[tip:perf/core] perf trace: Do not print from time delta for interrupted syscall lines

From: tip-bot for Arnaldo Carvalho de Melo
Date: Wed Jan 24 2018 - 06:39:57 EST


Commit-ID: 507c6cdae5b2e7595ce50383fa5847540e398900
Gitweb: https://git.kernel.org/tip/507c6cdae5b2e7595ce50383fa5847540e398900
Author: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
AuthorDate: Mon, 22 Jan 2018 11:42:11 -0300
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Tue, 23 Jan 2018 09:51:51 -0300

perf trace: Do not print from time delta for interrupted syscall lines

We were calculating the delta from a in-flight syscall that got its
output interrupted by another syscall, which doesn't seem like useful
information, we will print the syscall duration (sys_exit - sys_enter)
when the raw_syscalls:sys_exit event happens.

The problem here is how we're consuming the multiple ring buffers,
without using the ordered_events code used by perf_session, which may
cause some reordering of syscalls for diferent CPUs, so just stop
printing that delta, to avoid things like:

# trace --print-sample -p 9626 -e futex
raw_syscalls:sys_enter 411967179.269 Timer 9609/9626 [2]
raw_syscalls:sys_enter 411967179.213 file:// Content 9609/9609 [3]
328.038 (18446744073709.496 ms): Timer/9626 futex(uaddr: 0x7fc0d4027044, op: WAIT|PRIV, utime: 0x7fc0b0ffdb50 ) ...
raw_syscalls:sys_exit 411967179.225 file:// Content 9609/9609 [3]
327.982 ( 0.012 ms): file:// Conten/9609 futex(uaddr: 0x7fc0d4027040, op: WAKE|PRIV, val: 1 ) = 1

This is a bandaid, we should better try and use the ordered_events code,
possibly with some refactoring prep work, but for now at least we don't
show those false long deltas for the lines ending in '...'.

Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Link: https://lkml.kernel.org/n/tip-q6xgsqrju1sr6ltud9kjjhmb@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/builtin-trace.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 322c2b1..ab00096 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -821,7 +821,7 @@ static size_t fprintf_duration(unsigned long t, bool calculated, FILE *fp)
size_t printed = fprintf(fp, "(");

if (!calculated)
- printed += fprintf(fp, " ? ");
+ printed += fprintf(fp, " ");
else if (duration >= 1.0)
printed += color_fprintf(fp, PERF_COLOR_RED, "%6.3f ms", duration);
else if (duration >= 0.01)
@@ -1556,10 +1556,9 @@ static void thread__update_stats(struct thread_trace *ttrace,
update_stats(stats, duration);
}

-static int trace__printf_interrupted_entry(struct trace *trace, struct perf_sample *sample)
+static int trace__printf_interrupted_entry(struct trace *trace)
{
struct thread_trace *ttrace;
- u64 duration;
size_t printed;

if (trace->current == NULL)
@@ -1570,9 +1569,7 @@ static int trace__printf_interrupted_entry(struct trace *trace, struct perf_samp
if (!ttrace->entry_pending)
return 0;

- duration = sample->time - ttrace->entry_time;
-
- printed = trace__fprintf_entry_head(trace, trace->current, duration, true, ttrace->entry_time, trace->output);
+ printed = trace__fprintf_entry_head(trace, trace->current, 0, false, ttrace->entry_time, trace->output);
printed += fprintf(trace->output, "%-70s) ...\n", ttrace->entry_str);
ttrace->entry_pending = false;

@@ -1627,7 +1624,7 @@ static int trace__sys_enter(struct trace *trace, struct perf_evsel *evsel,
}

if (!(trace->duration_filter || trace->summary_only || trace->min_stack))
- trace__printf_interrupted_entry(trace, sample);
+ trace__printf_interrupted_entry(trace);

ttrace->entry_time = sample->time;
msg = ttrace->entry_str;
@@ -1941,7 +1938,7 @@ static int trace__event_handler(struct trace *trace, struct perf_evsel *evsel,
}
}

- trace__printf_interrupted_entry(trace, sample);
+ trace__printf_interrupted_entry(trace);
trace__fprintf_tstamp(trace, sample->time, trace->output);

if (trace->trace_syscalls)