From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH kvm-unit-tests] pmu: fixes for Sandy Bridge hosts Date: Mon, 03 Jun 2013 08:33:13 +0200 Message-ID: <51AC38A9.5010703@redhat.com> References: <1369935788-19069-1-git-send-email-pbonzini@redhat.com> <20130602153209.GJ24773@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Gleb Natapov Return-path: Received: from mail-wg0-f45.google.com ([74.125.82.45]:62591 "EHLO mail-wg0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750861Ab3FCGdZ (ORCPT ); Mon, 3 Jun 2013 02:33:25 -0400 Received: by mail-wg0-f45.google.com with SMTP id n12so2861325wgh.12 for ; Sun, 02 Jun 2013 23:33:24 -0700 (PDT) In-Reply-To: <20130602153209.GJ24773@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Il 02/06/2013 17:32, Gleb Natapov ha scritto: > On Thu, May 30, 2013 at 07:43:07PM +0200, Paolo Bonzini wrote: >> This patch includes two fixes for SB: >> >> * the 3rd fixed counter ("ref cpu cycles") can sometimes report >> less than the number of iterations >> > Is it documented? It is strange for "architectural" counter to behave > differently on different architectures. It just counts the CPU cycles. If the CPU can optimize the loop better, it will take less CPU cycles to execute it. Paolo