Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754534Ab0LFUiv (ORCPT ); Mon, 6 Dec 2010 15:38:51 -0500 Received: from smtp-out.google.com ([74.125.121.35]:34196 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754001Ab0LFUiu (ORCPT ); Mon, 6 Dec 2010 15:38:50 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-type:content-transfer-encoding; b=sudrAoDBCzwii4HHM+8TAEvQnIz3i5uNpHNYaCYbCtNKId21y4c+77HkHVSFUQQlLo UQgk1VkoGyYrOslxdNQA== MIME-Version: 1.0 In-Reply-To: <4CF9F7AB.8050802@redhat.com> References: <1291421609-14665-1-git-send-email-dhsharp@google.com> <1291421609-14665-8-git-send-email-dhsharp@google.com> <4CF9F7AB.8050802@redhat.com> From: David Sharp Date: Mon, 6 Dec 2010 12:38:26 -0800 Message-ID: Subject: Re: [PATCH 07/15] ftrace: fix event alignment: kvm:kvm_hv_hypercall To: Avi Kivity Cc: rostedt@goodmis.org, linux-kernel@vger.kernel.org, mrubin@google.com, kvm-devel Content-Type: text/plain; charset=UTF-8 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id oB6Kd2xg018873 Content-Length: 1888 Lines: 45 On Sat, Dec 4, 2010 at 12:11 AM, Avi Kivity wrote: > On 12/04/2010 02:13 AM, David Sharp wrote: >> >> Signed-off-by: David Sharp >> --- >>  arch/x86/kvm/trace.h |    8 ++++---- >>  1 files changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h >> index a6544b8..ab41fb0 100644 >> --- a/arch/x86/kvm/trace.h >> +++ b/arch/x86/kvm/trace.h >> @@ -62,21 +62,21 @@ TRACE_EVENT(kvm_hv_hypercall, >>        TP_ARGS(code, fast, rep_cnt, rep_idx, ingpa, outgpa), >> >>        TP_STRUCT__entry( >> -               __field(        __u16,          code            ) >> -               __field(        bool,           fast            ) >>                __field(        __u16,          rep_cnt         ) >>                __field(        __u16,          rep_idx         ) >>                __field(        __u64,          ingpa           ) >>                __field(        __u64,          outgpa          ) >> +               __field(        __u16,          code            ) >> +               __field(        bool,           fast            ) >>        ), >> > > Looks like a pessimisation. > > Before: 24 bytes > After: 32 bytes > > (on a 64-bit machine, assuming no packing) This patch is predicated on packing the event structures. And since the ring buffer is 32-bit addressable, I don't attempt to improve alignment beyond 32-bit boundaries. > > -- > I have a truly marvellous patch that fixes the bug which this > signature is too narrow to contain. > > ????{.n?+???????+%?????ݶ??w??{.n?+????{??G?????{ay?ʇڙ?,j??f???h?????????z_??(?階?ݢj"???m??????G????????????&???~???iO???z??v?^?m???? ????????I?