From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751116AbXBNXqs (ORCPT ); Wed, 14 Feb 2007 18:46:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751129AbXBNXqs (ORCPT ); Wed, 14 Feb 2007 18:46:48 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:40987 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751116AbXBNXqr (ORCPT ); Wed, 14 Feb 2007 18:46:47 -0500 Date: Thu, 15 Feb 2007 00:44:17 +0100 From: Ingo Molnar To: Linus Torvalds Cc: Linux Kernel Mailing List , Arjan van de Ven , Christoph Hellwig , Andrew Morton , Alan Cox , Ulrich Drepper , Zach Brown , Evgeniy Polyakov , "David S. Miller" , Benjamin LaHaise , Suparna Bhattacharya , Davide Libenzi , Thomas Gleixner Subject: Re: [patch 05/11] syslets: core code Message-ID: <20070214234417.GA16332@elte.hu> References: <20070213142035.GF638@elte.hu> <20070214220948.GA3790@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -5.3 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-5.3 required=5.9 tests=ALL_TRUSTED,BAYES_00 autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Linus Torvalds wrote: > > case. (but with some crazier hacks i got the one-shot atom overhead > > [compared to a simple synchronous null syscall] to below 10 nsecs, > > so there's room in there for further optimizations. Our current null > > syscall latency is around ~150 nsecs.) > > You are not counting the whole setup cost there, then, because your > setup cost is going to be at a minimum more expensive than the null > system call. hm, this one-time cost was never on my radar. [ It's really dwarved by other startup costs (a single fork() takes 100 usecs, an exec() takes 800 usecs.) ] In any case, we can delay this cost into the first cachemiss, or can eliminate it by making it a globally pooled thing. It does not seem like a big issue. Ingo