[PATCH 2/3] perf script: Fix off by one in brstackinsn IPC computation

Andi Kleen
2019-07-11T18:19:32Z

From: Andi Kleen <ak@linux.intel.com>

When we hit the end of a program block, need to count the last instruction
too for the IPC computation. This caused large errors for small blocks.

% perf script -b ls / > /dev/null

Before:

% perf script -F +brstackinsn --xed
...
00007f94c9ac70d8 jz 0x7f94c9ac70e3 # PRED 3 cycles [36] 4.33 IPC
00007f94c9ac70e3 testb $0x20, 0x31d(%rbx)
00007f94c9ac70ea jnz 0x7f94c9ac70b0
00007f94c9ac70ec testb $0x8, 0x205ad(%rip)
00007f94c9ac70f3 jz 0x7f94c9ac6ff0 # PRED 1 cycles [37] 3.00 IPC

After:

% perf script -F +brstackinsn --xed
...
00007f94c9ac70d8 jz 0x7f94c9ac70e3 # PRED 3 cycles [15] 4.67 IPC
00007f94c9ac70e3 testb $0x20, 0x31d(%rbx)
00007f94c9ac70ea jnz 0x7f94c9ac70b0
00007f94c9ac70ec testb $0x8, 0x205ad(%rip)
00007f94c9ac70f3 jz 0x7f94c9ac6ff0 # PRED 1 cycles [16] 4.00 IPC

Suggested-by: Denis Bakhvalov <denis.bakhvalov@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
tools/perf/builtin-script.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index 2f6232f1bfdc..9a63cb3442a9 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -1059,7 +1059,7 @@ static int perf_sample__fprintf_brstackinsn(struct perf_sample *sample,

printed += ip__fprintf_sym(ip, thread, x.cpumode, x.cpu, &lastsym, attr, fp);
if (ip == end) {
- printed += ip__fprintf_jump(ip, &br->entries[i], &x, buffer + off, len - off, insn, fp,
+ printed += ip__fprintf_jump(ip, &br->entries[i], &x, buffer + off, len - off, ++insn, fp,
&total_cycles);
if (PRINT_FIELD(SRCCODE))
printed += print_srccode(thread, x.cpumode, ip);
--
2.20.1