Messages in this thread Patch in this message | | | From | Andi Kleen <> | Subject | [PATCH 7/9] perf, tools: Add overlap detection for report branch-call-stack mode | Date | Sat, 11 Jan 2014 11:42:57 -0800 |
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From: Andi Kleen <ak@linux.intel.com>
Add a simple heuristic to detect overlap of LBR entries and the call stack when in lbr-as-callgraph mode. The return address in the normal callstack is one off compared to the from entry in the branch stack. Handle this with a simple "assume call instruction is not longer than 8 bytes" heuristic. With that we can remove any redundant call in the callstack that is already in the branch stack.
Signed-off-by: Andi Kleen <ak@linux.intel.com> --- tools/perf/util/machine.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-)
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index 853639c..1f167fe 100644 --- a/tools/perf/util/machine.c +++ b/tools/perf/util/machine.c @@ -1349,6 +1349,7 @@ static int machine__resolve_callchain_sample(struct machine *machine, int chain_nr = min(max_stack, (int)chain->nr); int i; int err; + int first_call = 0; callchain_cursor_reset(&callchain_cursor); @@ -1362,8 +1363,6 @@ static int machine__resolve_callchain_sample(struct machine *machine, * Limitations for now: * - No extra filters * - No annotations (should annotate somehow) - * - When the sample is near the beginning of the function - * we may overlap with the real callstack. */ if (branch->nr > PERF_MAX_BRANCH_DEPTH) { @@ -1372,13 +1371,23 @@ static int machine__resolve_callchain_sample(struct machine *machine, } if (callchain_param.branch_callstack) { - int nr = min(max_stack, branch->nr); + int nr = min(max_stack, (int)branch->nr); struct branch_entry be[nr]; for (i = 0; i < nr; i++) { - if (callchain_param.order == ORDER_CALLEE) + if (callchain_param.order == ORDER_CALLEE) { be[i] = branch->entries[i]; - else + /* + * Check for overlap into the callchain. + * The return address is one off compared to + * the branch entry. To adjust for this + * assume the calling instruction is not longer + * than 8 bytes. + */ + if (be[i].from < chain->ips[first_call] && + be[i].from >= chain->ips[first_call] - 8) + first_call++; + } else be[i] = branch->entries[branch->nr - i - 1]; } @@ -1405,7 +1414,7 @@ static int machine__resolve_callchain_sample(struct machine *machine, return 0; } - for (i = 0; i < chain_nr; i++) { + for (i = first_call; i < chain_nr; i++) { u64 ip; if (callchain_param.order == ORDER_CALLEE) -- 1.8.3.1
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