On Sat, 2010-07-17 at 08:20 +0800, Corey Ashford wrote:On 07/02/2010 01:06 AM, Lin Ming wrote:On Tue, 2010-06-29 at 18:26 +0800, Ingo Molnar wrote:...* Lin Ming<ming.m.lin@xxxxxxxxx> wrote:
Also, we can (optionally) consider 'generic', subsystem level events to
also show up under:
/sys/bus/pci/drivers/i915/events/
This would give a model to non-device-specific events to be listed one
level higher in the sysfs hierarchy.
This too would be done in the driver, not by generic code. It's generally
the driver which knows how the events should be categorized.
This is a bit difficult. I'd like not to touch TRACE_EVENT(). [...]
We can certainly start with the simpler variant - it's also the more common
case.
[...] How does the driver know if an event is 'generic' if TRACE_EVENT is
not touched?
Well, it's per driver code which creates the 'events' directory anyway, so
that code decides where to link things. It can link it to the per driver kobj
- or to the per subsys kobj.
I'd imagine something similar for wireless drivers as well - most
currently defined events would show up on a per device basis there.
Can you see practical problems with this scheme?
Not now. I may find some problems when write more detail code.
Ok. Feel free to post RFC patches (even if they are not fully complete yet),
so that we can see how things are progressing.
I suspect the best approach would be to try to figure out the right sysfs
placement for one or two existing driver tracepoints, so that we can see it
all in practice. (Obviously any changes to drivers will have to go via the
relevant driver maintainer tree(s).)
Well, take i915 tracepoints as an example, the sys structures as below
/sys/class/drm/card0/events/
|-- i915_gem_object_bind
| |-- enable
| |-- filter
| |-- format
| `-- id
Hi Lin,
Sorry for my late reply on this thread. I had missed these posts
earlier because I had an email filter that was set to look for messages
with "perf" in the subject, and so I missed this entire thread.
Sorry for my late reply too.
I have been busy with some other stuff. Hope I can send a more
functional patches this week.
With your example here, let's say I want to open this event with the
perf_events ABI... how would I go about doing that? Have you figured
out whether the caller would read the id and pass that into the
interface, or perhaps pass in the fd of the id file (or perhaps the fd
of the specific event directory).
Please just ignore my above example. Now I have some uncompleted new
patches to export hardware/software/tracepoint events via sysfs, like
below.
The event path is passed in with perf's "-e" option, for example
perf record -e /sys/kernel/events/page-faults --<some commands>
The caller reads config and type and pass them into perf_event_attr.
1. Hardware events
/sys/devices/system/cpu/cpu0...cpuN/events
|-- L1-dcache-load-misses ===> event name
| |-- config ===> config value for the event
| `-- type ===> event type
|-- cycles
| |-- config
| `-- type
.....
2. Software events
/sys/kernel/events
|-- page-faults
| |-- config
| `-- type
|-- context-switches
| |-- config
| `-- type
....
3. Tracepoint events
/sys/devices/pci0000:00/0000:00:02.0/events
|-- i915_gem_object_create
| |-- config
| `-- type
|-- i915_gem_object_bind
| |-- config
| `-- type
....
....
/sys/devices/system/kvm/kvm0/events
|-- kvm_entry
| |-- config
| `-- type
|-- kvm_hypercall
| |-- config
| `-- type
....
....
Also, I see the filter and format fields here. Would the caller write
to these fields to set them up? What's the format of the data that's
written to them? Would it be totally device dependent? It seems like
there should be a way for a user space tool to discover what can be
programmed into the filter and format fields.
Now only read-only event attributes(config and type) are exported.
I want to first make some minimal functional patches. Then to implement
the complex writable attributes.