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Message-ID: <1347032350.18408.88.camel@twins>
Subject: Re: [PATCH 1/3] perf: use hrtimer for event multiplexing
From: Peter Zijlstra <peterz@infradead.org>
To: Stephane Eranian <eranian@google.com>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, ak@linux.intel.com,
        zheng.z.yan@intel.com, robert.richter@amd.com
Date: Fri, 07 Sep 2012 17:39:10 +0200
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On Fri, 2012-09-07 at 16:29 +0200, Stephane Eranian wrote:
> @@ -148,6 +148,15 @@ static LIST_HEAD(pmus);
>  static DEFINE_MUTEX(pmus_lock);
>  static struct srcu_struct pmus_srcu;
>  
> +struct perf_cpu_hrtimer {
> +       struct hrtimer hrtimer;
> +       int active;
> +};
> +
> +static DEFINE_PER_CPU(struct list_head, rotation_list);
> +
> +static DEFINE_PER_CPU(struct perf_cpu_hrtimer, perf_cpu_hrtimer);


How about sticking the hrtimer in perf_cpu_context so you can have a
different rotation interval per PMU ?

Sorta like e9d2b064149ff7ef4acbc65a1b9374ac8b218d3e removed. Stopping
the timer when the PMU isn't over committed should solve the NOHZ
problem I think.