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authorArjan van de Ven <arjan@infradead.org>2009-09-25 12:25:56 +0200
committerFrederic Weisbecker <fweisbec@gmail.com>2009-11-03 18:04:17 +0100
commitfb0459d75c1d0a4ba3cafdd2c754e7486968a676 (patch)
tree3e7a112cbf2feb144b3e1abbc5dfb186f77b8b50
parent0f8f86c7bdd1c954fbe153af437a0d91a6c5721a (diff)
perf/core: Provide a kernel-internal interface to get to performance counters
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@gmail.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@linux.intel.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: "K.Prasad" <prasad@linux.vnet.ibm.com> Cc: Alan Stern <stern@rowland.harvard.edu> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Jan Kiszka <jan.kiszka@siemens.com> Cc: Jiri Slaby <jirislaby@gmail.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Avi Kivity <avi@redhat.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Masami Hiramatsu <mhiramat@redhat.com> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Jan Kiszka <jan.kiszka@web.de> Cc: Avi Kivity <avi@redhat.com> LKML-Reference: <20090925122556.2f8bd939@infradead.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
-rw-r--r--include/linux/perf_event.h6
-rw-r--r--kernel/perf_event.c75
2 files changed, 80 insertions, 1 deletions
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index df9d964c15f..fa151d49a2e 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 12b5ec39bf9..02d4ff041b0 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(&current->perf_event_mutex);
+ list_add_tail(&event->owner_entry, &current->perf_event_list);
+ mutex_unlock(&current->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:
*/