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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 02458C2D0C9 for ; Fri, 13 Dec 2019 21:44:42 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7CEF524679 for ; Fri, 13 Dec 2019 21:44:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="bxgbR8br" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7CEF524679 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B0BE08E0012; Fri, 13 Dec 2019 13:21:39 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id ABB398E0001; Fri, 13 Dec 2019 13:21:39 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9AA1F8E0012; Fri, 13 Dec 2019 13:21:39 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0066.hostedemail.com [216.40.44.66]) by kanga.kvack.org (Postfix) with ESMTP id 828C58E0001 for ; Fri, 13 Dec 2019 13:21:39 -0500 (EST) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id 352332464 for ; Fri, 13 Dec 2019 18:21:39 +0000 (UTC) X-FDA: 76260936318.12.uncle83_2b6ad77011f2c X-HE-Tag: uncle83_2b6ad77011f2c X-Filterd-Recvd-Size: 2414 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf22.hostedemail.com (Postfix) with ESMTP for ; Fri, 13 Dec 2019 18:21:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=2vnqL1NXc+4HvKs7uRYe8kQq6mPd6Wqr63sLnfqeViM=; b=bxgbR8br7zSmTcTw4ibQhfxdg FawEwe+zE5GDbAXh8FxTWw5j6MgX9j9DgEEM+fQU38WO3dL7S669czxRT3laXUnllRlXJeCkQD7Pp XJo5ut+r9hKBqW+akOlUV6pi96lOa5+O5YgChp1iuQrXhYZ+oQKDJ0Ryt6Gm3cGBhCSM0CXbSoqSH YyIMNDPXdkSWfZSfcy3t89g8R3umh2s1d6qjA4gAZofk/rY1H1VjrrnWB8qmPgmVS6knLOR4gXN/p uBW7PP5+WKqkNCFlBk6f1aUtzQKWRw8gDBr0Wr2Z1MuSvjnkog6ftqBxsCJtlDLGzfQIa8OyQEaIo SB62MrwLQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1ifpZI-0006lH-C8; Fri, 13 Dec 2019 18:21:36 +0000 Date: Fri, 13 Dec 2019 10:21:36 -0800 From: Matthew Wilcox To: "Kirill A. Shutemov" Cc: linux-mm@kvack.org Subject: Re: Splitting the mmap_sem Message-ID: <20191213182136.GX32169@bombadil.infradead.org> References: <20191203222147.GV20752@bombadil.infradead.org> <20191212142457.zqp4mawjz7frpyvk@box> <20191212154002.GR32169@bombadil.infradead.org> <20191212154613.qrfsqrgb24sj6fcx@box> <20191213143333.GW32169@bombadil.infradead.org> <20191213180626.aj5rper5kpjotbwi@box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191213180626.aj5rper5kpjotbwi@box> User-Agent: Mutt/1.12.1 (2019-06-15) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Dec 13, 2019 at 09:06:26PM +0300, Kirill A. Shutemov wrote: > On Fri, Dec 13, 2019 at 06:33:33AM -0800, Matthew Wilcox wrote: > > Ah. Well, we can skip the synchronize_rcu() step if the mm_struct has zero > > or one mm_users. That should avoid a slowdown for mmap/munmap. > > I may work. But I'm not sure how it will work with remote mm accesses. > Like with /proc/ interfaces or ptrace. Those users call mmget() which increases mm_users. See m_start() in fs/proc/task_mmu.c.