Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754022AbXJBGI7 (ORCPT ); Tue, 2 Oct 2007 02:08:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751243AbXJBGIw (ORCPT ); Tue, 2 Oct 2007 02:08:52 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:55519 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751164AbXJBGIv (ORCPT ); Tue, 2 Oct 2007 02:08:51 -0400 Date: Tue, 2 Oct 2007 08:08:48 +0200 From: Ingo Molnar To: David Schwartz Cc: linux-kernel@vger.kernel.org Subject: Re: Network slowdown due to CFS Message-ID: <20071002060848.GB18588@elte.hu> References: <20071001173159.GB2492@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7-deb -1.5 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 Content-Length: 896 Lines: 22 * David Schwartz wrote: > > (user-space spinlocks are broken beyond words for anything but > > perhaps SCHED_FIFO tasks.) > > User-space spinlocks are broken so spinlocks can only be implemented > in kernel-space? Even if you use the kernel to schedule/unschedule the > tasks, you still have to spin in user-space. user-space spinlocks (in anything but SCHED_FIFO tasks) are pretty broken because they waste CPU time. (not as broken as yield, because "wasting CPU time" is a more deterministic act, but still broken) Could you cite a single example where user-space spinlocks are technically the best solution? Ingo - 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/