From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261224AbVF2Oxw (ORCPT ); Wed, 29 Jun 2005 10:53:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261237AbVF2Oxw (ORCPT ); Wed, 29 Jun 2005 10:53:52 -0400 Received: from ms-smtp-04.nyroc.rr.com ([24.24.2.58]:9918 "EHLO ms-smtp-04.nyroc.rr.com") by vger.kernel.org with ESMTP id S261224AbVF2Oxu convert rfc822-to-8bit (ORCPT ); Wed, 29 Jun 2005 10:53:50 -0400 Date: Wed, 29 Jun 2005 10:53:10 -0400 (EDT) From: Steven Rostedt X-X-Sender: rostedt@localhost.localdomain Reply-To: rostedt@goodmis.org To: =?iso-8859-1?Q?J=F6rn?= Engel cc: Denis Vlasenko , Arjan van de Ven , Jens Axboe , linux-kernel@vger.kernel.org Subject: Re: kmalloc without GFP_xxx? In-Reply-To: <20050629142317.GB2130@wohnheim.fh-wedel.de> Message-ID: References: <200506291402.18064.vda@ilport.com.ua> <1120045024.3196.34.camel@laptopd505.fenrus.org> <200506291714.32990.vda@ilport.com.ua> <20050629142317.GB2130@wohnheim.fh-wedel.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 29 Jun 2005, Jörn Engel wrote: > On Wed, 29 June 2005 17:14:32 +0300, Denis Vlasenko wrote: > > > > This is why I always use _irqsave. Less error prone. > > And locking is a very easy to get 'slightly' wrong, thus > > I trade 0.1% of performance for code simplicity. > > But sometimes you get lucky and trade 100ms latency for code > simplicity. Of course, the audio people don't mind anymore, now that > we have all sorts of realtime patches. Everyone's happy! > God! If you are holding a spin_lock for 100ms, something is terribly wrong, especialy since you better not schedule holding that spin_lock. Spinlocks are _suppose_ to be for quick things. The difference in latency between a *_lock and *_lock_irqsave only effects UP, on SMP both will give the same latency, since another CPU might be busy spinning while waiting for that lock, heck, on SMP the latency of *_lock can actually be higher, since, as I already said, the other CPU will even have to wait while the CPU that has the lock is servicing interrupts. Although I must say that with all the realtime patches I'm happy :-) -- Steve