Re: [rfc] perf p4 events aliases

[Don Zickus <dzickus@redhat.com>]

On Thu, Jul 07, 2011 at 07:28:49PM +0400, Cyrill Gorcunov wrote:
> Hi Don, if you have a chance could you please check if this
> patch does a trick for nmi-watchdog and perf top? The idea
> is to use aliases as being proposed early.

Hmm, didn't work for me.  The watchdog seems to work but 'perf top' showed
nothing (even after 30 seconds).  I tried this on Linus's latest -tip and
Ingo's perf/core -tip.  No luck.

Cheers,
Don

> 
> Note I commented out hw_watchdog_set_attr method to be sure
> this hook doesn't take place so you get "defined but not used"
> warning but it's known to happen.
> 
> Some details -- I think alias should be allowed for general
> events only so any raw event will never fit aliasing feature.
> 
> Compile tested only, so I guess most probably something will
> goes wrong or fail, but anyway ;) Thanks!
> 
> Patch is on top of current -tip/perf/core
> 
>  | commit 931da6137e8e8c622f59251e8b645467aea293f1
> 
> 	Cyrill
> ---
>  arch/x86/include/asm/perf_event_p4.h |    6 ++
>  arch/x86/kernel/cpu/perf_event_p4.c  |   80 +++++++++++++++++++++++++++++++++--
>  2 files changed, 82 insertions(+), 4 deletions(-)
> 
> Index: linux-2.6.git/arch/x86/include/asm/perf_event_p4.h
> ===================================================================
> --- linux-2.6.git.orig/arch/x86/include/asm/perf_event_p4.h
> +++ linux-2.6.git/arch/x86/include/asm/perf_event_p4.h
> @@ -757,6 +757,12 @@ enum P4_ESCR_EMASKS {
>  #define P4_PEBS_CONFIG_MASK		0xff
>  
>  /*
> + * If event may have alias it should be marked
> + * with special bit.
> + */
> +#define P4_CONFIG_ALIASABLE		(1 << 9)
> +
> +/*
>   * mem: Only counters MSR_IQ_COUNTER4 (16) and
>   * MSR_IQ_COUNTER5 (17) are allowed for PEBS sampling
>   */
> Index: linux-2.6.git/arch/x86/kernel/cpu/perf_event_p4.c
> ===================================================================
> --- linux-2.6.git.orig/arch/x86/kernel/cpu/perf_event_p4.c
> +++ linux-2.6.git/arch/x86/kernel/cpu/perf_event_p4.c
> @@ -570,11 +570,72 @@ static __initconst const u64 p4_hw_cache
>   },
>  };
>  
> +/*
> + * Because of Netburst being quite restricted in now
> + * many similar events can run simultaneously we use
> + * that named event aliases, ie different events which
> + * have the same functionallity but use non-intersected
> + * ESCR/CCCR/couter registers which relax restrictions a
> + * bit and run two or more semi-same events together.
> + * This is done transparently to a user space.
> + *
> + * Never set P4_CONFIG_HT bit here nor the P4_PEBS_METRIC,
> + * they either up-to-dated automatically either not appliable
> + * at all, so be really carefull choosing aliases.
> + *
> + */
> +struct p4_event_alias {
> +	u64 orig;
> +	u64 alter;
> +} p4_event_aliases[] = {
> +  {
> +	.orig	=
> +		p4_config_pack_escr(P4_ESCR_EVENT(P4_EVENT_GLOBAL_POWER_EVENTS)		|
> +				    P4_ESCR_EMASK_BIT(P4_EVENT_GLOBAL_POWER_EVENTS, RUNNING)),
> +	.alter	=
> +		p4_config_pack_escr(P4_ESCR_EVENT(P4_EVENT_EXECUTION_EVENT)		|
> +				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, NBOGUS0)|
> +				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, NBOGUS1)|
