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Date: Fri, 6 Nov 2009 03:28:56 +0100
From: Frederic Weisbecker <fweisbec@...il.com>
To: Ingo Molnar <mingo@...e.hu>
Cc: LKML <linux-kernel@...r.kernel.org>,
Arjan van de Ven <arjan@...radead.org>,
Li Zefan <lizf@...fujitsu.com>,
Prasad <prasad@...ux.vnet.ibm.com>,
Alan Stern <stern@...land.harvard.edu>,
Peter Zijlstra <peterz@...radead.org>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
Steven Rostedt <rostedt@...dmis.org>,
Jan Kiszka <jan.kiszka@....de>,
Jiri Slaby <jirislaby@...il.com>, Avi Kivity <avi@...hat.com>,
Paul Mackerras <paulus@...ba.org>,
Mike Galbraith <efault@....de>,
Masami Hiramatsu <mhiramat@...hat.com>,
Paul Mundt <lethal@...ux-sh.org>,
Arjan van de Ven <arjan@...ux.intel.com>,
Ingo Molnar <mingo@...e.hu>,
Jan Kiszka <jan.kiszka@...mens.com>,
Frederic Weisbecker <fweisbec@...il.com>
Subject: [PATCH 1/7] perf/core: Provide a kernel-internal interface to get to performance counters
From: Arjan van de Ven <arjan@...radead.org>
There are reasons for kernel code to ask for, and use, performance
counters.
For example, in CPU freq governors this tends to be a good idea, but
there are other examples possible as well of course.
This patch adds the needed bits to do enable this functionality; they
have been tested in an experimental cpufreq driver that I'm working on,
and the changes are all that I needed to access counters properly.
[fweisbec@...il.com: added pid to perf_event_create_kernel_counter so
that we can profile a particular task too
TODO: Have a better error reporting, don't just return NULL in fail
case.]
v2: Remove the wrong comment about the fact
perf_event_create_kernel_counter must be called from a kernel
thread.
Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>
Acked-by: Peter Zijlstra <peterz@...radead.org>
Cc: "K.Prasad" <prasad@...ux.vnet.ibm.com>
Cc: Alan Stern <stern@...land.harvard.edu>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Jan Kiszka <jan.kiszka@...mens.com>
Cc: Jiri Slaby <jirislaby@...il.com>
Cc: Li Zefan <lizf@...fujitsu.com>
Cc: Avi Kivity <avi@...hat.com>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Mike Galbraith <efault@....de>
Cc: Masami Hiramatsu <mhiramat@...hat.com>
Cc: Paul Mundt <lethal@...ux-sh.org>
Cc: Jan Kiszka <jan.kiszka@....de>
Cc: Avi Kivity <avi@...hat.com>
LKML-Reference: <20090925122556.2f8bd939@...radead.org>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
---
include/linux/perf_event.h | 6 +++
kernel/perf_event.c | 75 +++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 80 insertions(+), 1 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index df9d964..fa151d4 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -744,6 +744,12 @@ extern int hw_perf_group_sched_in(struct perf_event *group_leader,
struct perf_cpu_context *cpuctx,
struct perf_event_context *ctx, int cpu);
extern void perf_event_update_userpage(struct perf_event *event);
+extern int perf_event_release_kernel(struct perf_event *event);
+extern struct perf_event *
+perf_event_create_kernel_counter(struct perf_event_attr *attr,
+ int cpu,
+ pid_t pid);
+extern u64 perf_event_read_value(struct perf_event *event);
struct perf_sample_data {
u64 type;
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 12b5ec3..02d4ff0 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -1725,6 +1725,26 @@ static int perf_release(struct inode *inode, struct file *file)
return 0;
}
+int perf_event_release_kernel(struct perf_event *event)
+{
+ struct perf_event_context *ctx = event->ctx;
+
+ WARN_ON_ONCE(ctx->parent_ctx);
+ mutex_lock(&ctx->mutex);
+ perf_event_remove_from_context(event);
+ mutex_unlock(&ctx->mutex);
+
+ mutex_lock(&event->owner->perf_event_mutex);
+ list_del_init(&event->owner_entry);
+ mutex_unlock(&event->owner->perf_event_mutex);
+ put_task_struct(event->owner);
+
+ free_event(event);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(perf_event_release_kernel);
+
static int perf_event_read_size(struct perf_event *event)
{
int entry = sizeof(u64); /* value */
@@ -1750,7 +1770,7 @@ static int perf_event_read_size(struct perf_event *event)
return size;
}
-static u64 perf_event_read_value(struct perf_event *event)
+u64 perf_event_read_value(struct perf_event *event)
{
struct perf_event *child;
u64 total = 0;
@@ -1761,6 +1781,7 @@ static u64 perf_event_read_value(struct perf_event *event)
return total;
}
+EXPORT_SYMBOL_GPL(perf_event_read_value);
static int perf_event_read_entry(struct perf_event *event,
u64 read_format, char __user *buf)
@@ -4638,6 +4659,58 @@ err_put_context:
return err;
}
+/**
+ * perf_event_create_kernel_counter
+ *
+ * @attr: attributes of the counter to create
+ * @cpu: cpu in which the counter is bound
+ * @pid: task to profile
+ */
+struct perf_event *
+perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
+ pid_t pid)
+{
+ struct perf_event *event;
+ struct perf_event_context *ctx;
+ int err;
+
+ /*
+ * Get the target context (task or percpu):
+ */
+
+ ctx = find_get_context(pid, cpu);
+ if (IS_ERR(ctx))
+ return NULL ;
+
+ event = perf_event_alloc(attr, cpu, ctx, NULL,
+ NULL, GFP_KERNEL);
+ err = PTR_ERR(event);
+ if (IS_ERR(event))
+ goto err_put_context;
+
+ event->filp = NULL;
+ WARN_ON_ONCE(ctx->parent_ctx);
+ mutex_lock(&ctx->mutex);
+ perf_install_in_context(ctx, event, cpu);
+ ++ctx->generation;
+ mutex_unlock(&ctx->mutex);
+
+ event->owner = current;
+ get_task_struct(current);
+ mutex_lock(¤t->perf_event_mutex);
+ list_add_tail(&event->owner_entry, ¤t->perf_event_list);
+ mutex_unlock(¤t->perf_event_mutex);
+
+ return event;
+
+err_put_context:
+ if (err < 0)
+ put_ctx(ctx);
+
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(perf_event_create_kernel_counter);
+
/*
* inherit a event from parent task to child task:
*/
--
1.6.2.3
--
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