From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753980AbZIRMbZ (ORCPT ); Fri, 18 Sep 2009 08:31:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753321AbZIRMbZ (ORCPT ); Fri, 18 Sep 2009 08:31:25 -0400 Received: from viefep12-int.chello.at ([62.179.121.32]:58786 "EHLO viefep12-int.chello.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752628AbZIRMbY (ORCPT ); Fri, 18 Sep 2009 08:31:24 -0400 X-SourceIP: 213.93.53.227 Subject: Re: [PATCH 0/2]: Get perf counters working on D-cache aliasing cpus. From: Peter Zijlstra To: David Miller Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, jens.axboe@oracle.com In-Reply-To: <20090908.051045.26522683.davem@davemloft.net> References: <20090908.051045.26522683.davem@davemloft.net> Content-Type: text/plain Date: Fri, 18 Sep 2009 14:31:36 +0200 Message-Id: <1253277096.8439.127.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2009-09-08 at 05:10 -0700, David Miller wrote: > With Jen's Axboe's basic sparc counter patch in my tree I started > playing with it on sparc64. Turns out it won't work on anything > pre-Niagara. > > The issue is D-cache aliasing between the kernel side mapping > and the user side mapping of the perf event ring buffer. > > The following two patches attempt to address this issue and > are working properly on my test machine. Dave, Ingo just reminded me that we might want to do splice support for perf stuff. My plan was to have the splice thing allocate a new page, flip with a filled one from the buffer and send the filled one down to the splice consumer. Now having vmap'ed all that complicates stuff enourmously. Would it also work if we use order-1 pages on your platform instead of order-0, so that they are properly aligned for the d-cache?