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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 BBE7FC47095 for ; Mon, 7 Jun 2021 12:39:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A5B9060FEE for ; Mon, 7 Jun 2021 12:39:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230242AbhFGMlj (ORCPT ); Mon, 7 Jun 2021 08:41:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:57664 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230198AbhFGMlj (ORCPT ); Mon, 7 Jun 2021 08:41:39 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9E4EB611C0; Mon, 7 Jun 2021 12:39:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1623069588; bh=Zjlt55KMswnh9QqGbwu3mbMkjV9KlBZv59wVoY8s6lo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FdktRMOhRdqo8mujxRH7TjuCV5c13oGNlAG8M+c43vJUQwVFxmhDvlaltSIq2PdsU x4bExb/WGg371tivgQcy3STYNmtaUq2RKKIvRjV5g/qyrQhWwFoHRNHJYbZR/o1zEy vox2wktMQMExdVNmV5EVzN2lc8zOLzJRdFyghS/A= Date: Mon, 7 Jun 2021 14:39:45 +0200 From: Greg KH To: Jason Gunthorpe Cc: Leon Romanovsky , Doug Ledford , Kees Cook , Nathan Chancellor , Adit Ranadive , Ariel Elior , Christian Benvenuti , clang-built-linux@googlegroups.com, Dennis Dalessandro , Devesh Sharma , Gal Pressman , linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, Michal Kalderon , Mike Marciniszyn , Mustafa Ismail , Naresh Kumar PBS , Nelson Escobar , Nick Desaulniers , Potnuri Bharat Teja , Selvin Xavier , Shiraz Saleem , VMware PV-Drivers , Yishai Hadas , Zhu Yanjun Subject: Re: [PATCH rdma-next v1 10/15] RDMA/cm: Use an attribute_group on the ib_port_attribute intead of kobj's Message-ID: References: <00e578937f557954d240bc0856f45b3f752d6cba.1623053078.git.leonro@nvidia.com> <20210607121411.GC1002214@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210607121411.GC1002214@nvidia.com> Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On Mon, Jun 07, 2021 at 09:14:11AM -0300, Jason Gunthorpe wrote: > On Mon, Jun 07, 2021 at 12:25:03PM +0200, Greg KH wrote: > > On Mon, Jun 07, 2021 at 11:17:35AM +0300, Leon Romanovsky wrote: > > > From: Jason Gunthorpe > > > > > > This code is trying to attach a list of counters grouped into 4 groups to > > > the ib_port sysfs. Instead of creating a bunch of kobjects simply express > > > everything naturally as an ib_port_attribute and add a single > > > attribute_groups list. > > > > > > Remove all the naked kobject manipulations. > > > > Much nicer. > > > > But why do you need your counters to be atomic in the first place? What > > are they counting that requires this? > > The write side of the counter is being updated from concurrent kernel > threads without locking, so this is an atomic because the write side > needs atomic_add(). So the atomic write forces a lock :( > Making them a naked u64 will cause significant corruption on the write > side, and packet counters that are not accurate after quiescence are > not very useful things. How "accurate" do these have to be? And have you all tried them? I'm pushing back here as I see a lot of atomics used for debugging statistics for no good reason all over the place. Especially when userspace just does not care. thanks, greg k-h