Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751096AbWIKKtv (ORCPT ); Mon, 11 Sep 2006 06:49:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751085AbWIKKtv (ORCPT ); Mon, 11 Sep 2006 06:49:51 -0400 Received: from mx1.redhat.com ([66.187.233.31]:956 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S1750997AbWIKKtu (ORCPT ); Mon, 11 Sep 2006 06:49:50 -0400 From: David Howells In-Reply-To: <20060909054642.GA8859@elte.hu> References: <20060909054642.GA8859@elte.hu> <20060906125626.GA3718@elte.hu> <20060906094301.GA8694@elte.hu> <1157507203.2222.11.camel@localhost> <20060905132530.GD9173@stusta.de> <20060901015818.42767813.akpm@osdl.org> <6260.1157470557@warthog.cambridge.redhat.com> <8430.1157534853@warthog.cambridge.redhat.com> <13982.1157545856@warthog.cambridge.redhat.com> <17274.1157553962@warthog.cambridge.redhat.com> To: Ingo Molnar Cc: David Howells , john stultz , Adrian Bunk , Andrew Morton , Arjan van de Ven , linux-kernel@vger.kernel.org, Jeff Garzik , netdev@vger.kernel.org, Thomas Gleixner , Benjamin Herrenschmidt Subject: Re: [PATCH] FRV: do_gettimeofday() should no longer use tickadj X-Mailer: MH-E 8.0; nmh 1.1; GNU Emacs 22.0.50 Date: Mon, 11 Sep 2006 11:46:44 +0100 Message-ID: <9051.1157971604@warthog.cambridge.redhat.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1289 Lines: 30 Ingo Molnar wrote: > i cannot find Thomas' recent 2.6 one (Thomas, do you have a link to > it?), but i did one 5 years ago: > > http://people.redhat.com/mingo/irq-rewrite-patches/irq-cleanup-2.4.15-B1.bz2 > > in general it's a large but otherwise pretty dumb patch. I wrote my own patch to test this last Friday. I found that removing all the regs pointer passing from the interrupt code reduced interrupt entry with a warm cache by 1 cpu cycle out of 87, and interrupt exit by 19 cycles out of 99. I can't tell from that exactly how many instructions/memory accesses have been removed since the FRV permits two instructions to be executed in one cycle under some circumstances, and two registers to be stored/loaded in one instruction. But the main gain in the exit path has to be due to recovery of the clobbered regs parameter due to a call inside a loop, possibly in handle_IRQ_event(). I'd expect i386 to do better in cycle reduction because it has fewer registers and so getting one back should gain more. David - 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/