linux-kernel - Re: [PATCH 2/5] perf: generic intel uncore support

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Message-ID: <4F72F4E0.6010609@intel.com>
Date:	Wed, 28 Mar 2012 19:24:16 +0800
From:	"Yan, Zheng" <zheng.z.yan@...el.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	a.p.zijlstra@...llo.nl, mingo@...e.hu, eranian@...gle.com,
	linux-kernel@...r.kernel.org, ming.m.lin@...el.com
Subject: Re: [PATCH 2/5] perf: generic intel uncore support

On 03/28/2012 05:24 PM, Andi Kleen wrote:
> Overall the driver looks rather good. Thanks.
> 
> On Wed, Mar 28, 2012 at 02:43:15PM +0800, Yan, Zheng wrote:
>> +static void uncore_perf_event_update(struct intel_uncore_box *box,
>> +				      struct perf_event *event)
>> +{
>> +	raw_spin_lock(&box->lock);
> 
> I think a raw lock would be only needed if the uncore was called
> from the scheduler context switch, which it should not be.
> 
> So you can use a normal lock instead of a raw lock.
>
> 
>> +static void uncore_pmu_start_hrtimer(struct intel_uncore_box *box)
>> +{
>> +	__hrtimer_start_range_ns(&box->hrtimer,
>> +				ns_to_ktime(UNCORE_PMU_HRTIMER_INTERVAL), 0,
>> +				HRTIMER_MODE_REL_PINNED, 0);
>> +}
> 
> Can probably do some slack to be more friendly for power.
> 
>> +static struct intel_uncore_box *
>> +uncore_pmu_find_box(struct intel_uncore_pmu *pmu, int phyid)
>> +{
>> +	struct intel_uncore_box *box;
>> +
>> +	rcu_read_lock();
> 
> I'm not sure RCU is really needed here, are any of those paths
> time critical? But ok shouldn't hurt either.
>
It's not time critical. but using RCU here is as simple as
using lock. So I decided to use RCU.

 
>> +static int __init uncore_cpu_init(void)
>> +{
>> +	int ret, cpu;
>> +
>> +	switch (boot_cpu_data.x86_model) {
>> +	default:
>> +		return 0;
>> +	}
> 
> Needs a case? Always returns?

later patches add code to here

> 
>> +
>> +	ret = uncore_types_init(msr_uncores);
>> +	if (ret)
>> +		return ret;
>> +
>> +	get_online_cpus();
>> +	for_each_online_cpu(cpu)
>> +		uncore_cpu_prepare(cpu);
>> +
>> +	preempt_disable();
>> +	smp_call_function(uncore_cpu_setup, NULL, 1);
>> +	uncore_cpu_setup(NULL);
>> +	preempt_enable();
> 
> That's on_each_cpu()
> 
will switch to on_each_cpu() in later version of patches

Thanks
Yan, Zheng
> 
> -Andi

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