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Subject[PATCH 2/2] perf tools: Construct LBR call chain
Date
From: Kan Liang <kan.liang@intel.com>

LBR call stack only has user callchain. It is output as
PERF_SAMPLE_BRANCH_STACK data format. For the kernel callchain, it's
still from PERF_SAMPLE_CALLCHAIN.
The perf tool has to handle both data sources to construct a
complete callstack.

Signed-off-by: Kan Liang <kan.liang@intel.com>
---
tools/perf/util/machine.c | 194 ++++++++++++++++++++++++++++++----------------
tools/perf/util/session.c | 41 ++++++++--
2 files changed, 163 insertions(+), 72 deletions(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 52e9490..f51014f 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1399,18 +1399,70 @@ struct branch_info *sample__resolve_bstack(struct perf_sample *sample,
return bi;
}

+static inline int __thread__resolve_callchain_sample(struct thread *thread,
+ u64 ip, u8 *cpumode,
+ struct symbol **parent,
+ struct addr_location *root_al,
+ struct addr_location *al)
+{
+ if (ip >= PERF_CONTEXT_MAX) {
+ switch (ip) {
+ case PERF_CONTEXT_HV:
+ *cpumode = PERF_RECORD_MISC_HYPERVISOR;
+ break;
+ case PERF_CONTEXT_KERNEL:
+ *cpumode = PERF_RECORD_MISC_KERNEL;
+ break;
+ case PERF_CONTEXT_USER:
+ *cpumode = PERF_RECORD_MISC_USER;
+ break;
+ default:
+ pr_debug("invalid callchain context: "
+ "%"PRId64"\n", (s64) ip);
+ /*
+ * It seems the callchain is corrupted.
+ * Discard all.
+ */
+ callchain_cursor_reset(&callchain_cursor);
+ return 1;
+ }
+ return 0;
+ }
+
+ al->filtered = 0;
+ thread__find_addr_location(thread, *cpumode,
+ MAP__FUNCTION, ip, al);
+ if (al->sym != NULL) {
+ if (sort__has_parent && !*parent &&
+ symbol__match_regex(al->sym, &parent_regex))
+ *parent = al->sym;
+ else if (have_ignore_callees && root_al &&
+ symbol__match_regex(al->sym, &ignore_callees_regex)) {
+ /* Treat this symbol as the root,
+ forgetting its callees. */
+ *root_al = *al;
+ callchain_cursor_reset(&callchain_cursor);
+ }
+ }
+
+ return callchain_cursor_append(&callchain_cursor,
+ ip, al->map, al->sym);
+}
+
static int thread__resolve_callchain_sample(struct thread *thread,
- struct ip_callchain *chain,
- struct symbol **parent,
- struct addr_location *root_al,
- int max_stack)
+ struct perf_evsel *evsel,
+ struct perf_sample *sample,
+ struct symbol **parent,
+ struct addr_location *root_al,
+ int max_stack)
{
+ struct ip_callchain *chain = sample->callchain;
u8 cpumode = PERF_RECORD_MISC_USER;
int chain_nr = min(max_stack, (int)chain->nr);
- int i;
- int j;
- int err;
+ int i, j, err = 0;
int skip_idx __maybe_unused;
+ int lbr = 0;
+ u64 ip;

callchain_cursor_reset(&callchain_cursor);

@@ -1419,74 +1471,81 @@ static int thread__resolve_callchain_sample(struct thread *thread,
return 0;
}

- /*
- * Based on DWARF debug information, some architectures skip
- * a callchain entry saved by the kernel.
- */
- skip_idx = arch_skip_callchain_idx(thread, chain);
+ if (evsel->attr.branch_sample_type & PERF_SAMPLE_BRANCH_CALL_STACK)
+ lbr = 1;

- for (i = 0; i < chain_nr; i++) {
- u64 ip;
- struct addr_location al;
+again:
+ /* LBR call stack */
+ if (lbr) {
+ struct branch_stack *lbr_stack = sample->branch_stack;
+ int lbr_nr = lbr_stack->nr;
+ int mix_chain_nr;

- if (callchain_param.order == ORDER_CALLEE)
- j = i;
- else
- j = chain->nr - i - 1;
+ for (i = 0; i < chain_nr; i++) {
+ if (chain->ips[i] == PERF_CONTEXT_USER)
+ break;
+ }

-#ifdef HAVE_SKIP_CALLCHAIN_IDX
- if (j == skip_idx)
- continue;
-#endif
- ip = chain->ips[j];
+ /* LBR only affects the user callchain */
+ if (i == chain_nr) {
+ lbr = 0;
+ goto again;
+ }

- if (ip >= PERF_CONTEXT_MAX) {
- switch (ip) {
- case PERF_CONTEXT_HV:
- cpumode = PERF_RECORD_MISC_HYPERVISOR;
- break;
- case PERF_CONTEXT_KERNEL:
- cpumode = PERF_RECORD_MISC_KERNEL;
- break;
- case PERF_CONTEXT_USER:
- cpumode = PERF_RECORD_MISC_USER;
- break;
- default:
- pr_debug("invalid callchain context: "
- "%"PRId64"\n", (s64) ip);
- /*
- * It seems the callchain is corrupted.
- * Discard all.
- */
- callchain_cursor_reset(&callchain_cursor);
- return 0;
- }
- continue;
+ mix_chain_nr = i + 2 + lbr_nr;
+ if (mix_chain_nr > PERF_MAX_STACK_DEPTH) {
+ pr_warning("corrupted callchain. skipping...\n");
+ return 0;
}

