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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 BE2D9C43381 for ; Thu, 4 Mar 2021 07:45:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9523A64F10 for ; Thu, 4 Mar 2021 07:45:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234459AbhCDHog (ORCPT ); Thu, 4 Mar 2021 02:44:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60102 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234401AbhCDHoW (ORCPT ); Thu, 4 Mar 2021 02:44:22 -0500 Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [IPv6:2a0a:51c0:0:12e:520::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 28904C061574; Wed, 3 Mar 2021 23:43:42 -0800 (PST) Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1lHie1-0007Sy-JD; Thu, 04 Mar 2021 08:43:37 +0100 Date: Thu, 4 Mar 2021 08:43:37 +0100 From: Florian Westphal To: Mark Tomlinson Cc: pablo@netfilter.org, kadlec@netfilter.org, fw@strlen.de, netfilter-devel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] Revert "netfilter: x_tables: Update remaining dereference to RCU" Message-ID: <20210304074337.GH17911@breakpoint.cc> References: <20210304013116.8420-1-mark.tomlinson@alliedtelesis.co.nz> <20210304013116.8420-2-mark.tomlinson@alliedtelesis.co.nz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210304013116.8420-2-mark.tomlinson@alliedtelesis.co.nz> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Mark Tomlinson wrote: > This reverts commit 443d6e86f821a165fae3fc3fc13086d27ac140b1. > > This (and the following) patch basically re-implemented the RCU > mechanisms of patch 784544739a25. That patch was replaced because of the > performance problems that it created when replacing tables. Now, we have > the same issue: the call to synchronize_rcu() makes replacing tables > slower by as much as an order of magnitude. > > See https://lore.kernel.org/patchwork/patch/151796/ for why using RCU is > not a good idea. Please don't add links for the rationale.