Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753417Ab1FHJg7 (ORCPT ); Wed, 8 Jun 2011 05:36:59 -0400 Received: from r00tworld.com ([212.85.137.150]:38553 "EHLO r00tworld.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752955Ab1FHJg6 (ORCPT ); Wed, 8 Jun 2011 05:36:58 -0400 From: pageexec@freemail.hu To: Andi Kleen Date: Wed, 08 Jun 2011 11:35:11 +0200 MIME-Version: 1.0 Subject: Re: [PATCH v5 8/9] x86-64: Emulate legacy vsyscalls Reply-to: pageexec@freemail.hu CC: Ingo Molnar , Andrew Lutomirski , x86@kernel.org, Thomas Gleixner , linux-kernel@vger.kernel.org, Jesper Juhl , Borislav Petkov , Linus Torvalds , Andrew Morton , Arjan van de Ven , Jan Beulich , richard -rw- weinberger , Mikael Pettersson , Andi Kleen , Brian Gerst , Louis Rilling , Valdis.Kletnieks@vt.edu Message-ID: <4DEF424F.2351.1C15AD40@pageexec.freemail.hu> In-reply-to: <20110608091120.GI27166@one.firstfloor.org> References: <20110608064857.GA6747@elte.hu>, <4DEF3A93.8871.1BF773E2@pageexec.freemail.hu>, <20110608091120.GI27166@one.firstfloor.org> X-mailer: Pegasus Mail for Windows (4.61) Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT Content-description: Mail message body X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-2.1.12 (r00tworld.com [212.85.137.150]); Wed, 08 Jun 2011 11:35:49 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 880 Lines: 18 On 8 Jun 2011 at 11:11, Andi Kleen wrote: > There's clear evidence that any kind of exception in gettimeofday()/time() > is too slow. A few years ago gtod() had CPUID which lead to intercepts > with many hypervisors. This turned out to be a unacceptable slowdown, > so it was fixed, yes, i don't think anyone claimed any performance improvements from moving away from the vsyscall page into taking exceptions ;). i think everyone considers this as a stop-gap compatibility measure only that will be less and less relevant and eventually may even go away as time progresses and linux systems begin to fully rely on the vdso instead. -- 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/