[PATCH 0/9] Support branch counters in block annotation

kan.liang
2024-07-03T20:03:23Z

From: Kan Liang <kan.liang@linux.intel.com>

The branch counters logging (A.K.A LBR event logging) introduces a
per-counter indication of precise event occurrences in LBRs. It can
provide a means to attribute exposed retirement latency to combinations
of events across a block of instructions. It also provides a means of
attributing Timed LBR latencies to events.

The kernel support and basic perf tool support have been merged.
https://lore.kernel.org/lkml/20231025201626.3000228-1-kan.liang@linux.intel.com/

This series is to provide advanced perf tool support via adding the
branch counters information in block annotation. It can further
facilitate the analysis of branch blocks.

The patch 1 and 2 are to fix two existing issues of --total-cycles and
the branch counters feature.

The patch 3-9 are the advanced perf tool support.

Here are some examples.

perf annotation:

$perf record -e "{branch-instructions:ppp,branch-misses}:S" -j any,counter
$perf report --total-cycles --stdio

# To display the perf.data header info, please use --header/--header-only options.
#
#
# Total Lost Samples: 0
#
# Samples: 1M of events 'anon group { branch-instructions:ppp, branch-misses }'
# Event count (approx.): 1610046
#
# Branch counter abbr list:
# branch-instructions:ppp = A
# branch-misses = B
# '-' No event occurs
# '+' Event occurrences may be lost due to branch counter saturated
#
# Sampled Cycles% Sampled Cycles Avg Cycles% Avg Cycles Branch Counter [Program Block Range]
# ............... .............. ........... .......... ...................... ..
#
57.55% 2.5M 0.00% 3 |A |- | ...
25.27% 1.1M 0.00% 2 |AA |- | ...
15.61% 667.2K 0.00% 1 |A |- | ...
0.16% 6.9K 0.81% 575 |A |- | ...
0.16% 6.8K 1.38% 977 |AA |- | ...
0.16% 6.8K 0.04% 28 |AA |B | ...
0.15% 6.6K 1.33% 946 |A |- | ...
0.11% 4.5K 0.06% 46 |AAA+|- | ...

(The below output is in the TUI mode. Users can press 'B' to display
the Branch counter abbr list.)

Samples: 1M of events 'anon group { branch-instructions:ppp, branch-misses }',
4000 Hz, Event count (approx.):
f3 /home/sdp/test/tchain_edit [Percent: local period]
Percent │ IPC Cycle Branch Counter (Average IPC: 1.39, IPC Coverage: 29.4%)
│ 0000000000401755 <f3>:
0.00 0.00 │ endbr64
│ push %rbp
│ mov %rsp,%rbp
│ movl $0x0,-0x4(%rbp)
0.00 0.00 │1.33 3 |A |- | ↓ jmp 25
11.03 11.03 │ 11: mov -0x4(%rbp),%eax
│ and $0x1,%eax
│ test %eax,%eax
17.13 17.13 │2.41 1 |A |- | ↓ je 21
│ addl $0x1,-0x4(%rbp)
21.84 21.84 │2.22 2 |AA |- | ↓ jmp 25
17.13 17.13 │ 21: addl $0x1,-0x4(%rbp)
21.84 21.84 │ 25: cmpl $0x270f,-0x4(%rbp)
11.03 11.03 │0.61 3 |A |- | ↑ jle 11
│ nop
│ pop %rbp
0.00 0.00 │0.24 20 |AA |B | ← ret

perf script:

$perf script -F +brstackinsn,+brcntr

# Branch counter abbr list:
# branch-instructions:ppp = A
# branch-misses = B
# '-' No event occurs
# '+' Event occurrences may be lost due to branch counter saturated
tchain_edit 332203 3366329.405674: 53030 branch-instructions:ppp: 401781 f3+0x2c (home/sdp/test/tchain_edit)
f3+31:
0000000000401774 insn: eb 04 br_cntr: AA # PRED 5 cycles [5]
000000000040177a insn: 81 7d fc 0f 27 00 00
0000000000401781 insn: 7e e3 br_cntr: A # PRED 1 cycles [6] 2.00 IPC
0000000000401766 insn: 8b 45 fc
0000000000401769 insn: 83 e0 01
000000000040176c insn: 85 c0

$perf script -F +brstackinsn,+brcntr -v

tchain_edit 332203 3366329.405674: 53030 branch-instructions:ppp: 401781 f3+0x2c (/home/sdp/test/tchain_edit)
f3+31:
0000000000401774 insn: eb 04 br_cntr: branch-instructions:ppp 2 branch-misses 0 # PRED 5 cycles [5]
000000000040177a insn: 81 7d fc 0f 27 00 00
0000000000401781 insn: 7e e3 br_cntr: branch-instructions:ppp 1 branch-misses 0 # PRED 1 cycles [6] 2.00 IPC
0000000000401766 insn: 8b 45 fc
0000000000401769 insn: 83 e0 01
000000000040176c insn: 85 c0

Kan Liang (9):
perf report: Fix --total-cycles --stdio output error
perf report: Remove the first overflow check for branch counters
perf evlist: Save branch counters information
perf annotate: Save branch counters for each block
perf evsel: Assign abbr name for the branch counter events
perf report: Display the branch counter histogram
perf annotate: Display the branch counter histogram
perf script: Add branch counters
perf test: Add new test cases for the branch counter feature

tools/perf/Documentation/perf-report.txt | 1 +
tools/perf/Documentation/perf-script.txt | 2 +-
tools/perf/builtin-annotate.c | 13 +-
tools/perf/builtin-diff.c | 8 +-
tools/perf/builtin-report.c | 25 ++-
tools/perf/builtin-script.c | 69 +++++++-
tools/perf/builtin-top.c | 4 +-
tools/perf/tests/shell/record.sh | 17 +-
tools/perf/ui/browsers/annotate.c | 18 +-
tools/perf/ui/browsers/hists.c | 18 +-
tools/perf/util/annotate.c | 209 +++++++++++++++++++++--
tools/perf/util/annotate.h | 24 ++-
tools/perf/util/block-info.c | 66 ++++++-
tools/perf/util/block-info.h | 8 +-
tools/perf/util/branch.h | 1 +
tools/perf/util/disasm.c | 1 +
tools/perf/util/evlist.c | 66 +++++++
tools/perf/util/evlist.h | 2 +
tools/perf/util/evsel.c | 15 +-
tools/perf/util/evsel.h | 12 ++
tools/perf/util/hist.c | 5 +-
tools/perf/util/hist.h | 2 +-
tools/perf/util/machine.c | 3 +
23 files changed, 519 insertions(+), 70 deletions(-)

--
2.38.1