linux-kernel - Re: [PATCH 02/10] x86, perf: Support sysfs files depending on SMT status

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Date:	Thu, 12 May 2016 10:05:16 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	acme@...nel.org, peterz@...radead.org, jolsa@...nel.org,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 02/10] x86, perf: Support sysfs files depending on SMT
 status


* Andi Kleen <andi@...stfloor.org> wrote:

> +ssize_t events_ht_sysfs_show(struct device *dev, struct device_attribute *attr,
> +			  char *page)
> +{
> +	struct perf_pmu_events_ht_attr *pmu_attr =
> +		container_of(attr, struct perf_pmu_events_ht_attr, attr);
> +
> +	/*
> +	 * Report conditional events depending on Hyper-Threading.
> +	 *
> +	 * This is overly conservative as usually the HT special
> +	 * handling is not needed if the other CPU thread is idle.
> +	 *
> +	 * Note this does not (cannot) handle the case when thread
> +	 * siblings are invisible, for example with virtualization
> +	 * if they are owned by some other guest.  The user tool
> +	 * has to re-read when a thread sibling gets onlined later.
> +	 */
> +
> +	return sprintf(page, "%s",
> +			topology_max_smt_threads() > 1 ?
> +			pmu_attr->event_str_ht :
> +			pmu_attr->event_str_noht);
> +}
> +
>  EVENT_ATTR(cpu-cycles,			CPU_CYCLES		);
>  EVENT_ATTR(instructions,		INSTRUCTIONS		);
>  EVENT_ATTR(cache-references,		CACHE_REFERENCES	);
> diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
> index 8bd764df815d..ad2e870f77d9 100644
> --- a/arch/x86/events/perf_event.h
> +++ b/arch/x86/events/perf_event.h
> @@ -668,6 +668,14 @@ static struct perf_pmu_events_attr event_attr_##v = {			\
>  	.event_str	= str,						\
>  };
>  
> +#define EVENT_ATTR_STR_HT(_name, v, noht, ht)				\
> +static struct perf_pmu_events_ht_attr event_attr_##v = {		\
> +	.attr		= __ATTR(_name, 0444, events_ht_sysfs_show, NULL),\
> +	.id		= 0,						\
> +	.event_str_noht	= noht,						\
> +	.event_str_ht	= ht,						\
> +}
> +
>  extern struct x86_pmu x86_pmu __read_mostly;
>  
>  static inline bool x86_pmu_has_lbr_callstack(void)
> @@ -938,6 +946,12 @@ int p6_pmu_init(void);
>  
>  int knc_pmu_init(void);
>  
> +ssize_t events_sysfs_show(struct device *dev, struct device_attribute *attr,
> +			  char *page);
> +
> +ssize_t events_ht_sysfs_show(struct device *dev, struct device_attribute *attr,
> +			  char *page);
> +
>  static inline int is_ht_workaround_enabled(void)
>  {
>  	return !!(x86_pmu.flags & PMU_FL_EXCL_ENABLED);
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 9e1c3ada91c4..b425f2d24b26 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -1304,6 +1304,13 @@ struct perf_pmu_events_attr {
>  	const char *event_str;
>  };
>  
> +struct perf_pmu_events_ht_attr {
> +	struct device_attribute attr;
> +	u64 id;
> +	const char *event_str_ht;
> +	const char *event_str_noht;
> +};
> +
>  ssize_t perf_event_sysfs_show(struct device *dev, struct device_attribute *attr,
>  			      char *page);
>  

NAK for the following stylistic reasons:

 - structure definition does not follow existing style.

 - silly line breaks inserted into random positions that make the code ugly.

Thanks,

	Ingo