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Subject[PATCH 53/60] perf thread: Save previous sample for LBR stitching approach
Date
From: Kan Liang <kan.liang@linux.intel.com>

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.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Pavel Gerasimov <pavel.gerasimov@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Vitaly Slobodskoy <vitaly.slobodskoy@intel.com>
Link: http://lore.kernel.org/lkml/20200319202517.23423-11-kan.liang@linux.intel.com
[ Use zalloc()/zfree() for thread->lbr_stitch ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/machine.c | 23 +++++++++++++++++++++++
tools/perf/util/thread.c | 1 +
tools/perf/util/thread.h | 12 ++++++++++++
3 files changed, 36 insertions(+)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index f9d69fce584a..a54ca09a1d00 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -2292,6 +2292,21 @@ 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 = zalloc(sizeof(*thread->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:
@@ -2308,6 +2323,7 @@ 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;

@@ -2320,6 +2336,13 @@ 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..34eb61cee6a4 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -5,6 +5,7 @@
#include <linux/refcount.h>
#include <linux/rbtree.h>
#include <linux/list.h>
+#include <linux/zalloc.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
@@ -13,6 +14,7 @@
#include <strlist.h>
#include <intlist.h>
#include "rwsem.h"
+#include "event.h"

struct addr_location;
struct map;
@@ -20,6 +22,10 @@ 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 +55,7 @@ struct thread {

/* LBR call stack stitch */
bool lbr_stitch_enable;
+ struct lbr_stitch *lbr_stitch;
};

struct machine;
@@ -145,4 +152,9 @@ static inline bool thread__is_filtered(struct thread *thread)
return false;
}

+static inline void thread__free_stitch_list(struct thread *thread)
+{
+ zfree(&thread->lbr_stitch);
+}
+
#endif /* __PERF_THREAD_H */
--
2.21.1
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