> +				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, NBOGUS2)|
> +				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, NBOGUS3)|
> +				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, BOGUS0)	|
> +				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, BOGUS1)	|
> +				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, BOGUS2)	|
> +				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, BOGUS3))|
> +		p4_config_pack_cccr(P4_CCCR_THRESHOLD(15) | P4_CCCR_COMPLEMENT		|
> +				    P4_CCCR_COMPARE),
> +  },
> +};
> +
> +static u64 p4_get_alias_event(u64 config)
> +{
> +	int i;
> +
> +	if (!(config & P4_CONFIG_ALIASABLE))
> +		return 0;
> +
> +	config &= P4_CONFIG_MASK;
> +
> +	/*
> +	 * If an event was previously already swapped to
> +	 * alter config we can swap it back when needed.
> +	 */
> +	for (i = 0; i < ARRAY_SIZE(p4_event_aliases); i++) {
> +		if (config == p4_event_aliases[i].orig)
> +			return p4_event_aliases[i].alter | P4_CONFIG_ALIASABLE;
> +		else if (config == p4_event_aliases[i].alter)
> +			return p4_event_aliases[i].orig | P4_CONFIG_ALIASABLE;
> +	}
> +
> +	return 0;
> +}
> +
>  static u64 p4_general_events[PERF_COUNT_HW_MAX] = {
>    /* non-halted CPU clocks */
>    [PERF_COUNT_HW_CPU_CYCLES] =
>  	p4_config_pack_escr(P4_ESCR_EVENT(P4_EVENT_GLOBAL_POWER_EVENTS)		|
> -		P4_ESCR_EMASK_BIT(P4_EVENT_GLOBAL_POWER_EVENTS, RUNNING)),
> +		P4_ESCR_EMASK_BIT(P4_EVENT_GLOBAL_POWER_EVENTS, RUNNING))	|
> +		P4_CONFIG_ALIASABLE,
>  
>    /*
>     * retired instructions
> @@ -1159,6 +1220,7 @@ static int p4_pmu_schedule_events(struct
>  	struct p4_event_bind *bind;
>  	unsigned int i, thread, num;
>  	int cntr_idx, escr_idx;
> +	u64 config_alias;
>  
>  	bitmap_zero(used_mask, X86_PMC_IDX_MAX);
>  	bitmap_zero(escr_mask, P4_ESCR_MSR_TABLE_SIZE);
> @@ -1167,6 +1229,7 @@ static int p4_pmu_schedule_events(struct
>  
>  		hwc = &cpuc->event_list[i]->hw;
>  		thread = p4_ht_thread(cpu);
> +again:
>  		bind = p4_config_get_bind(hwc->config);
>  		escr_idx = p4_get_escr_idx(bind->escr_msr[thread]);
>  		if (unlikely(escr_idx == -1))
> @@ -1180,8 +1243,17 @@ static int p4_pmu_schedule_events(struct
>  		}
>  
>  		cntr_idx = p4_next_cntr(thread, used_mask, bind);
> -		if (cntr_idx == -1 || test_bit(escr_idx, escr_mask))
> -			goto done;
> +		if (cntr_idx == -1 || test_bit(escr_idx, escr_mask)) {
> +			/*
> +			 * Probably an event alias is still available.
> +			 */
> +			config_alias = p4_get_alias_event(hwc->config);
> +			if (!config_alias)
> +				goto done;
> +			/* Don't forget to restore HT */
> +			hwc->config = thread ? p4_set_ht_bit(config_alias) : config_alias;
> +			goto again;
> +		}
>  
>  		p4_pmu_swap_config_ts(hwc, cpu);
>  		if (assign)
> @@ -1218,7 +1290,7 @@ static __initconst const struct x86_pmu 
>  	.cntval_bits		= ARCH_P4_CNTRVAL_BITS,
>  	.cntval_mask		= ARCH_P4_CNTRVAL_MASK,
>  	.max_period		= (1ULL << (ARCH_P4_CNTRVAL_BITS - 1)) - 1,
> -	.hw_watchdog_set_attr	= p4_hw_watchdog_set_attr,
> +	/* .hw_watchdog_set_attr	= p4_hw_watchdog_set_attr, */
>  	.hw_config		= p4_hw_config,
>  	.schedule_events	= p4_pmu_schedule_events,
>  	/*
> --
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