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=-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 36874C433B4 for ; Fri, 30 Apr 2021 19:54:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 17E1E61476 for ; Fri, 30 Apr 2021 19:54:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233969AbhD3TzD (ORCPT ); Fri, 30 Apr 2021 15:55:03 -0400 Received: from server.lespinasse.org ([63.205.204.226]:56609 "EHLO server.lespinasse.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232454AbhD3Txh (ORCPT ); Fri, 30 Apr 2021 15:53:37 -0400 DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=lespinasse.org; i=@lespinasse.org; q=dns/txt; s=srv-14-ed; t=1619812353; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : from; bh=8JAcgap2Y6VBqeBYCFSL5shic9T9aRbFwbzzfMi53Zk=; b=cHUjMGrj2X1IDinPMY0+dKYe5adB499TJ7H+bfr7ETPsZilLoPfMVym38TQeMy1ziuWpJ F9gf1FUC9B6sDyRAQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lespinasse.org; i=@lespinasse.org; q=dns/txt; s=srv-14-rsa; t=1619812353; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : from; bh=8JAcgap2Y6VBqeBYCFSL5shic9T9aRbFwbzzfMi53Zk=; b=UOOGCy41woDuBjIDj9AxgKSCdxZe8jlgAyT+CGVtOzwTmo1GlRVsIqe2Zdz1vQCn5TA1M /JofEHwPBChM0jwFBGv0l1piRk7vawrDfwuf8LY+3xed2fTKScXpJPoombyg5uNGM7eV5ys xx3jPzEFN1dABh3CoMDkDS3TWTTz69MLk5zsxFvPx3xklT+UzFtYV9KZhNn5QP/dj3HJLuE oWD2jRpym5v+B+ektmeW8VK4vXJsA6jn/3xVM28w/qteRSICYJ9RWdZkWdfSooPqFR0JBEo CbTC/gyL58DqgVVo/N8uTUPO51ELndImk4v7llW3NZgVtzXawHqurgd+x5uA== Received: from zeus.lespinasse.org (zeus.lespinasse.org [10.0.0.150]) by server.lespinasse.org (Postfix) with ESMTPS id B03AB160361; Fri, 30 Apr 2021 12:52:33 -0700 (PDT) Received: by zeus.lespinasse.org (Postfix, from userid 1000) id A135219F524; Fri, 30 Apr 2021 12:52:33 -0700 (PDT) From: Michel Lespinasse To: Linux-MM , Linux-Kernel Cc: Laurent Dufour , Peter Zijlstra , Michal Hocko , Matthew Wilcox , Rik van Riel , Paul McKenney , Andrew Morton , Suren Baghdasaryan , Joel Fernandes , Andy Lutomirski , Michel Lespinasse Subject: [PATCH 25/29] mm: disable speculative faults for single threaded user space Date: Fri, 30 Apr 2021 12:52:26 -0700 Message-Id: <20210430195232.30491-26-michel@lespinasse.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210430195232.30491-1-michel@lespinasse.org> References: <20210430195232.30491-1-michel@lespinasse.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Performance tuning: single threaded userspace does not benefit from speculative page faults, so we turn them off to avoid any related (small) extra overheads. Signed-off-by: Michel Lespinasse --- arch/x86/mm/fault.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 463061186827..b5c21585e35f 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1321,6 +1321,14 @@ void do_user_addr_fault(struct pt_regs *regs, #endif #ifdef CONFIG_SPECULATIVE_PAGE_FAULT + + /* + * No need to try speculative faults for kernel or + * single threaded user space. + */ + if (!(flags & FAULT_FLAG_USER) || atomic_read(&mm->mm_users) == 1) + goto no_spf; + count_vm_event(SPF_ATTEMPT); seq = mmap_seq_read_start(mm); if (seq & 1) @@ -1353,7 +1361,9 @@ void do_user_addr_fault(struct pt_regs *regs, spf_abort: count_vm_event(SPF_ABORT); -#endif +no_spf: + +#endif /* CONFIG_SPECULATIVE_PAGE_FAULT */ /* * Kernel-mode access to the user address space should only occur -- 2.20.1