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Subject[tip:perfcounters/core] perf_counter: provide generic callchain bits
Commit-ID:  1254256f65ce3973462dc153e02b4f3a7e314e20
Gitweb: http://git.kernel.org/tip/1254256f65ce3973462dc153e02b4f3a7e314e20
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Mon, 30 Mar 2009 19:07:14 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 1 Apr 2009 11:33:38 +0200

perf_counter: provide generic callchain bits

Provide the generic callchain support bits. If hw_event->callchain is
set the arch specific perf_callchain() function is called upon to
provide a perf_callchain_entry structure filled with the current
callchain.

If it does so, it is added to the overflow output event.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20090330171024.254266860@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
include/linux/perf_counter.h | 13 ++++++++++++-
kernel/perf_counter.c | 27 +++++++++++++++++++++++++++
2 files changed, 39 insertions(+), 1 deletions(-)

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index edf5bfb..43083af 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -140,8 +140,9 @@ struct perf_counter_hw_event {
include_tid : 1, /* include the tid */
mmap : 1, /* include mmap data */
munmap : 1, /* include munmap data */
+ callchain : 1, /* add callchain data */

- __reserved_1 : 52;
+ __reserved_1 : 51;

__u32 extra_config_len;
__u32 __reserved_4;
@@ -219,6 +220,7 @@ enum perf_event_type {
PERF_EVENT_OVERFLOW = 1UL << 31,
__PERF_EVENT_IP = 1UL << 30,
__PERF_EVENT_TID = 1UL << 29,
+ __PERF_EVENT_CALLCHAIN = 1UL << 28,
};

#ifdef __KERNEL__
@@ -504,6 +506,15 @@ extern void perf_counter_mmap(unsigned long addr, unsigned long len,
extern void perf_counter_munmap(unsigned long addr, unsigned long len,
unsigned long pgoff, struct file *file);

+#define MAX_STACK_DEPTH 255
+
+struct perf_callchain_entry {
+ u64 nr;
+ u64 ip[MAX_STACK_DEPTH];
+};
+
+extern struct perf_callchain_entry *perf_callchain(struct pt_regs *regs);
+
#else
static inline void
perf_counter_task_sched_in(struct task_struct *task, int cpu) { }
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index d93e9dd..860cdc2 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1654,6 +1654,17 @@ void perf_counter_do_pending(void)
}

/*
+ * Callchain support -- arch specific
+ */
+
+struct perf_callchain_entry *
+__attribute__((weak))
+perf_callchain(struct pt_regs *regs)
+{
+ return NULL;
+}
+
+/*
* Output
*/

@@ -1764,6 +1775,8 @@ static void perf_output_simple(struct perf_counter *counter,
struct {
u32 pid, tid;
} tid_entry;
+ struct perf_callchain_entry *callchain = NULL;
+ int callchain_size = 0;

header.type = PERF_EVENT_OVERFLOW;
header.size = sizeof(header);
@@ -1781,6 +1794,17 @@ static void perf_output_simple(struct perf_counter *counter,
header.size += sizeof(tid_entry);
}

+ if (counter->hw_event.callchain) {
+ callchain = perf_callchain(regs);
+
+ if (callchain) {
+ callchain_size = (1 + callchain->nr) * sizeof(u64);
+
+ header.type |= __PERF_EVENT_CALLCHAIN;
+ header.size += callchain_size;
+ }
+ }
+
ret = perf_output_begin(&handle, counter, header.size, nmi);
if (ret)
return;
@@ -1791,6 +1815,9 @@ static void perf_output_simple(struct perf_counter *counter,
if (counter->hw_event.include_tid)
perf_output_put(&handle, tid_entry);

+ if (callchain)
+ perf_output_copy(&handle, callchain, callchain_size);
+
perf_output_end(&handle);
}


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