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Message-ID: <Y1hLAT5L4ffmFhWe@kernel.org>
Date: Tue, 25 Oct 2022 17:45:53 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Adrian Hunter <adrian.hunter@...el.com>
Cc: Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
Namhyung Kim <namhyung@...nel.org>,
Ian Rogers <irogers@...gle.com>, linux-kernel@...r.kernel.org,
linux-perf-users@...r.kernel.org
Subject: Re: [PATCH] perf scripts python: intel-pt-events.py: Add ability
interleave output
Em Thu, Oct 20, 2022 at 06:25:09PM +0300, Adrian Hunter escreveu:
> Intel PT timestamps are not provided for every branch, let alone every
> instruction, so there can be many samples with the same timestamp. With
> per-cpu contexts, decoding is done for each CPU in turn, which can make it
> difficult to see what is happening on different CPUs at the same time.
> Currently the interleaving from perf script --itrace=i0ns is quite coarse
> grained. There are often long stretches executing on one CPU and nothing on
> another.
Thanks, applied.
- Arnaldo
> Some people are interested in seeing what happened on multiple CPUs before
> a crash to debug races etc.
>
> To improve perf script interleaving for parallel execution, the
> intel-pt-events.py script has been enhanced to enable interleaving the
> output with the same timestamp from different CPUs. It is understood that
> interleaving is not perfect or causal.
>
> Add parameter --interleave [<n>] to interleave sample output for the same
> timestamp so that no more than n samples for a CPU are displayed in a row.
> 'n' defaults to 4. Note this only affects the order of output, and only
> when the timestamp is the same.
>
> Example:
>
> $ perf script intel-pt-events.py --insn-trace --interleave 3
> ...
> bash 2267/2267 [004] 9323.692625625 563caa3c86f0 jz 0x563caa3c89c7 run_pending_traps+0x30 (/usr/bin/bash) IPC: 1.52 (38/25)
> bash 2267/2267 [004] 9323.692625625 563caa3c89c7 movq 0x118(%rsp), %rax run_pending_traps+0x307 (/usr/bin/bash)
> bash 2267/2267 [004] 9323.692625625 563caa3c89cf subq %fs:0x28, %rax run_pending_traps+0x30f (/usr/bin/bash)
> bash 2270/2270 [007] 9323.692625625 55dc58cabf02 jz 0x55dc58cabf48 unquoted_glob_pattern_p+0x102 (/usr/bin/bash) IPC: 1.56 (25/16)
> bash 2270/2270 [007] 9323.692625625 55dc58cabf04 cmp $0x5d, %al unquoted_glob_pattern_p+0x104 (/usr/bin/bash)
> bash 2270/2270 [007] 9323.692625625 55dc58cabf06 jnz 0x55dc58cabf10 unquoted_glob_pattern_p+0x106 (/usr/bin/bash)
> bash 2264/2264 [001] 9323.692625625 7fd556a4376c jbe 0x7fd556a43ac8 round_and_return+0x3fc (/usr/lib/x86_64-linux-gnu/libc.so.6) IPC: 4.30 (43/10)
> bash 2264/2264 [001] 9323.692625625 7fd556a43772 and $0x8, %edx round_and_return+0x402 (/usr/lib/x86_64-linux-gnu/libc.so.6)
> bash 2264/2264 [001] 9323.692625625 7fd556a43775 jnz 0x7fd556a43ac8 round_and_return+0x405 (/usr/lib/x86_64-linux-gnu/libc.so.6)
> bash 2267/2267 [004] 9323.692625625 563caa3c89d8 jnz 0x563caa3c8b11 run_pending_traps+0x318 (/usr/bin/bash)
> bash 2267/2267 [004] 9323.692625625 563caa3c89de add $0x128, %rsp run_pending_traps+0x31e (/usr/bin/bash)
> bash 2267/2267 [004] 9323.692625625 563caa3c89e5 popq %rbx run_pending_traps+0x325 (/usr/bin/bash)
> ...
>
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
> tools/perf/Documentation/perf-intel-pt.txt | 12 +++-
> tools/perf/scripts/python/intel-pt-events.py | 65 +++++++++++++++++++-
> 2 files changed, 74 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-intel-pt.txt b/tools/perf/Documentation/perf-intel-pt.txt
> index 92464a5d7eaf..7b6ccd2fa3bf 100644
> --- a/tools/perf/Documentation/perf-intel-pt.txt
> +++ b/tools/perf/Documentation/perf-intel-pt.txt
> @@ -189,8 +189,16 @@ There is also script intel-pt-events.py which provides an example of how to
> unpack the raw data for power events and PTWRITE. The script also displays
> branches, and supports 2 additional modes selected by option:
>
> - --insn-trace - instruction trace
> - --src-trace - source trace
> + - --insn-trace - instruction trace
> + - --src-trace - source trace
> +
> +The intel-pt-events.py script also has options:
> +
> + - --all-switch-events - display all switch events, not only the last consecutive.
