[RFC PATCH] Add timer-source of walltime for ftrace

Zhaolei
2009-08-17T09:20:42Z

We can add a timer-source for ftrace to support wall-time display.
It is based on Steven Rostedt <rostedt@goodmis.org>'s suggestion in:
http://lkml.org/lkml/2009/7/24/103

It needs to be applied on my patch of:
[PATCH v4 1/2] Add function to convert between calendar time and broken-down time for universal use
and
[PATCH v2 2/2] ftrace: Unify effect of writing to trace_options and option/*

We can get following output:
# cd /mnt/debugfs/tracing/
# ls options/*clock
options/global-clock options/local-clock options/walltime-clock
# echo sched_switch > current_tracer
# cat trace
# tracer: sched_switch
#
# TASK-PID CPU# TIMESTAMP FUNCTION
# | | | | |
bash-3560 [000] 694.242386: 3560:120:S + [000] 3560:120:S bash
bash-3560 [000] 694.242476: 3560:120:S + [000] 3560:120:S bash
bash-3560 [000] 694.242865: 3560:120:R + [000] 5:115:S events/0
bash-3560 [000] 694.242912: 3560:120:R ==> [000] 5:115:R events/0
events/0-5 [000] 694.243015: 5:115:R + [000] 3558:120:S sshd
events/0-5 [000] 694.243040: 5:115:S ==> [000] 3560:120:R bash
bash-3560 [000] 694.243312: 3560:120:S + [000] 3560:120:S bash
bash-3560 [000] 694.243374: 3560:120:S ==> [000] 3558:120:R sshd
...
# echo 1 > options/walltime-clock
# echo > trace
# cat trace
# tracer: sched_switch
#
# TASK-PID CPU# TIMESTAMP FUNCTION
# | | | | |
bash-3560 [000] 2009-08-17 23:58:22 3560:120:S + [000] 3560:120:S bash
bash-3560 [000] 2009-08-17 23:58:22 3560:120:R + [000] 5:115:S events/0
bash-3560 [000] 2009-08-17 23:58:22 3560:120:R ==> [000] 5:115:R events/0
events/0-5 [000] 2009-08-17 23:58:22 5:115:R + [000] 3558:120:S sshd
events/0-5 [000] 2009-08-17 23:58:22 5:115:S ==> [000] 3558:120:R sshd
sshd-3558 [000] 2009-08-17 23:58:22 3558:120:S ==> [000] 3560:120:R bash
bash-3560 [000] 2009-08-17 23:58:22 3560:120:S + [000] 3560:120:S bash
bash-3560 [000] 2009-08-17 23:58:22 3560:120:S + [000] 3560:120:S bash
...

Note:
It is only a prototype patch to for demostrate what is result looks like.
There still have many works to do(bug to fix) before apply.
For example, we need to add a hook(tracepoint) of xtime change event,
so we can update walltime's clock base then.
And maybe we need clear all events when changing clock-source, because old
clock value can't displayed correctly in new clock's format.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
---
include/linux/trace_clock.h | 1 +
kernel/trace/trace.c | 55 ++++++++++++++++++++++++++++++------------
kernel/trace/trace.h | 6 +++-
kernel/trace/trace_clock.c | 47 ++++++++++++++++++++++++++++++++++++
kernel/trace/trace_output.c | 20 ++++++++++++---
5 files changed, 107 insertions(+), 22 deletions(-)

diff --git a/include/linux/trace_clock.h b/include/linux/trace_clock.h
index 7a81303..322707e 100644
--- a/include/linux/trace_clock.h
+++ b/include/linux/trace_clock.h
@@ -15,5 +15,6 @@
extern u64 notrace trace_clock_local(void);
extern u64 notrace trace_clock(void);
extern u64 notrace trace_clock_global(void);
+extern u64 notrace trace_clock_walltime(void);

#endif /* _LINUX_TRACE_CLOCK_H */
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b7d873b..4474f7d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -263,8 +263,8 @@ static DECLARE_WAIT_QUEUE_HEAD(trace_wait);

/* trace_flags holds trace_options default values */
unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
- TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_SLEEP_TIME |
- TRACE_ITER_GRAPH_TIME;
+ TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_LOCAL_CLK |
+ TRACE_ITER_SLEEP_TIME | TRACE_ITER_GRAPH_TIME;

/**
* trace_wake_up - wake up tasks waiting for trace input
@@ -324,6 +324,8 @@ static const char *trace_options[] = {
"context-info",
"latency-format",
"global-clock",
+ "local-clock",
+ "walltime-clock",
"sleep-time",
"graph-time",
NULL
@@ -1423,8 +1425,17 @@ static void print_lat_help_header(struct seq_file *m)

static void print_func_help_header(struct seq_file *m)
{
- seq_puts(m, "# TASK-PID CPU# TIMESTAMP FUNCTION\n");
- seq_puts(m, "# | | | | |\n");
+ if (trace_flags & TRACE_ITER_WALLTIME_CLK) {
+ seq_puts(m, "# TASK-PID CPU# "
+ " TIMESTAMP FUNCTION\n");
+ seq_puts(m, "# | | | "
+ " | |\n");
+ } else {
+ seq_puts(m, "# TASK-PID CPU# "
+ " TIMESTAMP FUNCTION\n");
+ seq_puts(m, "# | | | "
+ " | |\n");
+ }
}

@@ -2151,30 +2162,42 @@ static int set_tracer_option(struct tracer *trace, char *cmp, int neg)

static void set_tracer_flags(unsigned int mask, int enabled)
{
+ u64 (*clkfunc)(void) = NULL;
+
/* do nothing if flag is already set */
if (!!(trace_flags & mask) == !!enabled)
return;

