From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH] percpu: add optimized generic percpu accessors Date: Tue, 20 Jan 2009 15:25:50 +0900 Message-ID: <49756E6E.2060409@kernel.org> References: <20090115183942.GA6325@elte.hu> <200901170827.33729.rusty@rustcorp.com.au> <20090116220832.GB20653@elte.hu> <200901201328.24605.rusty@rustcorp.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Ingo Molnar , Herbert Xu , akpm@linux-foundation.org, hpa@zytor.com, brgerst@gmail.com, ebiederm@xmission.com, cl@linux-foundation.org, travis@sgi.com, linux-kernel@vger.kernel.org, steiner@sgi.com, hugh@veritas.com, "David S. Miller" , netdev@vger.kernel.org, Mathieu Desnoyers To: Rusty Russell Return-path: Received: from hera.kernel.org ([140.211.167.34]:59346 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752890AbZATG00 (ORCPT ); Tue, 20 Jan 2009 01:26:26 -0500 In-Reply-To: <200901201328.24605.rusty@rustcorp.com.au> Sender: netdev-owner@vger.kernel.org List-ID: Rusty Russell wrote: > The generic versions Tejun posted are not softirq safe, so not > suitable for network counters. To figure out what semantics we > really want we need to we must audit the users; I'm sorry I haven't > finished that task (and won't until after the conference). No, they're not. They're preempt safe as mentioned in the comment and is basically just generalization of the original x86 versions used by x86_64 on SMP before pda and percpu areas were merged. I agree that it's something very close to local_t and it would be nice to see those somehow unified (and I have patches which make use of local_t in my queue waiting for dynamic percpu allocation). Another question to ask is whether to keep using separate interfaces for static and dynamic percpu variables or migrate to something which can take both. Thanks. -- tejun