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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id F0123C433F5 for ; Tue, 14 Dec 2021 15:41:03 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5ED366B0071; Tue, 14 Dec 2021 10:40:53 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 59C8B6B0073; Tue, 14 Dec 2021 10:40:53 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4645C6B0074; Tue, 14 Dec 2021 10:40:53 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.a.hostedemail.com [64.99.140.24]) by kanga.kvack.org (Postfix) with ESMTP id 36BD36B0071 for ; Tue, 14 Dec 2021 10:40:53 -0500 (EST) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay12.hostedemail.com (Postfix) with ESMTP id 0C05312070D for ; Tue, 14 Dec 2021 15:40:43 +0000 (UTC) X-FDA: 78916812366.05.1CE3740 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf08.hostedemail.com (Postfix) with ESMTP id 496BF160007 for ; Tue, 14 Dec 2021 15:40:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; 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; bh=DP7R5DQlRBuwKxAcekVF/e0Cj/7RMiSBN5vbq+wyWeY=; b=nQRaDyHAbRjSXMilHileHFVTOl W98orjLaE9WRiJVUXJ3wC7zh8okI+Go27Xp/k7uI0yz+mZEIkFbRyxVl4DSS1ZG0Mp+awPJpMYfHY LXkzmSK29bKyxXz/n/qTmaZNjtI7DFhl7Bh4qM7+VLJLF2YUsggkl7zC2d0JsM3amVPnA9ay1PL3v 91gTgh3+rzRVae1v90xpW3ySE43cn3ukT+pWG2PimwNctXf9yrrxnNCEJhFigoti3TDq8iOzDmreM jok5306ShlfiSR9NmhONLA+t6CpLjNbnPj51Kl1eIQ5AwpC1CRl6DaI84ZWWZ9T8gObaGjiR7kQRA nPSSWXqw==; Received: from hch by bombadil.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mx9uu-00Ej1C-74; Tue, 14 Dec 2021 15:40:36 +0000 Date: Tue, 14 Dec 2021 07:40:36 -0800 From: Christoph Hellwig To: Shiyang Ruan Cc: linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, nvdimm@lists.linux.dev, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, djwong@kernel.org, dan.j.williams@intel.com, david@fromorbit.com, hch@infradead.org, jane.chu@oracle.com Subject: Re: [PATCH v8 1/9] dax: Use percpu rwsem for dax_{read,write}_lock() Message-ID: References: <20211202084856.1285285-1-ruansy.fnst@fujitsu.com> <20211202084856.1285285-2-ruansy.fnst@fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211202084856.1285285-2-ruansy.fnst@fujitsu.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Rspamd-Queue-Id: 496BF160007 X-Stat-Signature: xib83iedy9ob9c73myekuhaiy99uebh1 Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=infradead.org header.s=bombadil.20210309 header.b=nQRaDyHA; dmarc=none; spf=none (imf08.hostedemail.com: domain of BATV+86a4492529da8568e983+6687+infradead.org+hch@bombadil.srs.infradead.org has no SPF policy when checking 198.137.202.133) smtp.mailfrom=BATV+86a4492529da8568e983+6687+infradead.org+hch@bombadil.srs.infradead.org X-Rspamd-Server: rspam11 X-HE-Tag: 1639496438-119036 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: On Thu, Dec 02, 2021 at 04:48:48PM +0800, Shiyang Ruan wrote: > In order to introduce dax holder registration, we need a write lock for > dax. Change the current lock to percpu_rw_semaphore and introduce a > write lock for registration. Why do we need to change the existing, global locking for that? What is the impact of this to benchmarks? Also if we stop using srcu protection, we should be able to get rid of grace periods or RCU frees.