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,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 195F6C433ED for ; Fri, 30 Apr 2021 19:53:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BB06861476 for ; Fri, 30 Apr 2021 19:53:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BB06861476 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 95CD46B0081; Fri, 30 Apr 2021 15:52:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 33D466B0074; Fri, 30 Apr 2021 15:52:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9077D6B009C; Fri, 30 Apr 2021 15:52:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0251.hostedemail.com [216.40.44.251]) by kanga.kvack.org (Postfix) with ESMTP id 415CA6B0080 for ; Fri, 30 Apr 2021 15:52:37 -0400 (EDT) Received: from smtpin38.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 030314FFA for ; Fri, 30 Apr 2021 19:52:37 +0000 (UTC) X-FDA: 78090080754.38.38E36A2 Received: from server.lespinasse.org (server.lespinasse.org [63.205.204.226]) by imf27.hostedemail.com (Postfix) with ESMTP id 8BBFC80192ED for ; Fri, 30 Apr 2021 19:52:11 +0000 (UTC) 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=45X0hICb7YyLurpFubxOZ+gBL34g/MPyB7oW/aDWSiM=; b=5gnptII9qFi2vooFljqITSE4K6KmNZmsZmUPuqA2aMK3ARQMebMw8B1ZPqFQY3ds9B1t2 IhTIiOxATX/AphyDA== 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=45X0hICb7YyLurpFubxOZ+gBL34g/MPyB7oW/aDWSiM=; b=D3rIm98jspzMJBMzKScap9IiDti8fm4LvQR4SgfW7kvabLrgbhZrxbLJrAf5SMZcI3Sj5 JNgjQhZfRHtA0ssRxK4rqcWQqNQYno/lv3EYRtp4IjbDAWCX6wkDXnYC+bQjKEzp4gTRRYn gfD/+gjMyeFu0OVJDY869fxTD7GebVa0YSAMoNtkKvifQ3Ero2ezc1mpuaBFMtJFzOYphYB G55SHqK9BMFKChPa/vhHCUs4RDHIs8uYd5tb4C88OxVErkXSgXU/aaSCE164Ky+YjPxltnc ey6wXUJ0vLUoy/ord59B2CZdz19w9q7g5Dci3Vyz1SaF8tlLzZ/hBvu3xwrg== Received: from zeus.lespinasse.org (zeus.lespinasse.org [10.0.0.150]) by server.lespinasse.org (Postfix) with ESMTPS id 2F30F160310; Fri, 30 Apr 2021 12:52:33 -0700 (PDT) Received: by zeus.lespinasse.org (Postfix, from userid 1000) id 2107F19F523; 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 06/29] mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT Date: Fri, 30 Apr 2021 12:52:07 -0700 Message-Id: <20210430195232.30491-7-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 X-Stat-Signature: h5af6si4k9gsyiiafjrce3f91werag75 X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 8BBFC80192ED Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=lespinasse.org header.s=srv-14-ed header.b=5gnptII9; dkim=pass header.d=lespinasse.org header.s=srv-14-rsa header.b=D3rIm98j; spf=pass (imf27.hostedemail.com: domain of walken@lespinasse.org designates 63.205.204.226 as permitted sender) smtp.mailfrom=walken@lespinasse.org; dmarc=pass (policy=none) header.from=lespinasse.org Received-SPF: none (lespinasse.org>: No applicable sender policy available) receiver=imf27; identity=mailfrom; envelope-from=""; helo=server.lespinasse.org; client-ip=63.205.204.226 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1619812331-453097 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