- if (enabled)
- trace_flags |= mask;
- else
- trace_flags &= ~mask;
+ if (mask == TRACE_ITER_GLOBAL_CLK)
+ clkfunc = trace_clock_global;
+ if (mask == TRACE_ITER_LOCAL_CLK)
+ clkfunc = trace_clock_local;
+ if (mask == TRACE_ITER_WALLTIME_CLK)
+ clkfunc = trace_clock_walltime;

- if (mask == TRACE_ITER_GLOBAL_CLK) {
- u64 (*func)(void);
+ if (clkfunc) {
+ if (!enabled)
+ return;

- if (enabled)
- func = trace_clock_global;
- else
- func = trace_clock_local;
+ trace_flags &= ~TRACE_ITER_GLOBAL_CLK;
+ trace_flags &= ~TRACE_ITER_LOCAL_CLK;
+ trace_flags &= ~TRACE_ITER_WALLTIME_CLK;
+ trace_flags |= mask;

mutex_lock(&trace_types_lock);
- ring_buffer_set_clock(global_trace.buffer, func);
+ ring_buffer_set_clock(global_trace.buffer, clkfunc);

if (max_tr.buffer)
- ring_buffer_set_clock(max_tr.buffer, func);
+ ring_buffer_set_clock(max_tr.buffer, clkfunc);
mutex_unlock(&trace_types_lock);
+
+ return;
}
+
+ if (enabled)
+ trace_flags |= mask;
+ else
+ trace_flags &= ~mask;
}

static ssize_t
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 606073c..02ffa4c 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -675,8 +675,10 @@ enum trace_iterator_flags {
TRACE_ITER_CONTEXT_INFO = 0x20000, /* Print pid/cpu/time */
TRACE_ITER_LATENCY_FMT = 0x40000,
TRACE_ITER_GLOBAL_CLK = 0x80000,
- TRACE_ITER_SLEEP_TIME = 0x100000,
- TRACE_ITER_GRAPH_TIME = 0x200000,
+ TRACE_ITER_LOCAL_CLK = 0x100000,
+ TRACE_ITER_WALLTIME_CLK = 0x200000,
+ TRACE_ITER_SLEEP_TIME = 0x400000,
+ TRACE_ITER_GRAPH_TIME = 0x800000,
};

/*
diff --git a/kernel/trace/trace_clock.c b/kernel/trace/trace_clock.c
index b588fd8..53ced3e 100644
--- a/kernel/trace/trace_clock.c
+++ b/kernel/trace/trace_clock.c
@@ -107,3 +107,50 @@ u64 notrace trace_clock_global(void)

return now;
}
+
+/* value of time_t when traceclock is 0 */
+static struct timespec base_walltime;
+
+u64 notrace trace_clock_walltime(void)
+{
+ u32 remainder;
+ return base_walltime.tv_sec + div_u64_rem(
+ trace_clock() + base_walltime.tv_nsec,
+ NSEC_PER_SEC, &remainder);
+}
+
+static int __init walltime_init(void)
+{
+ unsigned long flags;
+ struct timespec ts;
+ u64 traceclock;
+ u32 remainder;
+
+ local_irq_save(flags);
+
+ getnstimeofday(&ts);
+ traceclock = trace_clock();
+
+ if (traceclock > ts.tv_nsec) {
+ base_walltime.tv_sec = ts.tv_sec - div_u64_rem(
+ traceclock - ts.tv_nsec + NSEC_PER_SEC - 1,
+ NSEC_PER_SEC, &remainder);
+
+ /*
+ * base_walltime.tv_nsec =
+ * (NSEC_PER_SEC - (traceclock - ts.tv_nsec) %
+ * NSEC_PER_SEC) % NSEC_PER_SEC;
+ */
+ div_u64_rem(traceclock - ts.tv_nsec, NSEC_PER_SEC, &remainder);
+ base_walltime.tv_nsec = remainder ?
+ NSEC_PER_SEC - remainder : 0;
+ } else {
+ base_walltime.tv_sec = ts.tv_sec;
+ base_walltime.tv_nsec = ts.tv_nsec - traceclock;
+ }
+
+ local_irq_restore(flags);
+ return 0;
+}
+
+device_initcall_sync(walltime_init);
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index e0c2545..0419b37 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -501,15 +501,27 @@ 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;
char comm[TASK_COMM_LEN];

trace_find_cmdline(entry->pid, comm);

- return trace_seq_printf(s, "%16s-%-5d [%03d] %5lu.%06lu: ",
+ if (trace_flags & TRACE_ITER_WALLTIME_CLK) {
+ struct tm tm;
+ time_to_tm(iter->ts, 0, &tm);
+ return trace_seq_printf(s, "%16s-%-5d [%03d] "
+ "%04ld-%02d-%02d "
+ "%02d:%02d:%02d ",
+ comm, entry->pid, iter->cpu,
+ tm.tm_year + 1900, tm.tm_mon + 1,
+ tm.tm_mday, tm.tm_hour, tm.tm_min,
+ tm.tm_sec);
+ } else {
+ unsigned long long t = ns2usecs(iter->ts);
+ unsigned long usec_rem = do_div(t, USEC_PER_SEC);
+ unsigned long secs = (unsigned long)t;
+ return trace_seq_printf(s, "%16s-%-5d [%03d] %5lu.%06lu: ",
comm, entry->pid, iter->cpu, secs, usec_rem);
+ }
}

int trace_print_lat_context(struct trace_iterator *iter)
--
1.5.5.3