Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261534AbUJZXPI (ORCPT ); Tue, 26 Oct 2004 19:15:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261538AbUJZXPI (ORCPT ); Tue, 26 Oct 2004 19:15:08 -0400 Received: from fw.osdl.org ([65.172.181.6]:15331 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S261534AbUJZXPD (ORCPT ); Tue, 26 Oct 2004 19:15:03 -0400 Date: Tue, 26 Oct 2004 16:15:00 -0700 (PDT) From: Linus Torvalds To: Zachary Amsden cc: linux-kernel@vger.kernel.org, davej@codemonkey.org.uk, hpa@zytor.com Subject: Re: [PATCH] faster signal handling on x86 In-Reply-To: <417EC7BA.3050604@vmware.com> Message-ID: References: <417EC7BA.3050604@vmware.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 860 Lines: 22 On Tue, 26 Oct 2004, Zachary Amsden wrote: > > I noticed an unneeded write to dr7 in the signal handling path for x86. > We only need to write to dr7 if there is a breakpoint to re-enable, and > MOVDR is a serializing instruction, which is expensive. Getting rid of > it gets a 33% faster signal delivery path (at least on Xeon - I didn't > test other CPUs, so your gain may vary). I'm suprised it is _that_ slow, but sure, no problem, the patch just makes it match all the other paths. I suspect Xeon is alone in being _that_ slow - I bet Netburst flushes the whole trace cache on db7 writes. Linus - 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/