From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761580AbXGPJpT (ORCPT ); Mon, 16 Jul 2007 05:45:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756014AbXGPJpH (ORCPT ); Mon, 16 Jul 2007 05:45:07 -0400 Received: from cantor2.suse.de ([195.135.220.15]:57784 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755046AbXGPJpF (ORCPT ); Mon, 16 Jul 2007 05:45:05 -0400 Date: Mon, 16 Jul 2007 11:45:03 +0200 From: Nick Piggin To: Ingo Molnar Cc: Andi Kleen , Linus Torvalds , Linux Kernel Mailing List Subject: Re: [rfc][patch 2/2] x86_64: FIFO ticket spinlocks Message-ID: <20070716094503.GC21464@wotan.suse.de> References: <20070716045932.GA19914@wotan.suse.de> <20070716050134.GB19914@wotan.suse.de> <20070716092646.GA18423@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070716092646.GA18423@elte.hu> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 16, 2007 at 11:26:46AM +0200, Ingo Molnar wrote: > > * Nick Piggin wrote: > > > [...] trylock is more significantly slower, but they are relatively > > rare. > > trylock is the main thing that the spinlock debugging code uses, and > SPINLOCK_DEBUG is frequently enabled by distro kernels. OTOH, the cost > looks like to be +5 instructions, right? Still ... Which trylocks do you mean? The lockbreak spinlocks use trylock, but those are not used with the ticket version. I wouldn't be against adding an option between either of the lock types, if there was value in it. But I would like to default ticket locks to "y", at least in -rc kernels, in order to see if performance goes down anywhere.