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 5210BC433B4 for ; Wed, 7 Apr 2021 01:45:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E9CC6610CE for ; Wed, 7 Apr 2021 01:45:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E9CC6610CE 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 A4A458D0002; Tue, 6 Apr 2021 21:45:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 983DF6B0089; Tue, 6 Apr 2021 21:45:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 53E826B0089; Tue, 6 Apr 2021 21:45:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0211.hostedemail.com [216.40.44.211]) by kanga.kvack.org (Postfix) with ESMTP id 226F26B0082 for ; Tue, 6 Apr 2021 21:45:07 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id D96518249980 for ; Wed, 7 Apr 2021 01:45:06 +0000 (UTC) X-FDA: 78003877812.24.6AF6E80 Received: from server.lespinasse.org (server.lespinasse.org [63.205.204.226]) by imf01.hostedemail.com (Postfix) with ESMTP id F33295001528 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=1617759902; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : from; bh=45X0hICb7YyLurpFubxOZ+gBL34g/MPyB7oW/aDWSiM=; b=Ezxxe9KDQsCFhUHAu9I8tXq3tzT+ETWkukiiTwYTUJy0+mEiULNUYHD1E3OGsCJ2WVgK+ 6sVgt4/DR/scN5rDA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lespinasse.org; i=@lespinasse.org; q=dns/txt; s=srv-11-rsa; t=1617759902; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : from; bh=45X0hICb7YyLurpFubxOZ+gBL34g/MPyB7oW/aDWSiM=; b=OIBfjJ1bYm37SwxCxTZxWBm6/JHot+77xHwF5V/8sYbQYkkLwxhE3KbqcmCsOgfilCuOe kPpyZrn7Wf5hzU3ilIC1gXGABhNrY4ctFg9vLpbXQhB1MQ3fIfDvSVlFjbQDpnshhEhCE2W jSgP0RqvYexT8jbDex/isE6RL/ElD3hYo1qqrkUe4YxlrI17K1OC3DDgjSOe4QxyDePMiNS ByZf0vq9GK578fKtRJ3Q9uSgRs1RMCV7tyWz+2ukebX+vT6OkKeM3iUxIQtur5QmxepoA+U J97XdXAFSjABk9diVgwmNmv0b2H4KQq+SRvewPy4ziSva9rDbfiYKXbB6KLw== Received: from zeus.lespinasse.org (zeus.lespinasse.org [IPv6:fd00::150:0]) by server.lespinasse.org (Postfix) with ESMTPS id 850A616023A; Tue, 6 Apr 2021 18:45:02 -0700 (PDT) Received: by zeus.lespinasse.org (Postfix, from userid 1000) id 773DB19F31D; Tue, 6 Apr 2021 18:45:02 -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 05/37] mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT Date: Tue, 6 Apr 2021 18:44:30 -0700 Message-Id: <20210407014502.24091-6-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: rspam03 X-Rspamd-Queue-Id: F33295001528 X-Stat-Signature: mbzqehcah57wgnom5yf8tmshcmq7c9qc Received-SPF: none (lespinasse.org>: No applicable sender policy available) receiver=imf01; identity=mailfrom; envelope-from=""; helo=server.lespinasse.org; client-ip=63.205.204.226 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617759905-480571 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: This configuration variable will be used to build the code needed to handle speculative page fault. This is enabled by default on supported architectures with SMP and MMU se= t. The architecture support is needed since the speculative page fault handl= er is called from the architecture's page faulting code, and some code has t= o be added there to try speculative fault handling first. Signed-off-by: Michel Lespinasse --- mm/Kconfig | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/mm/Kconfig b/mm/Kconfig index 24c045b24b95..322bda319dea 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -872,4 +872,26 @@ config MAPPING_DIRTY_HELPERS config KMAP_LOCAL bool =20 +config ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT + def_bool n + +config SPECULATIVE_PAGE_FAULT + bool "Speculative page faults" + default y + depends on ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT && MMU && SMP + help + Try to handle user space page faults without holding the mmap lock. + + Instead of blocking writers through the use of mmap lock, + the page fault handler merely verifies, at the end of the page + fault, that no writers have been running concurrently with it. + + In high concurrency situations, the speculative fault handler + gains a throughput advantage by avoiding having to update the + mmap lock reader count. + + If the check fails due to a concurrent writer, or due to hitting + an unsupported case, the fault handler falls back to classical + processing using the mmap read lock. + endmenu --=20 2.20.1