From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755294Ab0C2Rvb (ORCPT ); Mon, 29 Mar 2010 13:51:31 -0400 Received: from mail-gx0-f217.google.com ([209.85.217.217]:39538 "EHLO mail-gx0-f217.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754832Ab0C2Rva (ORCPT ); Mon, 29 Mar 2010 13:51:30 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=XlHHKSB9QuMHdl9SnPB2EIPJgRIw9uIFDobanKHXMvjbG75F4ZvlRsOvWb2xxN7A9i ffBs6DmyxjfQUK0jZyHns8uFB13Jce+DINpQseeD8+vxrUlS1APUA3CRfNp5nBYKJDgC NMJsm9k39d7jb55TaYbeByZpsOkn2ZlIYXSQ0= Date: Mon, 29 Mar 2010 19:51:26 +0200 From: Frederic Weisbecker To: Peter Zijlstra Cc: Ingo Molnar , LKML , Arnaldo Carvalho de Melo , Paul Mackerras , David Miller , Steven Rostedt Subject: Re: [PATCH 1/2] perf: Correctly align perf event tracing buffer Message-ID: <20100329175124.GC5101@nowhere> References: <1269753066-17246-1-git-send-regression-fweisbec@gmail.com> <1269753066-17246-2-git-send-regression-fweisbec@gmail.com> <1269852691.12097.162.camel@laptop> <20100329171615.GA5101@nowhere> <1269883209.12097.366.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1269883209.12097.366.camel@laptop> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 29, 2010 at 07:20:09PM +0200, Peter Zijlstra wrote: > On Mon, 2010-03-29 at 19:16 +0200, Frederic Weisbecker wrote: > > On Mon, Mar 29, 2010 at 10:51:31AM +0200, Peter Zijlstra wrote: > > > On Sun, 2010-03-28 at 07:11 +0200, Frederic Weisbecker wrote: > > > > kernel/trace/trace_event_perf.c | 11 +++++++++-- > > > > 1 files changed, 9 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c > > > > index 0709e4f..69941f3 100644 > > > > --- a/kernel/trace/trace_event_perf.c > > > > +++ b/kernel/trace/trace_event_perf.c > > > > @@ -15,7 +15,12 @@ EXPORT_PER_CPU_SYMBOL_GPL(perf_trace_regs); > > > > static char *perf_trace_buf; > > > > static char *perf_trace_buf_nmi; > > > > > > > > -typedef typeof(char [PERF_MAX_TRACE_SIZE]) perf_trace_t ; > > > > +/* > > > > + * Force it to be aligned to unsigned long to avoid misaligned accesses > > > > + * suprises > > > > + */ > > > > +typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)]) > > > > + perf_trace_t; > > > > > > > > > > wouldn't __aligned(8) be simpler? > > > > > > David and Tejun seemed to prefer to create the alignment on the > > type level rather than using an align. > > > > I'm personally fine either way. > > Also, if you need u64 alignment, shouldn't you use u64 instead of > unsigned long, the alignment requirement on those two might differ on > 32bit machines. Yeah but we need the u64 alignment only on 64 bits machines.