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Subject[PATCH v2 3/3] tracing: format non-nanosec times from tsc clock without a decimal point.
Date
With the addition of the "tsc" clock, formatting timestamps to look like
fractional seconds is misleading. Mark clocks as either in nanoseconds or
not, and format non-nanosecond timestamps as decimal integers.

Tested:
$ cd /sys/kernel/debug/tracing/
$ cat trace_clock
[local] global tsc
$ echo sched_switch > set_event
$ echo 1 > tracing_enabled ; sleep 0.0005 ; echo 0 > tracing_enabled
$ cat trace
<idle>-0 [000] 6330.555552: sched_switch: prev_comm=swapper prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=bash next_pid=29964 next_prio=120
sleep-29964 [000] 6330.555628: sched_switch: prev_comm=bash prev_pid=29964 prev_prio=120 prev_state=S ==> next_comm=swapper next_pid=0 next_prio=120
...
$ echo 1 > options/latency-format
$ cat trace
<idle>-0 0 4104553247us+: sched_switch: prev_comm=swapper prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=bash next_pid=29964 next_prio=120
sleep-29964 0 4104553322us+: sched_switch: prev_comm=bash prev_pid=29964 prev_prio=120 prev_state=S ==> next_comm=swapper next_pid=0 next_prio=120
...
$ echo tsc > trace_clock
$ cat trace
$ echo 1 > tracing_enabled ; sleep 0.0005 ; echo 0 > tracing_enabled
$ echo 0 > options/latency-format
$ cat trace
<idle>-0 [000] 16490053398357: sched_switch: prev_comm=swapper prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=bash next_pid=31128 next_prio=120
sleep-31128 [000] 16490053588518: sched_switch: prev_comm=bash prev_pid=31128 prev_prio=120 prev_state=S ==> next_comm=swapper next_pid=0 next_prio=120
...
echo 1 > options/latency-format
$ cat trace
<idle>-0 0 91557653238+: sched_switch: prev_comm=swapper prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=bash next_pid=31128 next_prio=120
sleep-31128 0 91557843399+: sched_switch: prev_comm=bash prev_pid=31128 prev_prio=120 prev_state=S ==> next_comm=swapper next_pid=0 next_prio=120
...

v2:
Move arch-specific bits out of generic code.

Google-Bug-Id: 6980623
Signed-off-by: David Sharp <dhsharp@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
---
arch/x86/include/asm/trace_clock.h | 2 +-
include/linux/ftrace_event.h | 6 +++
kernel/trace/trace.c | 15 +++++-
kernel/trace/trace.h | 4 --
kernel/trace/trace_output.c | 82 +++++++++++++++++++++++++-----------
5 files changed, 76 insertions(+), 33 deletions(-)

diff --git a/arch/x86/include/asm/trace_clock.h b/arch/x86/include/asm/trace_clock.h
index 0b1f391..4af2eb7 100644
--- a/arch/x86/include/asm/trace_clock.h
+++ b/arch/x86/include/asm/trace_clock.h
@@ -9,7 +9,7 @@
extern u64 notrace trace_clock_x86_tsc(void);

# define ARCH_TRACE_CLOCKS \
- { trace_clock_x86_tsc, "tsc" },
+ { trace_clock_x86_tsc, "tsc", .in_ns = 0 },

#endif

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 642928c..c760670 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -86,6 +86,12 @@ struct trace_iterator {
cpumask_var_t started;
};

+enum trace_iter_flags {
+ TRACE_FILE_LAT_FMT = 1,
+ TRACE_FILE_ANNOTATE = 2,
+ TRACE_FILE_TIME_IN_NS = 4,
+};
+

struct trace_event;

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4e26df3..3fe4c5b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -476,10 +476,11 @@ static const char *trace_options[] = {
static struct {
u64 (*func)(void);
const char *name;
+ int in_ns; /* is this clock in nanoseconds? */
} trace_clocks[] = {
- { trace_clock_local, "local" },
- { trace_clock_global, "global" },
- { trace_clock_counter, "counter" },
+ { trace_clock_local, "local", 1 },
+ { trace_clock_global, "global", 1 },
+ { trace_clock_counter, "counter", 0 },
ARCH_TRACE_CLOCKS
};

@@ -2425,6 +2426,10 @@ __tracing_open(struct inode *inode, struct file *file)
if (ring_buffer_overruns(iter->tr->buffer))
iter->iter_flags |= TRACE_FILE_ANNOTATE;

+ /* Output in nanoseconds only if we are using a clock in nanoseconds. */
+ if (trace_clocks[trace_clock_id].in_ns)
+ iter->iter_flags |= TRACE_FILE_TIME_IN_NS;
+
/* stop the trace while dumping */
tracing_stop();

@@ -3324,6 +3329,10 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
if (trace_flags & TRACE_ITER_LATENCY_FMT)
iter->iter_flags |= TRACE_FILE_LAT_FMT;

+ /* Output in nanoseconds only if we are using a clock in nanoseconds. */
+ if (trace_clocks[trace_clock_id].in_ns)
+ iter->iter_flags |= TRACE_FILE_TIME_IN_NS;
+
iter->cpu_file = cpu_file;
iter->tr = &global_trace;
mutex_init(&iter->mutex);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 55e1f7f..84fefed 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -409,10 +409,6 @@ void tracing_start_sched_switch_record(void);
int register_tracer(struct tracer *type);
void unregister_tracer(struct tracer *type);
int is_tracing_stopped(void);
-enum trace_file_type {
- TRACE_FILE_LAT_FMT = 1,
- TRACE_FILE_ANNOTATE = 2,
-};

extern cpumask_var_t __read_mostly tracing_buffer_mask;

