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=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 72973C433B4 for ; Wed, 7 Apr 2021 01:46:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1AC62613A7 for ; Wed, 7 Apr 2021 01:46:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1AC62613A7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=lespinasse.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 60FDB8E0001; Tue, 6 Apr 2021 21:45:12 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A25CA6B0092; Tue, 6 Apr 2021 21:45:11 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7145A8E0016; Tue, 6 Apr 2021 21:45:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0122.hostedemail.com [216.40.44.122]) by kanga.kvack.org (Postfix) with ESMTP id 1DA816B0087 for ; Tue, 6 Apr 2021 21:45:09 -0400 (EDT) Received: from smtpin33.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id D1013181AF5FD for ; Wed, 7 Apr 2021 01:45:08 +0000 (UTC) X-FDA: 78003877896.33.D3EC076 Received: from server.lespinasse.org (server.lespinasse.org [63.205.204.226]) by imf10.hostedemail.com (Postfix) with ESMTP id 856C240002C0 for ; Wed, 7 Apr 2021 01:45:05 +0000 (UTC) DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=lespinasse.org; i=@lespinasse.org; q=dns/txt; s=srv-11-ed; t=1617759903; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : from; bh=dxj+e2mCTN/mq8/QKyjl2SahvK7RHudQGhkISRnBVig=; b=+Q3LDhDV38Tl/5VVpqEc6k0vUGZdg8aC5vuZTmv9XW2HYt5SSVn8xVrXOLUhh39OTr4Yk BKC/hKD7DF5025fBQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lespinasse.org; i=@lespinasse.org; q=dns/txt; s=srv-11-rsa; t=1617759903; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : from; bh=dxj+e2mCTN/mq8/QKyjl2SahvK7RHudQGhkISRnBVig=; b=JZCFDV30/yXf6H5J+f3SdyNh3hYLqYl3vEW/Ni6crQkjRh6o64d2cKCZQ12mIdV86AgjG 0xb5dvncR9Q3KIcUxaTww6pmfH1dLtaCq1+ywsEV/VkJRKDmMqq2UPyWsGYMvmOB2h81Mps ZWcf0+Bkuo1o4Aul81AclAy77gUiuOhdyIRW9wyIF6E+BzIZARbKoxx0xNxmxbu11pF0uPI HpgNlVPPyxwfH5rbkK60cLgd+29R2XTs+4kyo2nRLVJ4eIM7XcMOQenuTzpR9GikW/t7IEy h18AfoPFjs2trfBmdlGX++FxPVo1dYiS2yW0X60gIkpTzML88X/k546hS3/A== Received: from zeus.lespinasse.org (zeus.lespinasse.org [10.0.0.150]) by server.lespinasse.org (Postfix) with ESMTPS id 59267160650; Tue, 6 Apr 2021 18:45:03 -0700 (PDT) Received: by zeus.lespinasse.org (Postfix, from userid 1000) id 4A03A19F31F; Tue, 6 Apr 2021 18:45:03 -0700 (PDT) From: Michel Lespinasse To: Linux-MM Cc: Laurent Dufour , Peter Zijlstra , Michal Hocko , Matthew Wilcox , Rik van Riel , Paul McKenney , Andrew Morton , Suren Baghdasaryan , Joel Fernandes , Rom Lemarchand , Linux-Kernel , Michel Lespinasse Subject: [RFC PATCH 33/37] mm: enable speculative fault handling only for multithreaded user space Date: Tue, 6 Apr 2021 18:44:58 -0700 Message-Id: <20210407014502.24091-34-michel@lespinasse.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210407014502.24091-1-michel@lespinasse.org> References: <20210407014502.24091-1-michel@lespinasse.org> MIME-Version: 1.0 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 856C240002C0 X-Stat-Signature: ftm63kxezwhmx1sjd43osq1oeey65d68 Received-SPF: none (lespinasse.org>: No applicable sender policy available) receiver=imf10; identity=mailfrom; envelope-from=""; helo=server.lespinasse.org; client-ip=63.205.204.226 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617759905-732151 Content-Transfer-Encoding: quoted-printable 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: 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 | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 48b86911a6df..b1a07ca82d59 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1318,6 +1318,10 @@ void do_user_addr_fault(struct pt_regs *regs, } #endif =20 + /* Only try spf for multithreaded user space faults. */ + if (!(flags & FAULT_FLAG_USER) || atomic_read(&mm->mm_users) =3D=3D 1) + goto no_spf; + count_vm_event(SPF_ATTEMPT); seq =3D mmap_seq_read_start(mm); if (seq & 1) @@ -1351,6 +1355,7 @@ void do_user_addr_fault(struct pt_regs *regs, =20 spf_abort: count_vm_event(SPF_ABORT); +no_spf: =20 /* * Kernel-mode access to the user address space should only occur --=20 2.20.1