linux-kernel - Re: [RFC -tip] perf, x86: Add PERF_COUNT_HW_NMI

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Date:	Tue, 21 Jun 2011 11:23:02 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Cyrill Gorcunov <gorcunov@...nvz.org>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, Lin Ming <ming.m.lin@...el.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Stephane Eranian <eranian@...gle.com>,
	Vince Weaver <vweaver1@...s.utk.edu>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [RFC -tip] perf, x86: Add PERF_COUNT_HW_NMI_WATCHDOG event v2

On Thu, Apr 28, 2011 at 07:37:25PM +0400, Cyrill Gorcunov wrote:
> Due to restriction and specifics of Netburst PMU we need a separated
> event for NMI watchdog. In particular every Netburst event consume not
> just a counter and config register, but also an additional ESCR register.
> Since ESCR registers are grouped upon counters (i.e. if ESCR is occupied
> for some event there is no room for another event to enter the room until
> it's released) we need to pick up "least" used ESCR (or most available)
> for nmi-watchdog purpose -- MSR_P4_CRU_ESCR2/3 was chosen.
> 
> Note that on all other PMUs which support relocation of events between
> counters this event is a simple alias for PERF_COUNT_HW_CPU_CYCLES.

Cyril,

What ever happened with this patch?

Cheers,
Don

> 
> v2: Add a comment about non-sleeping clockticks.
> 
> N.B: An attempts to make an alternate encodings for events didn't make
> situation better because we would need to track how exactly we substitute
> the particular event -- hw::config knows nothing from where the event came,
> from user-space as a raw event or as pre-configured general event. If it
> comes as raw event we have to track every single bit of ESCR mask and find
> out if new event would count exactly the same thing as the former event
> was supposed to. So I found such way inconvenient for users and adding a
> single code snippet seems to be a way more clean approach.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov@...nvz.org>
> Acked-by: Don Zickus <dzickus@...hat.com>
> CC: Ingo Molnar <mingo@...hat.com>
> CC: Lin Ming <ming.m.lin@...el.com>
> CC: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> CC: Arnaldo Carvalho de Melo <acme@...hat.com>
> CC: Frederic Weisbecker <fweisbec@...il.com>
> ---
> 
> To PeterZ: Peter, I've tried various ways to implement an alternate encoding
> (Don even tried one which didn't work because of ESCR conflict ;) but all them
> introduced much code which makes the whole picture more complex I think and
> there is no 1:1 map between even single event (initially I thought we have
> something but eventually found they are not). So even new NMI-WATCHDOG event
> is *not* the same as "power events" were before but they are not supposed to
> be "exactly" precise in compare with cpu-clocks we use for perf top. So I think
> it's acceptable trade off -- less precise events for nmi-watchdog and more
> precise for perf top and friends.
> 
> Don, I put your Ack here because the only thing I've changed (in compare with
> previous tested verion) is PERF_COUNT_HW_NMI_WATCHDOG = 8 (was 7 before), please
> re-test it again, I've tested it already but still.
> 
> Comments are welcome as usuall ;)
> 
>  arch/x86/kernel/cpu/perf_event_amd.c   |    1 +
>  arch/x86/kernel/cpu/perf_event_intel.c |    1 +
>  arch/x86/kernel/cpu/perf_event_p4.c    |   18 ++++++++++++++++++
>  arch/x86/kernel/cpu/perf_event_p6.c    |    1 +
>  include/linux/perf_event.h             |    1 +
