From: "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com>
To: rostedt@goodmis.org
Cc: linux-trace-devel@vger.kernel.org
Subject: [PATCH 02/15] tools lib traceevent: Add proper KBUFFER_TYPE_TIME_STAMP handling
Date: Thu, 25 Jun 2020 13:05:09 +0300 [thread overview]
Message-ID: <20200625100516.365338-3-tz.stoyanov@gmail.com> (raw)
In-Reply-To: <20200625100516.365338-1-tz.stoyanov@gmail.com>
From: Tom Zanussi <zanussi@kernel.org>
Kernel commit dc4e2801d400 (ring-buffer: Redefine the unimplemented
RINGBUF_TYPE_TIME_STAMP) changed the way the ring buffer timestamps
work - after that commit the previously unimplemented
RINGBUF_TYPE_TIME_STAMP type causes the time delta to be used as a
timestamp rather than a delta to be added to the timestamp.
The trace-cmd code didn't get updated to handle this, so misinterprets
the event data for this case, which causes a cascade of errors,
including trace-report not being able to identify synthetic (or any
other) events generated by the histogram code (which uses TIME_STAMP
mode). For example, the following triggers along with the trace-cmd
shown cause an UNKNOWN_EVENT error and trace-cmd report crash:
# echo 'wakeup_latency u64 lat pid_t pid char comm[16]' > /sys/kernel/debug/tracing/synthetic_events
# echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="ping"' > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
# echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0:onmatch(sched.sched_wakeup).trace(wakeup_latency,$wakeup_lat,next_pid,next_comm) if next_comm=="ping"' > /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
# echo 'hist:keys=comm,pid,lat:wakeup_lat=lat:sort=lat' > /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger
# trace-cmd record -e wakeup_latency -e sched_wakeup -f comm==\"ping\" ping localhost -c 5
# trace-cmd report
CPU 0 is empty
CPU 1 is empty
CPU 2 is empty
CPU 3 is empty
CPU 5 is empty
CPU 6 is empty
CPU 7 is empty
cpus=8
ug! no event found for type 0
[UNKNOWN TYPE 0]
ug! no event found for type 11520
Segmentation fault (core dumped)
After this patch we get the correct interpretation and the events are
shown properly:
# trace-cmd report
CPU 0 is empty
CPU 1 is empty
CPU 2 is empty
CPU 3 is empty
CPU 5 is empty
CPU 6 is empty
CPU 7 is empty
cpus=8
<idle>-0 [004] 23284.341392: sched_wakeup: ping:12031 [120] success=1 CPU:004
<idle>-0 [004] 23284.341464: wakeup_latency: lat=58, pid=12031, comm=ping
<idle>-0 [004] 23285.365303: sched_wakeup: ping:12031 [120] success=1 CPU:004
<idle>-0 [004] 23285.365382: wakeup_latency: lat=64, pid=12031, comm=ping
<idle>-0 [004] 23286.389290: sched_wakeup: ping:12031 [120] success=1 CPU:004
<idle>-0 [004] 23286.389378: wakeup_latency: lat=72, pid=12031, comm=ping
<idle>-0 [004] 23287.413213: sched_wakeup: ping:12031 [120] success=1 CPU:004
<idle>-0 [004] 23287.413291: wakeup_latency: lat=64, pid=12031, comm=ping
Link: http://lkml.kernel.org/r/1567628224.13841.4.camel@kernel.org
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
tools/lib/traceevent/kbuffer-parse.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/tools/lib/traceevent/kbuffer-parse.c b/tools/lib/traceevent/kbuffer-parse.c
index 583db99aee94..f1640d651c8a 100644
--- a/tools/lib/traceevent/kbuffer-parse.c
+++ b/tools/lib/traceevent/kbuffer-parse.c
@@ -361,6 +361,7 @@ translate_data(struct kbuffer *kbuf, void *data, void **rptr,
break;
case KBUFFER_TYPE_TIME_EXTEND:
+ case KBUFFER_TYPE_TIME_STAMP:
extend = read_4(kbuf, data);
data += 4;
extend <<= TS_SHIFT;
@@ -369,10 +370,6 @@ translate_data(struct kbuffer *kbuf, void *data, void **rptr,
*length = 0;
break;
- case KBUFFER_TYPE_TIME_STAMP:
- data += 12;
- *length = 0;
- break;
case 0:
*length = read_4(kbuf, data) - 4;
*length = (*length + 3) & ~3;
@@ -397,7 +394,11 @@ static unsigned int update_pointers(struct kbuffer *kbuf)
type_len = translate_data(kbuf, ptr, &ptr, &delta, &length);
- kbuf->timestamp += delta;
+ if (type_len == KBUFFER_TYPE_TIME_STAMP)
+ kbuf->timestamp = delta;
+ else
+ kbuf->timestamp += delta;
+
kbuf->index = calc_index(kbuf, ptr);
kbuf->next = kbuf->index + length;
@@ -454,7 +455,9 @@ static int __next_event(struct kbuffer *kbuf)
if (kbuf->next >= kbuf->size)
return -1;
type = update_pointers(kbuf);
- } while (type == KBUFFER_TYPE_TIME_EXTEND || type == KBUFFER_TYPE_PADDING);
+ } while (type == KBUFFER_TYPE_TIME_EXTEND ||
+ type == KBUFFER_TYPE_TIME_STAMP ||
+ type == KBUFFER_TYPE_PADDING);
return 0;
}
--
2.26.2
next prev parent reply other threads:[~2020-06-25 10:05 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-25 10:05 [PATCH 00/15] Synchronize libtraceevent with trace-cmd Tzvetomir Stoyanov (VMware)
2020-06-25 10:05 ` [PATCH 01/15] tools lib traceevent: Add --debug to trace-cmd report Tzvetomir Stoyanov (VMware)
2020-06-25 10:05 ` Tzvetomir Stoyanov (VMware) [this message]
2020-06-25 10:05 ` [PATCH 03/15] tools lib traceevent: Remove trace-cmd plugin handling routines Tzvetomir Stoyanov (VMware)
2020-06-25 10:05 ` [PATCH 04/15] tools lib traceevent: Move plugin options from trace-cmd to libtraceevent Tzvetomir Stoyanov (VMware)
2020-06-25 10:05 ` [PATCH 05/15] tools lib traceevent: Introduced new traceevent API, for adding new plugins directories Tzvetomir Stoyanov (VMware)
2020-06-25 10:05 ` [PATCH 06/15] tools lib traceevent: Add support for more printk format specifiers Tzvetomir Stoyanov (VMware)
2020-06-25 10:05 ` [PATCH 07/15] tools lib traceevent: Optimize pretty_print() function Tzvetomir Stoyanov (VMware)
2020-06-25 10:05 ` [PATCH 08/15] tools lib traceevent: Add plugin for tlb_flush Tzvetomir Stoyanov (VMware)
2020-06-25 10:05 ` [PATCH 09/15] tools lib traceevent: Add more SVM exit reasons Tzvetomir Stoyanov (VMware)
2020-07-02 17:37 ` [PATCH 00/15] Synchronize libtraceevent with trace-cmd Steven Rostedt
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