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SubjectRe: [rfc] Describe events in a structured way via sysfs
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> * Peter Zijlstra <peterz@infradead.org> wrote:
>
> > On Thu, 2010-05-20 at 16:12 -0700, Greg KH wrote:
>
> > > How deep in the device tree are you really going to be
> > > caring about? It sounds like the large majority of
> > > events are only going to be coming from the "system"
> > > type objects (cpu, nodes, memory, etc.) and very few
> > > would be from things that we consider a 'struct
> > > device' today (like a pci, usb, scsi, or input, etc.)
> >
> > The general noise I hear from the hardware people is
> > that we'll see more and more device-level stuff - bus
> > bridges/controller and actual devices (GPUs, NICs etc.)
> > will be wanting to export performance metrics.
>
> There's (much) more:
>
> - laptops want to provide power level/usage metrics,
>
> - we could express a lot of special, lower level
> (transport specific) disk IO stats via events as well -
> without having to push those stats to a higher level
> (where it might not make sense). Currently such kinds
> of stats/metrics are very device/subsystem specific
> way, if they are provided at all.
>
> Also, we already have quite a few per device tracepoints
> upstream. Here are a few examples:
>
> - GPU tracepoints (trace_i915_gem_request_submit(), etc.)
> - WIFI tracepoints (trace_iwlwifi_dev_ioread32(), etc.)
> - block tracepoints (trace_block_bio_complete())
>
> So these would be attached to:
>
> # GEM events of drm/card0:
> /sys/devices/pci0000:00/0000:00:02.0/drm/card0/events/i915_gem_request_submit/
>
> # Wifi-ioread events of wlan0:
> /sys/devices/pci0000:00/0000:00:1c.1/0000:03:00.0/net/wlan0/events/iwlwifi_dev_ioread32/
>
> # whole sdb disk events:
> /sys/block/sdb/events/block_bio_complete/
>
> # sdb1 partition events:
> /sys/block/sdb/sdb1/events/block_bio_complete/
>

The difficulty is how to know where each event should be attached to.

struct ftrace_event_call *call;

for_each_event(call, __start_ftrace_events, __stop_ftrace_events) {
/* where will this event be attached to? */
}

Any idea?

Thanks,
Lin Ming




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