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Date: Mon, 02 Jul 2012 16:19:06 -0400
From: William Cohen <wcohen@...hat.com>
To: Robert Richter <robert.richter@....com>
CC: Will Deacon <will.deacon@....com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Matt Fleming <matt@...sole-pimps.org>
Subject: Re: [PATCH] oprofile, perf: Use per-cpu framework
On 06/22/2012 10:42 AM, Robert Richter wrote:
> Will,
>
> On 15.06.12 17:19:54, Will Deacon wrote:
>> On Fri, Jun 15, 2012 at 05:16:35PM +0100, Robert Richter wrote:
>>> On 15.06.12 16:43:59, Will Deacon wrote:
>>>> Given both the lack of feedback and the trivial nature of this patch would
>>>> you be able to pick this up please? I'd rather not push it via the ARM tree
>>>> as the change is under drivers/.
>>>
>>> Will, I will apply it. Sorry for not responding earlier.
>
> I just realized I wrote a patch some time ago that introduces per_cpu
> variables, see below. Please give it a try to, I will then queue it
> for v3.6.
>
> Your patch should go upstream anyway to make it into stable trees.
>
> Thanks,
>
> -Robert
Hi Robert,
I was able to build a linux-3.5.0-rc5+ kernel with this patch and the following troublesome config entry enabled:
CONFIG_DEBUG_PER_CPU_MAPS=y
The resulting kernel ran and oprofile functioned fine on a compulab trimslice machine.
-Will
>
>
> From f8bbfd7d28303967ca4e8597de9bdc9bf8b197e7 Mon Sep 17 00:00:00 2001
> From: Robert Richter <robert.richter@....com>
> Date: Thu, 23 Feb 2012 17:07:06 +0100
> Subject: [PATCH] oprofile, perf: Use per-cpu framework
>
> This changes oprofile_perf.c to use the per-cpu framework.
>
> Using the per-cpu framework should avoid error like the following:
>
> arch/arm/oprofile/../../../drivers/oprofile/oprofile_perf.c:28:28: error: variably modified 'perf_events' at file scope
>
> Reported-by: William Cohen <wcohen@...hat.com>
> Cc: Will Deacon <will.deacon@....com>
> Signed-off-by: Robert Richter <robert.richter@....com>
> ---
> drivers/oprofile/oprofile_perf.c | 23 +++++++++++------------
> 1 files changed, 11 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/oprofile/oprofile_perf.c b/drivers/oprofile/oprofile_perf.c
> index efc4b7f..f3cfa0b 100644
> --- a/drivers/oprofile/oprofile_perf.c
> +++ b/drivers/oprofile/oprofile_perf.c
> @@ -1,5 +1,6 @@
> /*
> * Copyright 2010 ARM Ltd.
> + * Copyright 2012 Advanced Micro Devices, Inc., Robert Richter
> *
> * Perf-events backend for OProfile.
> */
> @@ -25,7 +26,7 @@ static int oprofile_perf_enabled;
> static DEFINE_MUTEX(oprofile_perf_mutex);
>
> static struct op_counter_config *counter_config;
> -static struct perf_event **perf_events[NR_CPUS];
> +static DEFINE_PER_CPU(struct perf_event **, perf_events);
> static int num_counters;
>
> /*
> @@ -38,7 +39,7 @@ static void op_overflow_handler(struct perf_event *event,
> u32 cpu = smp_processor_id();
>
> for (id = 0; id < num_counters; ++id)
> - if (perf_events[cpu][id] == event)
> + if (per_cpu(perf_events, cpu)[id] == event)
> break;
>
> if (id != num_counters)
> @@ -74,7 +75,7 @@ static int op_create_counter(int cpu, int event)
> {
> struct perf_event *pevent;
>
> - if (!counter_config[event].enabled || perf_events[cpu][event])
> + if (!counter_config[event].enabled || per_cpu(perf_events, cpu)[event])
> return 0;
>
> pevent = perf_event_create_kernel_counter(&counter_config[event].attr,
> @@ -91,18 +92,18 @@ static int op_create_counter(int cpu, int event)
> return -EBUSY;
> }
>
> - perf_events[cpu][event] = pevent;
> + per_cpu(perf_events, cpu)[event] = pevent;
>
> return 0;
> }
>
> static void op_destroy_counter(int cpu, int event)
> {
> - struct perf_event *pevent = perf_events[cpu][event];
> + struct perf_event *pevent = per_cpu(perf_events, cpu)[event];
>
> if (pevent) {
> perf_event_release_kernel(pevent);
> - perf_events[cpu][event] = NULL;
> + per_cpu(perf_events, cpu)[event] = NULL;
> }
> }
>
> @@ -257,12 +258,12 @@ void oprofile_perf_exit(void)
>
> for_each_possible_cpu(cpu) {
> for (id = 0; id < num_counters; ++id) {
> - event = perf_events[cpu][id];
> + event = per_cpu(perf_events, cpu)[id];
> if (event)
> perf_event_release_kernel(event);
> }
>
> - kfree(perf_events[cpu]);
> + kfree(per_cpu(perf_events, cpu));
> }
>
> kfree(counter_config);
> @@ -277,8 +278,6 @@ int __init oprofile_perf_init(struct oprofile_operations *ops)
> if (ret)
> return ret;
>
> - memset(&perf_events, 0, sizeof(perf_events));
> -
> num_counters = perf_num_counters();
> if (num_counters <= 0) {
> pr_info("oprofile: no performance counters\n");
> @@ -298,9 +297,9 @@ int __init oprofile_perf_init(struct oprofile_operations *ops)
> }
>
> for_each_possible_cpu(cpu) {
> - perf_events[cpu] = kcalloc(num_counters,
> + per_cpu(perf_events, cpu) = kcalloc(num_counters,
> sizeof(struct perf_event *), GFP_KERNEL);
> - if (!perf_events[cpu]) {
> + if (!per_cpu(perf_events, cpu)) {
> pr_info("oprofile: failed to allocate %d perf events "
> "for cpu %d\n", num_counters, cpu);
> ret = -ENOMEM;
--
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