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 123b189..c86d62a 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -610,24 +610,57 @@ lat_print_generic(struct trace_seq *s, struct trace_entry *entry, int cpu)
return trace_print_lat_fmt(s, entry);
}

-static unsigned long preempt_mark_thresh = 100;
+static unsigned long preempt_mark_thresh_us = 100;
+/* roughly the same at 2.0GHz: */
+static unsigned long preempt_mark_thresh_cycles = 200000;

static int
-lat_print_timestamp(struct trace_seq *s, u64 abs_usecs,
- unsigned long rel_usecs)
+lat_print_timestamp(struct trace_iterator *iter, u64 next_ts)
{
- return trace_seq_printf(s, " %4lldus%c: ", abs_usecs,
- rel_usecs > preempt_mark_thresh ? '!' :
- rel_usecs > 1 ? '+' : ' ');
+ int ret;
+ struct trace_seq *s = &iter->seq;
+ unsigned long verbose = trace_flags & TRACE_ITER_VERBOSE;
+ unsigned long in_ns = iter->iter_flags & TRACE_FILE_TIME_IN_NS;
+ unsigned long long abs_ts = iter->ts - iter->tr->time_start;
+ unsigned long long rel_ts = next_ts - iter->ts;
+ unsigned long mark_thresh;
+
+ if (in_ns) {
+ abs_ts = ns2usecs(abs_ts);
+ rel_ts = ns2usecs(rel_ts);
+ mark_thresh = preempt_mark_thresh_us;
+ } else
+ mark_thresh = preempt_mark_thresh_cycles;
+
+ if (verbose && in_ns) {
+ ret = trace_seq_printf(
+ s, "[%08llx] %lld.%03lldms (+%lld.%03lldms): ",
+ ns2usecs(iter->ts),
+ abs_ts / USEC_PER_MSEC,
+ abs_ts % USEC_PER_MSEC,
+ rel_ts / USEC_PER_MSEC,
+ rel_ts % USEC_PER_MSEC);
+ } else if (verbose && !in_ns) {
+ ret = trace_seq_printf(
+ s, "[%016llx] %lld (+%lld): ",
+ iter->ts, abs_ts, rel_ts);
+ } else { /* !verbose */
+ ret = trace_seq_printf(
+ s, " %4lld%s%c: ",
+ abs_ts,
+ in_ns ? "us" : "",
+ rel_ts > mark_thresh ? '!' :
+ rel_ts > 1 ? '+' : ' ');
+ }
+ return ret;
}

int trace_print_context(struct trace_iterator *iter)
{
struct trace_seq *s = &iter->seq;
struct trace_entry *entry = iter->ent;
- unsigned long long t = ns2usecs(iter->ts);
- unsigned long usec_rem = do_div(t, USEC_PER_SEC);
- unsigned long secs = (unsigned long)t;
+ unsigned long long t;
+ unsigned long secs, usec_rem;
char comm[TASK_COMM_LEN];
int ret;

@@ -644,8 +677,13 @@ int trace_print_context(struct trace_iterator *iter)
return 0;
}

- return trace_seq_printf(s, " %5lu.%06lu: ",
- secs, usec_rem);
+ if (iter->iter_flags & TRACE_FILE_TIME_IN_NS) {
+ t = ns2usecs(iter->ts);
+ usec_rem = do_div(t, USEC_PER_SEC);
+ secs = (unsigned long)t;
+ return trace_seq_printf(s, "%5lu.%06lu: ", secs, usec_rem);
+ } else
+ return trace_seq_printf(s, "%12llu: ", iter->ts);
}

int trace_print_lat_context(struct trace_iterator *iter)
@@ -659,36 +697,30 @@ int trace_print_lat_context(struct trace_iterator *iter)
*next_entry = trace_find_next_entry(iter, NULL,
&next_ts);
unsigned long verbose = (trace_flags & TRACE_ITER_VERBOSE);
- unsigned long abs_usecs = ns2usecs(iter->ts - iter->tr->time_start);
- unsigned long rel_usecs;
+

/* Restore the original ent_size */
iter->ent_size = ent_size;

if (!next_entry)
next_ts = iter->ts;
- rel_usecs = ns2usecs(next_ts - iter->ts);

if (verbose) {
char comm[TASK_COMM_LEN];

trace_find_cmdline(entry->pid, comm);

- ret = trace_seq_printf(s, "%16s %5d %3d %d %08x %08lx [%08llx]"
- " %ld.%03ldms (+%ld.%03ldms): ", comm,
- entry->pid, iter->cpu, entry->flags,
- entry->preempt_count, iter->idx,
- ns2usecs(iter->ts),
- abs_usecs / USEC_PER_MSEC,
- abs_usecs % USEC_PER_MSEC,
- rel_usecs / USEC_PER_MSEC,
- rel_usecs % USEC_PER_MSEC);
+ ret = trace_seq_printf(
+ s, "%16s %5d %3d %d %08x %08lx ",
+ comm, entry->pid, iter->cpu, entry->flags,
+ entry->preempt_count, iter->idx);
} else {
ret = lat_print_generic(s, entry, iter->cpu);
- if (ret)
- ret = lat_print_timestamp(s, abs_usecs, rel_usecs);
}

+ if (ret)
+ ret = lat_print_timestamp(iter, next_ts);
+
return ret;
}

--
1.7.7.3


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