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Date: Tue, 29 Jun 2010 14:15:14 +0800
From: Lin Ming <ming.m.lin@...el.com>
To: Ingo Molnar <mingo@...e.hu>
Cc: Johannes Berg <johannes@...solutions.net>,
Peter Zijlstra <peterz@...radead.org>,
Greg KH <greg@...ah.com>,
Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
Frederic Weisbecker <fweisbec@...il.com>,
Paul Mundt <lethal@...ux-sh.org>,
"eranian@...il.com" <eranian@...il.com>,
"Gary.Mohr@...l.com" <Gary.Mohr@...l.com>,
"arjan@...ux.intel.com" <arjan@...ux.intel.com>,
"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
Paul Mackerras <paulus@...ba.org>,
"David S. Miller" <davem@...emloft.net>,
Russell King <rmk+kernel@....linux.org.uk>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
Will Deacon <will.deacon@....com>,
Maynard Johnson <mpjohn@...ibm.com>,
Carl Love <carll@...ibm.com>,
Kay Sievers <kay.sievers@...y.org>,
lkml <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [rfc] Describe events in a structured way via sysfs
On Fri, 2010-06-25 at 01:33 +0800, Ingo Molnar wrote:
> * Johannes Berg <johannes@...solutions.net> wrote:
>
> > On Thu, 2010-06-24 at 11:36 +0200, Ingo Molnar wrote:
> >
> > > That's probably best achieved via a TRACE_EVENT() variant, by passing in the
> > > sysfs location.
> > >
> > > It might even make sense to make this a part of TRACE_EVENT() itself and make
> > > 'NULL' the current default, non-sysfs-enumerated behavior. That way we can
> > > gradually (and non-intrusively) find all the right sysfs places for events.
> >
> > No, this doesn't work. A lot of events are multi-instance. Say you have an
> > event for each USB device. This event would have to show up in many places
> > in sysfs, and each trace_foo() invocation needs to get the struct device
> > pointer, not just the TRACE_EVENT() definition. Additionally, to
> > create/destroy the sysfs pieces we need something like init_trace_foo(dev)
> > and destroy_trace_foo(dev) be called when the sysfs points for the device
> > should be created/destroyed.
>
> Yes - but even this could be expressed via TRACE_EVENT(): by giving it a
> device-specific function pointer and then instantiating individual events from
> a single, central place in sysfs.
>
> That is the place where we already know where it ends up in sysfs, and where
> the event-specific function can match up whether that particular node belongs
> to it and whether an additional event directory should be created for that
> particular sysfs node.
>
> > The TRACE_EVENT() just defines the template, but such multi-instance events
> > really should be standardised in terms of their struct device (or maybe
> > kobject).
> >
> > I think that needs some TRACE_DEVICE_EVENT macro that creates the required
> > inlines etc, and including the init/destroy that are called when the event
> > should show up in sysfs.
> >
> > There's no way you can have the event show up in sysfs at the right spot
> > with _just_ a TRACE_EVENT macro, since at define time in the header file you
> > don't even have a valid struct device pointer.
>
> That would be another possible way to do it - to explicitly create the events
> directory. It looks a bit simpler as we wouldnt have to touch TRACE_EVENT()
> and because it directly expresses the 'this node has an events directory'
> property at the place where we create the device node.
Let me take i915 tracepoints as an example.
Do you mean something like below?
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 423dc90..9e7e4a0 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -28,6 +28,7 @@
*/
#include <linux/device.h>
+#include <linux/perf_event.h>
#include "drmP.h"
#include "drm.h"
#include "i915_drm.h"
@@ -413,7 +414,17 @@ int i965_reset(struct drm_device *dev, u8 flags)
static int __devinit
i915_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
{
- return drm_get_dev(pdev, ent, &driver);
+ struct kobject *kobj;
+ int ret;
+
+ ret = drm_get_dev(pdev, ent, &driver);
+
+ if (!ret) {
+ kobj = &pdev->dev.kobj;
+ perf_sys_register_tp(kobj, "i915");
+ }
+
+ return ret;
}
static void
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 716f99b..2a6d834 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1019,6 +1019,8 @@ extern int perf_swevent_get_recursion_context(void);
extern void perf_swevent_put_recursion_context(int rctx);
extern void perf_event_enable(struct perf_event *event);
extern void perf_event_disable(struct perf_event *event);
+
+extern void perf_sys_register_tp(struct kobject *kobj, char *tp_system);
#else
static inline void
perf_event_task_sched_in(struct task_struct *task) { }
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 403d180..1b85dad 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -5877,3 +5877,32 @@ static int __init perf_event_sysfs_init(void)
&perfclass_attr_group);
}
device_initcall(perf_event_sysfs_init);
+
+#define for_each_event(event, start, end) \
+ for (event = start; \
+ (unsigned long)event < (unsigned long)end; \
+ event++)
+
+extern struct ftrace_event_call __start_ftrace_events[];
+extern struct ftrace_event_call __stop_ftrace_events[];
+
+void perf_sys_register_tp(struct kobject *kobj, char *tp_system)
+{
+ struct ftrace_event_call *call;
+ struct kobject *events_kobj;
+
+ events_kobj = kobject_create_and_add("events", kobj);
+ if (!events_kobj)
+ return;
+
+ for_each_event(call, __start_ftrace_events, __stop_ftrace_events) {
+ if (call->class->system && !strcmp(call->class->system, tp_system)) {
+
+ /* create events/<tracepoint> */
+ kobject_create_and_add(call->name, events_kobj);
+
+ /* create events/<tracepoint>/enable, filter, format, id */
+ /* TBD ... */
+ }
+ }
+}
--
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