>  kernel/watchdog.c                      |    2 +-
>  6 files changed, 23 insertions(+), 1 deletion(-)
> 
> Index: linux-2.6.git/arch/x86/kernel/cpu/perf_event_amd.c
> =====================================================================
> --- linux-2.6.git.orig/arch/x86/kernel/cpu/perf_event_amd.c
> +++ linux-2.6.git/arch/x86/kernel/cpu/perf_event_amd.c
> @@ -102,6 +102,7 @@ static const u64 amd_perfmon_event_map[]
>    [PERF_COUNT_HW_CACHE_MISSES]		= 0x0081,
>    [PERF_COUNT_HW_BRANCH_INSTRUCTIONS]	= 0x00c2,
>    [PERF_COUNT_HW_BRANCH_MISSES]		= 0x00c3,
> +  [PERF_COUNT_HW_NMI_WATCHDOG]		= 0x0076,
>  };
> 
>  static u64 amd_pmu_event_map(int hw_event)
> Index: linux-2.6.git/arch/x86/kernel/cpu/perf_event_intel.c
> =====================================================================
> --- linux-2.6.git.orig/arch/x86/kernel/cpu/perf_event_intel.c
> +++ linux-2.6.git/arch/x86/kernel/cpu/perf_event_intel.c
> @@ -34,6 +34,7 @@ static u64 intel_perfmon_event_map[PERF_
>    [PERF_COUNT_HW_BRANCH_INSTRUCTIONS]	= 0x00c4,
>    [PERF_COUNT_HW_BRANCH_MISSES]		= 0x00c5,
>    [PERF_COUNT_HW_BUS_CYCLES]		= 0x013c,
> +  [PERF_COUNT_HW_NMI_WATCHDOG]		= 0x003c,
>  };
> 
>  static struct event_constraint intel_core_event_constraints[] __read_mostly =
> 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
> @@ -607,6 +607,24 @@ static u64 p4_general_events[PERF_COUNT_
>  		P4_ESCR_EMASK_BIT(P4_EVENT_FSB_DATA_ACTIVITY, DRDY_DRV)		|
>  		P4_ESCR_EMASK_BIT(P4_EVENT_FSB_DATA_ACTIVITY, DRDY_OWN))	|
>  	p4_config_pack_cccr(P4_CCCR_EDGE | P4_CCCR_COMPARE),
> +
> +  /*
> +   * This is a specific way to count non-halted clockticks as SDM Vol.3B
> +   * "30.11.2 Non-Sleep Clockticks" suggest. We set threshold and complement
> +   * flag as result every tick is accounted and delivered to the counter.
> +   */
> +  [PERF_COUNT_HW_NMI_WATCHDOG] =
> +	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 struct p4_event_bind *p4_config_get_bind(u64 config)
> Index: linux-2.6.git/arch/x86/kernel/cpu/perf_event_p6.c
> =====================================================================
> --- linux-2.6.git.orig/arch/x86/kernel/cpu/perf_event_p6.c
> +++ linux-2.6.git/arch/x86/kernel/cpu/perf_event_p6.c
> @@ -12,6 +12,7 @@ static const u64 p6_perfmon_event_map[]
>    [PERF_COUNT_HW_BRANCH_INSTRUCTIONS]	= 0x00c4,
>    [PERF_COUNT_HW_BRANCH_MISSES]		= 0x00c5,
>    [PERF_COUNT_HW_BUS_CYCLES]		= 0x0062,
> +  [PERF_COUNT_HW_NMI_WATCHDOG]		= 0x0079,
>  };
> 
>  static u64 p6_pmu_event_map(int hw_event)
> Index: linux-2.6.git/include/linux/perf_event.h
> =====================================================================
> --- linux-2.6.git.orig/include/linux/perf_event.h
> +++ linux-2.6.git/include/linux/perf_event.h
> @@ -53,6 +53,7 @@ enum perf_hw_id {
>  	PERF_COUNT_HW_BRANCH_MISSES		= 5,
>  	PERF_COUNT_HW_BUS_CYCLES		= 6,
>  	PERF_COUNT_HW_STALLED_CYCLES		= 7,
> +	PERF_COUNT_HW_NMI_WATCHDOG		= 8,
> 
>  	PERF_COUNT_HW_MAX,			/* non-ABI */
>  };
> Index: linux-2.6.git/kernel/watchdog.c
> =====================================================================
> --- linux-2.6.git.orig/kernel/watchdog.c
> +++ linux-2.6.git/kernel/watchdog.c
> @@ -191,7 +191,7 @@ static int is_softlockup(unsigned long t
>  #ifdef CONFIG_HARDLOCKUP_DETECTOR
>  static struct perf_event_attr wd_hw_attr = {
>  	.type		= PERF_TYPE_HARDWARE,
> -	.config		= PERF_COUNT_HW_CPU_CYCLES,
> +	.config		= PERF_COUNT_HW_NMI_WATCHDOG,
>  	.size		= sizeof(struct perf_event_attr),
>  	.pinned		= 1,
>  	.disabled	= 1,
> 
> -- 
>     Cyrill
> --
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