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Merge pull request #961 from goldshtn/ugc-filters 

ugc: Add -M for minimum time and -F for text filtering
parents 5467ccf4 c325200c
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man/man8/ugc.8
View file @ 0ea2ffa7
......@@ -2,7 +2,7 @@
.SH NAME
ugc \- Trace garbage collection events in high-level languages.
.SH SYNOPSIS
.B ugc [-h] [-v] [-m] {java,python,ruby,node} pid
.B ugc [-h] [-v] [-m] [-M MINIMUM] [-F FILTER] {java,python,ruby,node} pid
.SH DESCRIPTION
This traces garbage collection events as they occur, including their duration
and any additional information (such as generation collected or type of GC)
......@@ -24,6 +24,18 @@ Print the resulting BPF program, for debugging purposes.
\-m
Print times in milliseconds. The default is microseconds.
.TP
\-M MINIMUM
Display only collections that are longer than this threshold. The value is
given in milliseconds. The default is to display all collections.
.TP
\-F FILTER
Display only collections whose textual description matches (contains) this
string. The default is to display all collections. Note that the filtering here
is performed in user-space, and not as part of the BPF program. This means that
if you have thousands of collection events, specifying this filter will not
reduce the amount of data that has to be transferred from the BPF program to
the user-space script.
.TP
{java,python,ruby,node}
The language to trace.
.TP
......@@ -39,16 +51,22 @@ Trace garbage collections in a specific Java process, and print GC times in
milliseconds:
#
.B ugc -m java 6004
.TP
Trace garbage collections in a specific Java process, and display them only if
they are longer than 10ms and have the string "Tenured" in their detailed
description:
#
.B ugc -M 10 -F Tenured java 6004
.SH FIELDS
.TP
START
The start time of the GC, in seconds from the beginning of the trace.
.TP
DESCRIPTION
The runtime-provided description of this garbage collection event.
.TP
TIME
The duration of the garbage collection event.
.TP
DESCRIPTION
The runtime-provided description of this garbage collection event.
.SH OVERHEAD
Garbage collection events, even if frequent, should not produce a considerable
overhead when traced because they are still not very common. Even hundreds of
......
tools/ugc.py
View file @ 0ea2ffa7
......@@ -4,7 +4,7 @@
# ugc Summarize garbage collection events in high-level languages.
# For Linux, uses BCC, eBPF.
#
# USAGE: ugc [-v] [-m] {java,python,ruby,node} pid
# USAGE: ugc [-v] [-m] [-M MSEC] [-F FILTER] {java,python,ruby,node} pid
#
# Copyright 2016 Sasha Goldshtein
# Licensed under the Apache License, Version 2.0 (the "License")
......@@ -20,6 +20,7 @@ import time
examples = """examples:
./ugc java 185 # trace Java GCs in process 185
./ugc ruby 1344 -m # trace Ruby GCs reporting in ms
./ugc -M 10 java 185 # trace only Java GCs longer than 10ms
"""
parser = argparse.ArgumentParser(
description="Summarize garbage collection events in high-level languages.",
......@@ -32,6 +33,10 @@ parser.add_argument("-v", "--verbose", action="store_true",
help="verbose mode: print the BPF program (for debugging purposes)")
parser.add_argument("-m", "--milliseconds", action="store_true",
help="report times in milliseconds (default is microseconds)")
parser.add_argument("-M", "--minimum", type=int, default=0,
help="display only GCs longer than this many milliseconds")
parser.add_argument("-F", "--filter", type=str,
help="display only GCs whose description contains this text")
args = parser.parse_args()
usdt = USDT(pid=args.pid)
......@@ -85,12 +90,16 @@ int trace_%s(struct pt_regs *ctx) {
return 0; // missed the entry event on this thread
}
elapsed = bpf_ktime_get_ns() - e->start_ns;
if (elapsed < %d) {
return 0;
}
event.elapsed_ns = elapsed;
%s
gcs.perf_submit(ctx, &event, sizeof(event));
return 0;
}
""" % (self.begin, self.begin_save, self.end, self.end_save)
""" % (self.begin, self.begin_save, self.end,
args.minimum * 1000000, self.end_save)
return text
def attach(self):
......@@ -187,7 +196,7 @@ bpf = BPF(text=program, usdt_contexts=[usdt])
print("Tracing garbage collections in %s process %d... Ctrl-C to quit." %
(args.language, args.pid))
time_col = "TIME (ms)" if args.milliseconds else "TIME (us)"
print("%-8s %-40s %-8s" % ("START", "DESCRIPTION", time_col))
print("%-8s %-8s %-40s" % ("START", time_col, "DESCRIPTION"))
class GCEvent(ct.Structure):
_fields_ = [
......@@ -207,9 +216,10 @@ def print_event(cpu, data, size):
event = ct.cast(data, ct.POINTER(GCEvent)).contents
elapsed = event.elapsed_ns/1000000 if args.milliseconds else \
event.elapsed_ns/1000
print("%-8.3f %-40s %-8.2f" % (time.time() - start_ts,
probes[event.probe_index].format(event),
elapsed))
description = probes[event.probe_index].format(event)
if args.filter and not args.filter in description:
return
print("%-8.3f %-8.2f %s" % (time.time() - start_ts, elapsed, description))
bpf["gcs"].open_perf_buffer(print_event)
while 1:
......
tools/ugc_example.txt
View file @ 0ea2ffa7
......@@ -8,45 +8,68 @@ the GC event is also provided.
