linux-kernel - Re: [PATCH v1 09/10] perf/x86/uncore: add hrtimer to SNB uncore IMC PMU

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Date:	Mon, 10 Feb 2014 14:04:48 +0800
From:	"Yan, Zheng" <zheng.z.yan@...el.com>
To:	Stephane Eranian <eranian@...gle.com>, linux-kernel@...r.kernel.org
CC:	peterz@...radead.org, mingo@...e.hu, acme@...hat.com,
	ak@...ux.intel.com
Subject: Re: [PATCH v1 09/10] perf/x86/uncore: add hrtimer to SNB uncore IMC
 PMU

On 02/03/2014 08:55 PM, Stephane Eranian wrote:
> This patch is needed because that PMU uses 32-bit free
> running counters with no interrupt capabilities.
> 
> On SNB/IVB/HSW, we used 20GB/s theoretical peak to calculate
> the hrtimer timeout necessary to avoid missing an overflow.
> That delay is set to 5s to be on the cautious side.
> 
> The SNB IMC uses free running counters, which are handled
> via pseudo fixed counters. The SNB IMC PMU implementation
> supports an arbitrary number of events, because the counters
> are read-only. Therefore it is not possible to track active
> counters. Instead we put active events on a linked list which
> is then used by the hrtimer handler to update the SW counts.
> 
> Signed-off-by: Stephane Eranian <eranian@...gle.com>
> ---
>  arch/x86/kernel/cpu/perf_event_intel_uncore.c |   12 ++++++++++++
>  arch/x86/kernel/cpu/perf_event_intel_uncore.h |    2 ++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
> index 8b1f81f..f76937e 100644
> --- a/arch/x86/kernel/cpu/perf_event_intel_uncore.c
> +++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
> @@ -1730,6 +1730,7 @@ static void snb_uncore_imc_init_box(struct intel_uncore_box *box)
>  	addr &= ~(PAGE_SIZE - 1);
>  
>  	box->io_addr = ioremap(addr, SNB_UNCORE_PCI_IMC_MAP_SIZE);
> +	box->hrtimer_duration = UNCORE_SNB_IMC_HRTIMER_INTERVAL;
>  }
>  
>  static void snb_uncore_imc_enable_box(struct intel_uncore_box *box)
> @@ -3166,6 +3167,7 @@ static void uncore_perf_event_update(struct intel_uncore_box *box, struct perf_e
>  static enum hrtimer_restart uncore_pmu_hrtimer(struct hrtimer *hrtimer)
>  {
>  	struct intel_uncore_box *box;
> +	struct perf_event *event;
>  	unsigned long flags;
>  	int bit;
>  
> @@ -3178,6 +3180,14 @@ static enum hrtimer_restart uncore_pmu_hrtimer(struct hrtimer *hrtimer)
>  	 */
>  	local_irq_save(flags);
>  
> +	/*
> +	 * handle boxes with an active event list as opposed to active
> +	 * counters
> +	 */
> +	list_for_each_entry(event, &box->active_list, active_entry) {
> +		uncore_perf_event_update(box, event);
> +	}
> +
>  	for_each_set_bit(bit, box->active_mask, UNCORE_PMC_IDX_MAX)
>  		uncore_perf_event_update(box, box->events[bit]);
>  
> @@ -3227,6 +3237,8 @@ static struct intel_uncore_box *uncore_alloc_box(struct intel_uncore_type *type,
>  	/* set default hrtimer timeout */
>  	box->hrtimer_duration = UNCORE_PMU_HRTIMER_INTERVAL;
>  
> +	INIT_LIST_HEAD(&box->active_list);
> +
>  	return box;
>  }
>  
> diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.h b/arch/x86/kernel/cpu/perf_event_intel_uncore.h
> index 0770da2..634de93 100644
> --- a/arch/x86/kernel/cpu/perf_event_intel_uncore.h
> +++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.h
> @@ -6,6 +6,7 @@
>  
>  #define UNCORE_PMU_NAME_LEN		32
>  #define UNCORE_PMU_HRTIMER_INTERVAL	(60LL * NSEC_PER_SEC)
> +#define UNCORE_SNB_IMC_HRTIMER_INTERVAL (5ULL * NSEC_PER_SEC)
>  
>  #define UNCORE_FIXED_EVENT		0xff
>  #define UNCORE_PMC_IDX_MAX_GENERIC	8
> @@ -492,6 +493,7 @@ struct intel_uncore_box {
>  	u64 hrtimer_duration; /* hrtimer timeout for this box */
>  	struct hrtimer hrtimer;
>  	struct list_head list;
> +	struct list_head active_list;

I think patch 8 and patch 9 are disordered

Regards
Yan, Zheng

>  	void *io_addr;
>  	struct intel_uncore_extra_reg shared_regs[0];
>  };
> 

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