.7.4