From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934522Ab3HJQJl (ORCPT ); Sat, 10 Aug 2013 12:09:41 -0400 Received: from terminus.zytor.com ([198.137.202.10]:32967 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934374Ab3HJQJg (ORCPT ); Sat, 10 Aug 2013 12:09:36 -0400 Message-ID: <5206659F.9070705@zytor.com> Date: Sat, 10 Aug 2013 09:09:03 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Mike Galbraith CC: Andi Kleen , linux-kernel@vger.kernel.org, x86@kernel.org, mingo@kernel.org, torvalds@linux-foundation.org Subject: Re: Re-tune x86 uaccess code for PREEMPT_VOLUNTARY References: <1376089460-5459-1-git-send-email-andi@firstfloor.org> <5205C4BB.6020003@zytor.com> <1376114128.5332.17.camel@marge.simpson.net> In-Reply-To: <1376114128.5332.17.camel@marge.simpson.net> X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/09/2013 10:55 PM, Mike Galbraith wrote: >> >> Now, here is a bigger question: shouldn't we be deprecating/getting rid >> of PREEMPT_VOUNTARY in favor of PREEMPT? > > I sure hope not, PREEMPT munches throughput. If you need PREEMPT, seems > to me what you _really_ need is PREEMPT_RT (the real deal), so > eventually depreciating PREEMPT makes more sense to me. > Do you have any quantification of "munches throughput?" It seems odd that it would be worse than polling for preempt all over the kernel, but perhaps the additional locking is what costs. -hpa