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#! /usr/bin/python3
# @lint-avoid-python-3-compatibility-imports
#
# ugc Summarize garbage collection events in high-level languages.
# For Linux, uses BCC, eBPF.
#
# USAGE: ugc [-v] [-m] [-M MSEC] [-F FILTER] {java,node,python,ruby} pid
#
# Copyright 2016 Sasha Goldshtein
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 19-Oct-2016 Sasha Goldshtein Created this.
from __future__ import print_function
import argparse
from bcc import BPF, USDT, utils
import ctypes as ct
import time
import os
languages = ["java", "node", "python", "ruby"]
examples = """examples:
./ugc -l java 185 # trace Java GCs in process 185
./ugc -l ruby 1344 -m # trace Ruby GCs reporting in ms
./ugc -M 10 -l java 185 # trace only Java GCs longer than 10ms
"""
parser = argparse.ArgumentParser(
description="Summarize garbage collection events in high-level languages.",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-l", "--language", choices=languages,
help="language to trace")
parser.add_argument("pid", type=int, help="process id to attach to")
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")
parser.add_argument("--ebpf", action="store_true",
help=argparse.SUPPRESS)
args = parser.parse_args()
usdt = USDT(pid=args.pid)
program = """
struct gc_event_t {
u64 probe_index;
u64 elapsed_ns;
u64 field1;
u64 field2;
u64 field3;
u64 field4;
char string1[32];
char string2[32];
};
struct entry_t {
u64 start_ns;
u64 field1;
u64 field2;
};
BPF_PERF_OUTPUT(gcs);
BPF_HASH(entry, u64, struct entry_t);
"""
class Probe(object):
def __init__(self, begin, end, begin_save, end_save, formatter):
self.begin = begin
self.end = end
self.begin_save = begin_save
self.end_save = end_save
self.formatter = formatter
def generate(self):
text = """
int trace_%s(struct pt_regs *ctx) {
u64 pid = bpf_get_current_pid_tgid();
struct entry_t e = {};
e.start_ns = bpf_ktime_get_ns();
%s
entry.update(&pid, &e);
return 0;
}
int trace_%s(struct pt_regs *ctx) {
u64 elapsed;
struct entry_t *e;
struct gc_event_t event = {};
u64 pid = bpf_get_current_pid_tgid();
e = entry.lookup(&pid);
if (!e) {
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,
args.minimum * 1000000, self.end_save)
return text
def attach(self):
usdt.enable_probe_or_bail(self.begin, "trace_%s" % self.begin)
usdt.enable_probe_or_bail(self.end, "trace_%s" % self.end)
def format(self, data):
return self.formatter(data)
probes = []
language = args.language
if not language:
language = utils.detect_language(languages, args.pid)
#
# Java
#
if language == "java":
# Oddly, the gc__begin/gc__end probes don't really have any useful
# information, while the mem__pool* ones do. There's also a bunch of
# probes described in the hotspot_gc*.stp file which aren't there
# when looking at a live Java process.
begin_save = """
bpf_usdt_readarg(6, ctx, &e.field1); // used bytes
bpf_usdt_readarg(8, ctx, &e.field2); // max bytes
"""
end_save = """
event.field1 = e->field1; // used bytes at start
event.field2 = e->field2; // max bytes at start
bpf_usdt_readarg(6, ctx, &event.field3); // used bytes at end
bpf_usdt_readarg(8, ctx, &event.field4); // max bytes at end
u64 manager = 0, pool = 0;
bpf_usdt_readarg(1, ctx, &manager); // ptr to manager name
bpf_usdt_readarg(3, ctx, &pool); // ptr to pool name
bpf_probe_read_user(&event.string1, sizeof(event.string1), (void *)manager);
bpf_probe_read_user(&event.string2, sizeof(event.string2), (void *)pool);
"""
def formatter(e):
"%s %s used=%d->%d max=%d->%d" % \
(e.string1, e.string2, e.field1, e.field3, e.field2, e.field4)
probes.append(Probe("mem__pool__gc__begin", "mem__pool__gc__end",
begin_save, end_save, formatter))
probes.append(Probe("gc__begin", "gc__end",
"", "", lambda _: "no additional info available"))
#
# Node
#
elif language == "node":
end_save = """
u32 gc_type = 0;
bpf_usdt_readarg(1, ctx, &gc_type);
event.field1 = gc_type;
"""
descs = {"GC scavenge": 1, "GC mark-sweep-compact": 2,
"GC incremental mark": 4, "GC weak callbacks": 8}
probes.append(Probe("gc__start", "gc__done", "", end_save,
lambda e: str.join(", ",
[desc for desc, val in descs.items()
if e.field1 & val != 0])))
#
# Python
#
elif language == "python":
begin_save = """
int gen = 0;
bpf_usdt_readarg(1, ctx, &gen);
e.field1 = gen;
"""
end_save = """
long objs = 0;
bpf_usdt_readarg(1, ctx, &objs);
event.field1 = e->field1;
event.field2 = objs;
"""
def formatter(event):
"gen %d GC collected %d objects" % \
(event.field1, event.field2)
probes.append(Probe("gc__start", "gc__done",
begin_save, end_save, formatter))
#
# Ruby
#
elif language == "ruby":
# Ruby GC probes do not have any additional information available.
probes.append(Probe("gc__mark__begin", "gc__mark__end",
"", "", lambda _: "GC mark stage"))
probes.append(Probe("gc__sweep__begin", "gc__sweep__end",
"", "", lambda _: "GC sweep stage"))
else:
print("No language detected; use -l to trace a language.")
exit(1)
for probe in probes:
program += probe.generate()
probe.attach()
if args.ebpf or args.verbose:
if args.verbose:
print(usdt.get_text())
print(program)
if args.ebpf:
exit()
bpf = BPF(text=program, usdt_contexts=[usdt])
print("Tracing garbage collections in %s process %d... Ctrl-C to quit." %
(language, args.pid))
time_col = "TIME (ms)" if args.milliseconds else "TIME (us)"
print("%-8s %-8s %-40s" % ("START", time_col, "DESCRIPTION"))
class GCEvent(ct.Structure):
_fields_ = [
("probe_index", ct.c_ulonglong),
("elapsed_ns", ct.c_ulonglong),
("field1", ct.c_ulonglong),
("field2", ct.c_ulonglong),
("field3", ct.c_ulonglong),
("field4", ct.c_ulonglong),
("string1", ct.c_char * 32),
("string2", ct.c_char * 32)
]
start_ts = time.time()
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
description = probes[event.probe_index].format(event)
if args.filter and args.filter not in description:
return
print("%-8.3f %-8.2f %s" % (time.time() - start_ts, elapsed, description))
bpf["gcs"].open_perf_buffer(print_event)
while 1:
try:
bpf.perf_buffer_poll()
except KeyboardInterrupt:
exit()
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