From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751798AbaBBQCM (ORCPT ); Sun, 2 Feb 2014 11:02:12 -0500 Received: from www84.your-server.de ([213.133.104.84]:48325 "EHLO www84.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751637AbaBBQCK (ORCPT ); Sun, 2 Feb 2014 11:02:10 -0500 Message-ID: <1391356972.1158.4.camel@wall-e.seibold.net> Subject: Re: [PATCH 6/8] cleanup __vdso_gettimeofday From: Stefani Seibold To: "H. Peter Anvin" Cc: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, ak@linux.intel.com, aarcange@redhat.com, john.stultz@linaro.org, luto@amacapital.net, xemul@parallels.com, gorcunov@openvz.org, andriy.shevchenko@linux.intel.com, Martin.Runge@rohde-schwarz.com, Andreas.Brief@rohde-schwarz.com Date: Sun, 02 Feb 2014 17:02:52 +0100 In-Reply-To: References: <1391340435-5130-1-git-send-email-stefani@seibold.net> <1391340435-5130-7-git-send-email-stefani@seibold.net> Content-Type: text/plain; charset="us-ascii" X-Mailer: Evolution 3.8.5 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Authenticated-Sender: stefani@seibold.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2014-02-02 at 07:43 -0800, H. Peter Anvin wrote: > Even reading the timezone via gettimeofday is the uncommon case... never mind only the timezome. Whatever you do please don't slow down the common case. > > On February 2, 2014 3:27:13 AM PST, stefani@seibold.net wrote: > >From: Stefani Seibold > > > >This patch do a little cleanup for the __vdso_gettimeofday() function. > > > >It kick out an unneeded ret local variable and makes the code faster if > >only the timezone is needed. > > > >Signed-off-by: Stefani Seibold > >--- > > arch/x86/vdso/vclock_gettime.c | 7 ++----- > > 1 file changed, 2 insertions(+), 5 deletions(-) > > > >diff --git a/arch/x86/vdso/vclock_gettime.c > >b/arch/x86/vdso/vclock_gettime.c > >index 743f277..bf969a0 100644 > >--- a/arch/x86/vdso/vclock_gettime.c > >+++ b/arch/x86/vdso/vclock_gettime.c > >@@ -259,13 +259,12 @@ int clock_gettime(clockid_t, struct timespec *) > > > >notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone > >*tz) > > { > >- long ret = VCLOCK_NONE; > >- > > if (likely(tv != NULL)) { > > BUILD_BUG_ON(offsetof(struct timeval, tv_usec) != > > offsetof(struct timespec, tv_nsec) || > > sizeof(*tv) != sizeof(struct timespec)); > >- ret = do_realtime((struct timespec *)tv); > >+ if (do_realtime((struct timespec *)tv) == VCLOCK_NONE) > >+ return vdso_fallback_gtod(tv, tz); > > tv->tv_usec /= 1000; > > } > > if (unlikely(tz != NULL)) { > >@@ -274,8 +273,6 @@ notrace int __vdso_gettimeofday(struct timeval *tv, > >struct timezone *tz) > > tz->tz_dsttime = gtod->sys_tz.tz_dsttime; > > } > > > >- if (ret == VCLOCK_NONE) > >- return vdso_fallback_gtod(tv, tz); > > return 0; > > } > > int gettimeofday(struct timeval *, struct timezone *) > I don't see where i slow down the common case! It is exactly the same behaviour as the original code. Only in the uncommon case where the tv == NULL and tz != NULL is a bit faster.