For example, to trace all garbage collection events in a specific Node process:
# ./ugc node $(pidof node)
Tracing garbage collections in node process 3018... Ctrl-C to quit.
START DESCRIPTION TIME (us)
3.864 GC mark-sweep-compact 3189.00
4.937 GC scavenge 1254.00
4.940 GC scavenge 1657.00
4.943 GC scavenge 1171.00
4.949 GC scavenge 2216.00
4.954 GC scavenge 2515.00
4.960 GC scavenge 2243.00
4.966 GC scavenge 2410.00
4.976 GC scavenge 3003.00
4.986 GC scavenge 4174.00
4.994 GC scavenge 1508.00
5.003 GC scavenge 1966.00
5.010 GC scavenge 1636.00
5.022 GC scavenge 3564.00
5.035 GC scavenge 3275.00
5.045 GC incremental mark 157.00
5.049 GC mark-sweep-compact 3248.00
5.060 GC scavenge 4785.00
5.081 GC scavenge 6616.00
5.094 GC scavenge 8570.00
5.144 GC scavenge 456.00
7.188 GC scavenge 2345.00
7.227 GC scavenge 12054.00
7.253 GC scavenge 15626.00
7.304 GC scavenge 15329.00
7.384 GC scavenge 7168.00
7.411 GC scavenge 3794.00
7.414 GC incremental mark 123.00
7.430 GC mark-sweep-compact 7110.00
# ugc node $(pidof node)
Tracing garbage collections in node process 30012... Ctrl-C to quit.
START TIME (us) DESCRIPTION
1.500 1181.00 GC scavenge
1.505 1704.00 GC scavenge
1.509 1534.00 GC scavenge
1.515 1953.00 GC scavenge
1.519 2155.00 GC scavenge
1.525 2055.00 GC scavenge
1.530 2164.00 GC scavenge
1.536 2170.00 GC scavenge
1.541 2237.00 GC scavenge
1.547 1982.00 GC scavenge
1.551 2333.00 GC scavenge
1.557 2043.00 GC scavenge
1.561 2028.00 GC scavenge
1.573 3650.00 GC scavenge
1.580 4443.00 GC scavenge
1.604 6236.00 GC scavenge
1.615 8324.00 GC scavenge
1.659 11249.00 GC scavenge
1.678 16084.00 GC scavenge
1.747 15250.00 GC scavenge
1.937 191.00 GC incremental mark
2.001 63120.00 GC mark-sweep-compact
3.185 153.00 GC incremental mark
3.207 20847.00 GC mark-sweep-compact
^C
The above output shows some fairly long GCs, notably around 2 seconds in there
is a collection that takes over 60ms (mark-sweep-compact).
Occasionally, it might be useful to filter out collections that are very short,
or display only collections that have a specific description. The -M and -F
switches can be useful for this:
# ugc -F Tenured java $(pidof java)
Tracing garbage collections in java process 29907... Ctrl-C to quit.
START TIME (us) DESCRIPTION
0.360 4309.00 MarkSweepCompact Tenured Gen used=287528->287528 max=173408256->173408256
2.459 4232.00 MarkSweepCompact Tenured Gen used=287528->287528 max=173408256->173408256
4.648 4139.00 MarkSweepCompact Tenured Gen used=287528->287528 max=173408256->173408256
^C
# ugc -M 1 java $(pidof java)
Tracing garbage collections in java process 29907... Ctrl-C to quit.
START TIME (us) DESCRIPTION
0.160 3715.00 MarkSweepCompact Code Cache used=287528->3209472 max=173408256->251658240
0.160 3975.00 MarkSweepCompact Metaspace used=287528->3092104 max=173408256->18446744073709551615
0.160 4058.00 MarkSweepCompact Compressed Class Space used=287528->266840 max=173408256->1073741824
0.160 4110.00 MarkSweepCompact Eden Space used=287528->0 max=173408256->69337088
0.160 4159.00 MarkSweepCompact Survivor Space used=287528->0 max=173408256->8650752
0.160 4207.00 MarkSweepCompact Tenured Gen used=287528->287528 max=173408256->173408256
0.160 4289.00 used=0->0 max=0->0
^C
USAGE message:
# ./ugc -h
usage: ugc.py [-h] [-v] [-m] {java,python,ruby,node} pid
# ugc -h
usage: ugc.py [-h] [-v] [-m] [-M MINIMUM] [-F FILTER]
{java,python,ruby,node} pid
Summarize garbage collection events in high-level languages.
......@@ -60,7 +83,12 @@ optional arguments:
-v, --verbose verbose mode: print the BPF program (for debugging
purposes)
-m, --milliseconds report times in milliseconds (default is microseconds)
-M MINIMUM, --minimum MINIMUM
display only GCs longer than this many milliseconds
-F FILTER, --filter FILTER
display only GCs whose description contains this text
examples:
./ugc java 185 # trace Java GCs in process 185
./ugc ruby 1344 -m # trace Ruby GCs reporting in ms
./ugc -M 10 java 185 # trace only Java GCs longer than 10ms
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