> + - --interleave [<n>] - interleave sample output for the same timestamp so that
> + no more than n samples for a CPU are displayed in a row. 'n' defaults to 4.
> + Note this only affects the order of output, and only when the timestamp is the
> + same.
>
> As mentioned above, it is easy to capture too much data. One way to limit the
> data captured is to use 'snapshot' mode which is explained further below.
> diff --git a/tools/perf/scripts/python/intel-pt-events.py b/tools/perf/scripts/python/intel-pt-events.py
> index 6be7fd8fd615..08862a2582f4 100644
> --- a/tools/perf/scripts/python/intel-pt-events.py
> +++ b/tools/perf/scripts/python/intel-pt-events.py
> @@ -13,10 +13,12 @@
>
> from __future__ import print_function
>
> +import io
> import os
> import sys
> import struct
> import argparse
> +import contextlib
>
> from libxed import LibXED
> from ctypes import create_string_buffer, addressof
> @@ -39,6 +41,11 @@ glb_src = False
> glb_source_file_name = None
> glb_line_number = None
> glb_dso = None
> +glb_stash_dict = {}
> +glb_output = None
> +glb_output_pos = 0
> +glb_cpu = -1
> +glb_time = 0
>
> def get_optional_null(perf_dict, field):
> if field in perf_dict:
> @@ -70,6 +77,7 @@ def trace_begin():
> ap.add_argument("--insn-trace", action='store_true')
> ap.add_argument("--src-trace", action='store_true')
> ap.add_argument("--all-switch-events", action='store_true')
> + ap.add_argument("--interleave", type=int, nargs='?', const=4, default=0)
> global glb_args
> global glb_insn
> global glb_src
> @@ -94,11 +102,39 @@ def trace_begin():
> perf_set_itrace_options(perf_script_context, itrace)
>
> def trace_end():
> + if glb_args.interleave:
> + flush_stashed_output()
> print("End")
>
> def trace_unhandled(event_name, context, event_fields_dict):
> print(' '.join(['%s=%s'%(k,str(v))for k,v in sorted(event_fields_dict.items())]))
>
> +def stash_output():
> + global glb_stash_dict
> + global glb_output_pos
> + output_str = glb_output.getvalue()[glb_output_pos:]
> + n = len(output_str)
> + if n:
> + glb_output_pos += n
> + if glb_cpu not in glb_stash_dict:
> + glb_stash_dict[glb_cpu] = []
> + glb_stash_dict[glb_cpu].append(output_str)
> +
> +def flush_stashed_output():
> + global glb_stash_dict
> + while glb_stash_dict:
> + cpus = list(glb_stash_dict.keys())
> + # Output at most glb_args.interleave output strings per cpu
> + for cpu in cpus:
> + items = glb_stash_dict[cpu]
> + countdown = glb_args.interleave
> + while len(items) and countdown:
> + sys.stdout.write(items[0])
> + del items[0]
> + countdown -= 1
> + if not items:
> + del glb_stash_dict[cpu]
> +
> def print_ptwrite(raw_buf):
> data = struct.unpack_from("<IQ", raw_buf)
> flags = data[0]
> @@ -375,15 +411,40 @@ def do_process_event(param_dict):
> print_common_start(comm, sample, name)
> print_common_ip(param_dict, sample, symbol, dso)
>
> +def interleave_events(param_dict):
> + global glb_cpu
> + global glb_time
> + global glb_output
> + global glb_output_pos
> +
> + sample = param_dict["sample"]
> + glb_cpu = sample["cpu"]
> + ts = sample["time"]
> +
> + if glb_time != ts:
> + glb_time = ts
> + flush_stashed_output()
> +
> + glb_output_pos = 0
> + with contextlib.redirect_stdout(io.StringIO()) as glb_output:
> + do_process_event(param_dict)
> +
> + stash_output()
> +
> def process_event(param_dict):
> try:
> - do_process_event(param_dict)
> + if glb_args.interleave:
> + interleave_events(param_dict)
> + else:
> + do_process_event(param_dict)
> except broken_pipe_exception:
> # Stop python printing broken pipe errors and traceback
> sys.stdout = open(os.devnull, 'w')
> sys.exit(1)
>
> def auxtrace_error(typ, code, cpu, pid, tid, ip, ts, msg, cpumode, *x):
> + if glb_args.interleave:
> + flush_stashed_output()
> if len(x) >= 2 and x[0]:
> machine_pid = x[0]
> vcpu = x[1]
> @@ -403,6 +464,8 @@ def auxtrace_error(typ, code, cpu, pid, tid, ip, ts, msg, cpumode, *x):
> sys.exit(1)
>
> def context_switch(ts, cpu, pid, tid, np_pid, np_tid, machine_pid, out, out_preempt, *x):
> + if glb_args.interleave:
> + flush_stashed_output()
> if out:
> out_str = "Switch out "
> else:
> --
> 2.34.1
--
- Arnaldo
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