Messages in this thread | | | Date | Tue, 25 Jun 2013 18:56:39 +0200 | From | Robert Richter <> | Subject | Re: [PATCH v2 00/14] perf, persistent: Kernel updates for perf tool integration |
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On 24.06.13 12:22:00, Peter Zijlstra wrote: > On Tue, Jun 11, 2013 at 06:42:26PM +0200, Robert Richter wrote: > > Note that perf tools need to support the 'attr<num>' syntax that is > > added in a separate patch set. With it we are able to run perf tool > > commands to read persistent events, e.g.: > > where is this patch? I can't find it.
I posted it with that subject:
[PATCH 0/4] perf tools: Persistent events, changes for perf tool integration
> I also find attr<num>:<bit> a bit weird. So far we've used > <perf_event_attr::fieldname>:<bits>, so while initializing anonymous > unions is a bit difficult with 'older' GCCs and we cannot actually do: > > struct perf_event_attr { > ... > union { > u64 flags; > u64 disabled : 1, > ... > __reserved_1 : X; > } > ... > }; > > We could fake it in userspace by allowing things like: flags:23. It > would not be a much worse hack than attr<num>:<bit> I suppose.
A goal is to be able to entirely describe the complete attr structure with sysfs. perf tools should work out-of-the-box for every kind of event. For this particular case a 'flags' syntax would be ok, but not if you like to fill in other attr members.
With attr<num>:<bit> you are flexible to put in *everything* into attr. And for better readability there are abstractions as formats like:
/sys/bus/event_source/devices/persistent/format/persistent:attr5:23
Not sure if the event parser handles recursion already, but we could also support the 'flag' format you describe that way:
/sys/bus/event_source/devices/persistent/format/flags:attr5:0-63 /sys/bus/event_source/devices/persistent/format/persistent:flags:23
We could even list events for other pmus with small changes in the kernel, e.g:
/sys/bus/event_source/devices/persistent/format/type:attr0:0-31 /sys/bus/event_source/devices/persistent/events/some_tracepoint:type=2,config=<tp_id>
The example is a bit weird. But in general we can translate struct perf_event_attr to a string and vice versa. And perf tools understand how to set up every bit of the event attr structure.
-Robert
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