- al.filtered = 0;
- thread__find_addr_location(thread, cpumode,
- MAP__FUNCTION, ip, &al);
- if (al.sym != NULL) {
- if (sort__has_parent && !*parent &&
- symbol__match_regex(al.sym, &parent_regex))
- *parent = al.sym;
- else if (have_ignore_callees && root_al &&
- symbol__match_regex(al.sym, &ignore_callees_regex)) {
- /* Treat this symbol as the root,
- forgetting its callees. */
- *root_al = al;
- callchain_cursor_reset(&callchain_cursor);
+ for (j = 0; j < mix_chain_nr; j++) {
+ struct addr_location al;
+
+ if (callchain_param.order == ORDER_CALLEE) {
+ if (j < i + 2)
+ ip = chain->ips[j];
+ else
+ ip = lbr_stack->entries[j - i - 2].from;
+ } else {
+ if (j < lbr_nr)
+ ip = lbr_stack->entries[lbr_nr - j - 1].from;
+ else
+ ip = chain->ips[i + 1 - (j - lbr_nr)];
}
+ err = __thread__resolve_callchain_sample(thread,
+ ip, &cpumode, parent, root_al, &al);
+ if (err)
+ goto exit;
}
+ } else {

- err = callchain_cursor_append(&callchain_cursor,
- ip, al.map, al.sym);
- if (err)
- return err;
- }
+ /*
+ * Based on DWARF debug information, some architectures skip
+ * a callchain entry saved by the kernel.
+ */
+ skip_idx = arch_skip_callchain_idx(thread, chain);

- return 0;
+ for (i = 0; i < chain_nr; i++) {
+ struct addr_location al;
+
+ if (callchain_param.order == ORDER_CALLEE)
+ j = i;
+ else
+ j = chain->nr - i - 1;
+
+#ifdef HAVE_SKIP_CALLCHAIN_IDX
+ if (j == skip_idx)
+ continue;
+#endif
+ ip = chain->ips[j];
+ err = __thread__resolve_callchain_sample(thread,
+ ip, &cpumode, parent, root_al, &al);
+ if (err)
+ goto exit;
+ }
+ }
+exit:
+ return (err < 0) ? err : 0;
}

static int unwind_entry(struct unwind_entry *entry, void *arg)
@@ -1503,8 +1562,9 @@ int thread__resolve_callchain(struct thread *thread,
struct addr_location *root_al,
int max_stack)
{
- int ret = thread__resolve_callchain_sample(thread, sample->callchain,
- parent, root_al, max_stack);
+ int ret = thread__resolve_callchain_sample(thread, evsel,
+ sample, parent,
+ root_al, max_stack);
if (ret)
return ret;

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index f4478ce..fa476be 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -557,15 +557,45 @@ int perf_session_queue_event(struct perf_session *s, union perf_event *event,
return 0;
}

-static void callchain__printf(struct perf_sample *sample)
+static void callchain__printf(struct perf_evsel *evsel,
+ struct perf_sample *sample)
{
unsigned int i;
+ u64 total_nr, callchain_nr;
+ int lbr = 0;

- printf("... chain: nr:%" PRIu64 "\n", sample->callchain->nr);
+ total_nr = callchain_nr = sample->callchain->nr;

- for (i = 0; i < sample->callchain->nr; i++)
+ if (evsel->attr.branch_sample_type & PERF_SAMPLE_BRANCH_CALL_STACK)
+ lbr = 1;
+
+ if (lbr) {
+ struct branch_stack *lbr_stack = sample->branch_stack;
+
+ for (i = 0; i < callchain_nr; i++) {
+ if (sample->callchain->ips[i] == PERF_CONTEXT_USER)
+ break;
+ }
+
+ if (i != callchain_nr) {
+ total_nr = i + 1 + lbr_stack->nr;
+ callchain_nr = i + 1;
+ }
+ }
+
+ printf("... chain: nr:%" PRIu64 "\n", total_nr);
+
+ for (i = 0; i < callchain_nr + 1; i++)
printf("..... %2d: %016" PRIx64 "\n",
i, sample->callchain->ips[i]);
+
+ if (total_nr > callchain_nr) {
+ struct branch_stack *lbr_stack = sample->branch_stack;
+
+ for (i = 0; i < lbr_stack->nr; i++)
+ printf("..... %2d: %016" PRIx64 "\n",
+ (int)(i + callchain_nr + 1), lbr_stack->entries[i].from);
+ }
}

static void branch_stack__printf(struct perf_sample *sample)
@@ -691,9 +721,10 @@ static void dump_sample(struct perf_evsel *evsel, union perf_event *event,
sample_type = evsel->attr.sample_type;

if (sample_type & PERF_SAMPLE_CALLCHAIN)
- callchain__printf(sample);
+ callchain__printf(evsel, sample);

- if (sample_type & PERF_SAMPLE_BRANCH_STACK)
+ if ((sample_type & PERF_SAMPLE_BRANCH_STACK) &&
+ !(evsel->attr.branch_sample_type & PERF_SAMPLE_BRANCH_CALL_STACK))
branch_stack__printf(sample);

if (sample_type & PERF_SAMPLE_REGS_USER)
--
1.8.3.2


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