Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757538AbYFPSSU (ORCPT ); Mon, 16 Jun 2008 14:18:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752987AbYFPSSM (ORCPT ); Mon, 16 Jun 2008 14:18:12 -0400 Received: from rv-out-0506.google.com ([209.85.198.224]:62656 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751633AbYFPSSL (ORCPT ); Mon, 16 Jun 2008 14:18:11 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references:x-google-sender-auth; b=qSLuJ9pKJ4qokH2195IXsji6DE8rmvdCdUh1ZYhnqrorVIy9p6Pa5IrLtsUsrT6ZLd KkOdwgqOFR++ALni3qBaOPwPUmkR33anUGW/B568r990N3L4KCgKyfzb8kwxW6dFuwV8 XTHdcPV+688Di0R57YIEEZpwCrFd32GRdnsf4= Message-ID: <84144f020806161118n70a876aeyb5ccac7b1e21d842@mail.gmail.com> Date: Mon, 16 Jun 2008 21:18:11 +0300 From: "Pekka Enberg" To: "Jens Axboe" Subject: Re: [PATCH 2/3] relay: Fix race condition which occurs when reading across CPUs. Cc: "Eduard - Gabriel Munteanu" , "Mathieu Desnoyers" , "Tom Zanussi" , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, righi.andrea@gmail.com In-Reply-To: <20080616164609.GM20851@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080613040958.4f52ee29@linux360.ro> <1213417601.8237.37.camel@charm-linux> <20080614181103.17617db1@linux360.ro> <20080616122249.GB18561@Krystal> <20080616162212.27a8c119@linux360.ro> <20080616164609.GM20851@kernel.dk> X-Google-Sender-Auth: 8c7a3e0988b78906 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1109 Lines: 24 Hi Jens, On Mon, Jun 16 2008, Eduard - Gabriel Munteanu wrote: >> In any case, if we use relay in a hot path, we are doing debugging, so >> a couple of atomic operations won't be a big problem. Along with >> setting affinity, this shouldn't be a problem. On Mon, Jun 16, 2008 at 7:46 PM, Jens Axboe wrote: > Ehm no, that is a completely false claim. Relay speed does matter, a > great deal. We rely heavily on eg blktrace being as ligt weight as > possible to capture millions of events in a very short time frame > without impacting performance too much. Relay is NOT just for debugging. > > So I completely agree with Mathieu here, and I'm not a big fan of the > proposed solution. OK, so we just document that fact that you're not supposed to read from different CPU and be done with that? Or do you have any alternative fix in mind? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/