linux-kernel - Re: [PATCH v6 3/4] perf Documentation: add event parameters

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Message-ID: <20141222143943.GB29096@krava.brq.redhat.com>
Date:	Mon, 22 Dec 2014 15:39:43 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Paul Mackerras <paulus@...ba.org>, dev@...yps.com,
	peterz@...radead.org, hbabu@...ibm.com,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v6 3/4] perf Documentation: add event parameters

On Sun, Dec 21, 2014 at 11:49:26PM -0800, Sukadev Bhattiprolu wrote:
> From: Cody P Schafer <cody@...ux.vnet.ibm.com>
> 
> Event parameters are a basic way for partial events to be specified in
> sysfs with per-event names given to the fields that need to be filled in
> when using a particular event.
> 
> It is intended for supporting cases where the single 'cpu' parameter is
> insufficient. For example, POWER 8 has events for physical
> sockets/cores/cpus that are accessible from with virtual machines. To
> keep using the single 'cpu' parameter we'd need to perform a mapping
> between Linux's cpus and the physical machine's cpus (in this case
> Linux is running under a hypervisor). This isn't possible because
> bindings between our cpus and physical cpus may not be fixed, and we
> probably won't have a "cpu" on each physical cpu.
> 
> Changelog[v6]
> 	Update event description to explain how required parameters
> 	are displayed.
> 
> CC: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
> CC: Haren Myneni <hbabu@...ibm.com>
> CC: Cody P Schafer <dev@...yps.com>
> Signed-off-by: Cody P Schafer <cody@...ux.vnet.ibm.com>
> ---
>  Documentation/ABI/testing/sysfs-bus-event_source-devices-events | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-event_source-devices-events b/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
> index 20979f8..47ad2a1 100644
> --- a/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
> +++ b/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
> @@ -52,12 +52,18 @@ Description:	Per-pmu performance monitoring events specific to the running syste
>  			event=0x2abc
>  			event=0x423,inv,cmask=0x3
>  			domain=0x1,offset=0x8,starting_index=0xffff
> +			domain=0x1,offset=0x8,core=?
>  
>  		Each of the assignments indicates a value to be assigned to a
>  		particular set of bits (as defined by the format file
>  		corresponding to the <term>) in the perf_event structure passed
>  		to the perf_open syscall.
>  
> +		In the case of the last example, a value replacing "?" would
> +		need to be provided by the user selecting the particular event.
> +		This is referred to as "event parameterization". All
> +		non-numerical values indicate an event parameter.

I see.. here's the glitch ;-) I thought we agreed on forcing '?'
as the value for param events, not 'All non-numerical values'

thanks,
jirka
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