From: Frederic Weisbecker <fweisbec@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Paul Mackerras <paulus@samba.org>,
David Miller <davem@davemloft.net>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 1/2] perf: Correctly align perf event tracing buffer
Date: Mon, 29 Mar 2010 19:51:26 +0200 [thread overview]
Message-ID: <20100329175124.GC5101@nowhere> (raw)
In-Reply-To: <1269883209.12097.366.camel@laptop>
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.
next prev parent reply other threads:[~2010-03-29 17:51 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-28 5:11 [GIT PULL] perf fixes Frederic Weisbecker
2010-03-28 5:11 ` [PATCH 1/2] perf: Correctly align perf event tracing buffer Frederic Weisbecker
2010-03-29 8:51 ` Peter Zijlstra
2010-03-29 17:16 ` Frederic Weisbecker
2010-03-29 17:20 ` Peter Zijlstra
2010-03-29 17:51 ` Frederic Weisbecker [this message]
2010-03-28 5:11 ` [PATCH 2/2] perf: Use hot regs with software sched switch/migrate events Frederic Weisbecker
2010-03-29 8:49 ` Peter Zijlstra
2010-03-29 17:47 ` Frederic Weisbecker
2010-03-29 18:05 ` Peter Zijlstra
2010-03-29 22:43 ` Frederic Weisbecker
2010-03-29 22:53 ` Frederic Weisbecker
2010-03-30 18:54 ` Peter Zijlstra
2010-03-30 19:14 ` Frederic Weisbecker
2010-03-29 3:33 ` [GIT PULL] perf fixes Ingo Molnar
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