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

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Message-ID: <20120328092446.GY22197@one.firstfloor.org>
Date:	Wed, 28 Mar 2012 11:24:46 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	"Yan, Zheng" <zheng.z.yan@...el.com>
Cc:	a.p.zijlstra@...llo.nl, mingo@...e.hu, andi@...stfloor.org,
	eranian@...gle.com, linux-kernel@...r.kernel.org,
	ming.m.lin@...el.com
Subject: Re: [PATCH 2/5] perf: generic intel uncore support

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.

> +static int __init uncore_cpu_init(void)
> +{
> +	int ret, cpu;
> +
> +	switch (boot_cpu_data.x86_model) {
> +	default:
> +		return 0;
> +	}

Needs a case? Always returns?

> +
> +	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()


-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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