[PATCH V3 10/17] perf tools: Save previous sample for LBR stitching approach

[kan . liang]

From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>

To retrieve the overwritten LBRs from previous sample for LBR stitching
approach, perf has to save the previous sample.

Only allocate the struct lbr_stitch once, when LBR stitching approach
is enabled and kernel supports hw_idx.

Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
---
 tools/perf/util/machine.c | 23 +++++++++++++++++++++++
 tools/perf/util/thread.c  |  1 +
 tools/perf/util/thread.h  | 16 ++++++++++++++++
 3 files changed, 40 insertions(+)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index f1661dd3ca69..d91e11bfc8ca 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -2261,6 +2261,21 @@ static int lbr_callchain_add_lbr_ip(struct thread *thread,
 	return 0;
 }
 
+static bool alloc_lbr_stitch(struct thread *thread)
+{
+	if (thread->lbr_stitch)
+		return true;
+
+	thread->lbr_stitch = calloc(1, sizeof(struct lbr_stitch));
+	if (!thread->lbr_stitch)
+		goto err;
+
+err:
+	pr_warning("Failed to allocate space for stitched LBRs. Disable LBR stitch\n");
+	thread->lbr_stitch_enable = false;
+	return false;
+}
+
 /*
  * Recolve LBR callstack chain sample
  * Return:
@@ -2277,6 +2292,7 @@ static int resolve_lbr_callchain_sample(struct thread *thread,
 {
 	struct ip_callchain *chain = sample->callchain;
 	int chain_nr = min(max_stack, (int)chain->nr), i;
+	struct lbr_stitch *lbr_stitch;
 	u64 branch_from = 0;
 	int err;
 
@@ -2289,6 +2305,13 @@ static int resolve_lbr_callchain_sample(struct thread *thread,
 	if (i == chain_nr)
 		return 0;
 
+	if (thread->lbr_stitch_enable && !sample->no_hw_idx &&
+	    alloc_lbr_stitch(thread)) {
+		lbr_stitch = thread->lbr_stitch;
+
+		memcpy(&lbr_stitch->prev_sample, sample, sizeof(*sample));
+	}
+
 	if (callchain_param.order == ORDER_CALLEE) {
 		/* Add kernel ip */
 		err = lbr_callchain_add_kernel_ip(thread, cursor, sample,
diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 1f080db23615..8d0da260c84c 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -111,6 +111,7 @@ void thread__delete(struct thread *thread)
 
 	exit_rwsem(&thread->namespaces_lock);
 	exit_rwsem(&thread->comm_lock);
+	thread__free_stitch_list(thread);
 	free(thread);
 }
 
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 95294050cff2..5fe239bd8f17 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -13,6 +13,7 @@
 #include <strlist.h>
 #include <intlist.h>
 #include "rwsem.h"
+#include "event.h"
 
 struct addr_location;
 struct map;
@@ -20,6 +21,10 @@ struct perf_record_namespaces;
 struct thread_stack;
 struct unwind_libunwind_ops;
 
+struct lbr_stitch {
+	struct perf_sample		prev_sample;
+};
+
 struct thread {
 	union {
 		struct rb_node	 rb_node;
@@ -49,6 +54,7 @@ struct thread {
 
 	/* LBR call stack stitch */
 	bool			lbr_stitch_enable;
+	struct lbr_stitch	*lbr_stitch;
 };
 
 struct machine;
@@ -145,4 +151,14 @@ static inline bool thread__is_filtered(struct thread *thread)
 	return false;
 }
 
+static inline void thread__free_stitch_list(struct thread *thread)
+{
+	struct lbr_stitch *lbr_stitch = thread->lbr_stitch;
+
+	if (!lbr_stitch)
+		return;
+
+	free(thread->lbr_stitch);
+}
+
 #endif	/* __PERF_THREAD_H */
-- 
2.17.1