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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 083D3C433F5 for ; Fri, 28 Jan 2022 13:20:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349036AbiA1NUA (ORCPT ); Fri, 28 Jan 2022 08:20:00 -0500 Received: from server.lespinasse.org ([63.205.204.226]:45043 "EHLO server.lespinasse.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348670AbiA1NTK (ORCPT ); Fri, 28 Jan 2022 08:19:10 -0500 DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=lespinasse.org; i=@lespinasse.org; q=dns/txt; s=srv-52-ed; t=1643375407; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : from; bh=N1bCyCqlqCPmn3u4dr/qGIvPJEOlMd8KVKMJcaELgEw=; b=GcBReqmwDZ82aVnHS0hCCWXYruQ1qrdcFPqUv1QkU6UoqgPLM+nRmvNS0Y8AYDNay6K1/ WrF/45/SfCMN4X4Bw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lespinasse.org; i=@lespinasse.org; q=dns/txt; s=srv-52-rsa; t=1643375407; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : from; bh=N1bCyCqlqCPmn3u4dr/qGIvPJEOlMd8KVKMJcaELgEw=; b=0fIaqi5/e6TyDkW5DpsQrirQBlbVLQ6vD67HM9rQxnG/ldkbMS/1aO1AiQET+/+D1Wxp3 Vo3HWduaw/24aWGBGAOG7sRUAqxQa9gvY5TqSrmEIbhtiNXIFrxZzvVmTqly4Issy95x4JZ XpUoZZcE5SnkHhoHB10UfCAVkkVE2c9veNH+HcRiGCIJE7VAJr7oiNuou1QLzhuQ9Algvkf igQLboMXPIsg3bvd3gxPJfjO6ges3d0MKFpLCjlXZt+yUAlXlhwjVP8IkEAW9tPE7bRVYLM kP474IHw4IXNCpCJ02BnlHqMo47/ZINoDZlC8r5J6BYzN2BgvHhe5CoZbTdA== Received: from zeus.lespinasse.org (zeus.lespinasse.org [IPv6:fd00::150:0]) by server.lespinasse.org (Postfix) with ESMTPS id 33BE8160AAE; Fri, 28 Jan 2022 05:10:07 -0800 (PST) Received: by zeus.lespinasse.org (Postfix, from userid 1000) id 19D0820FB1; Fri, 28 Jan 2022 05:10:07 -0800 (PST) From: Michel Lespinasse To: Linux-MM , linux-kernel@vger.kernel.org, Andrew Morton Cc: kernel-team@fb.com, Laurent Dufour , Jerome Glisse , Peter Zijlstra , Michal Hocko , Vlastimil Babka , Davidlohr Bueso , Matthew Wilcox , Liam Howlett , Rik van Riel , Paul McKenney , Song Liu , Suren Baghdasaryan , Minchan Kim , Joel Fernandes , David Rientjes , Axel Rasmussen , Andy Lutomirski , Michel Lespinasse Subject: [PATCH v2 28/35] mm: disable speculative faults for single threaded user space Date: Fri, 28 Jan 2022 05:09:59 -0800 Message-Id: <20220128131006.67712-29-michel@lespinasse.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20220128131006.67712-1-michel@lespinasse.org> References: <20220128131006.67712-1-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 | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 6ba109413396..d6f8d4967c49 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1328,6 +1328,13 @@ 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) @@ -1362,7 +1369,9 @@ 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