Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759450AbZJGP3c (ORCPT ); Wed, 7 Oct 2009 11:29:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759445AbZJGP3c (ORCPT ); Wed, 7 Oct 2009 11:29:32 -0400 Received: from smtp2.ultrahosting.com ([74.213.174.253]:35274 "EHLO smtp.ultrahosting.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1759308AbZJGP3b (ORCPT ); Wed, 7 Oct 2009 11:29:31 -0400 Date: Wed, 7 Oct 2009 11:05:42 -0400 (EDT) From: Christoph Lameter X-X-Sender: cl@gentwo.org To: Mathieu Desnoyers cc: Peter Zijlstra , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Pekka Enberg , Tejun Heo , Mel Gorman , mingo@elte.hu Subject: Re: [this_cpu_xx V5 19/19] SLUB: Experimental new fastpath w/o interrupt disable In-Reply-To: <20091007150257.GA8508@Krystal> Message-ID: References: <20091006233654.815079668@gentwo.org> <20091006233733.153341605@gentwo.org> <20091007025440.GB4664@Krystal> <1254906707.26976.225.camel@twins> <20091007124628.GB27363@Krystal> <20091007150257.GA8508@Krystal> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1023 Lines: 24 On Wed, 7 Oct 2009, Mathieu Desnoyers wrote: > Usually, when preemption is disabled, the scheduler restrain from > executing. *Now the important point*: the criterion that bounds the > maximum amount of time before the scheduler will re-check for pending > preemption is when preempt_enable() will re-activate preemption. Which creates additional overhead in the allocator. > But because you run preempt_enable with interrupts off, the scheduler > check is not done. And it's not done when interrupts are re-activated > neither. Ok so we should be moving the preempt_enable after the irq enable. Then we will call into the scheduler at the end of the slow path. This may add significantly more overhead that we had before when we simply disabled and enabled interrupts... -- 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/