1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
|
# Copyright 2021 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import ctypes
import logging
import os
import re
from typing import Optional
from synapse.metrics import REGISTRY, GaugeMetricFamily
logger = logging.getLogger(__name__)
def _setup_jemalloc_stats():
"""Checks to see if jemalloc is loaded, and hooks up a collector to record
statistics exposed by jemalloc.
"""
# Try to find the loaded jemalloc shared library, if any. We need to
# introspect into what is loaded, rather than loading whatever is on the
# path, as if we load a *different* jemalloc version things will seg fault.
# We look in `/proc/self/maps`, which only exists on linux.
if not os.path.exists("/proc/self/maps"):
logger.debug("Not looking for jemalloc as no /proc/self/maps exist")
return
# We're looking for a path at the end of the line that includes
# "libjemalloc".
regex = re.compile(r"/\S+/libjemalloc.*$")
jemalloc_path = None
with open("/proc/self/maps") as f:
for line in f:
match = regex.search(line.strip())
if match:
jemalloc_path = match.group()
if not jemalloc_path:
# No loaded jemalloc was found.
logger.debug("jemalloc not found")
return
logger.debug("Found jemalloc at %s", jemalloc_path)
jemalloc = ctypes.CDLL(jemalloc_path)
def _mallctl(
name: str, read: bool = True, write: Optional[int] = None
) -> Optional[int]:
"""Wrapper around `mallctl` for reading and writing integers to
jemalloc.
Args:
name: The name of the option to read from/write to.
read: Whether to try and read the value.
write: The value to write, if given.
Returns:
The value read if `read` is True, otherwise None.
Raises:
An exception if `mallctl` returns a non-zero error code.
"""
input_var = None
input_var_ref = None
input_len_ref = None
if read:
input_var = ctypes.c_size_t(0)
input_len = ctypes.c_size_t(ctypes.sizeof(input_var))
input_var_ref = ctypes.byref(input_var)
input_len_ref = ctypes.byref(input_len)
write_var_ref = None
write_len = ctypes.c_size_t(0)
if write is not None:
write_var = ctypes.c_size_t(write)
write_len = ctypes.c_size_t(ctypes.sizeof(write_var))
write_var_ref = ctypes.byref(write_var)
# The interface is:
#
# int mallctl(
# const char *name,
# void *oldp,
# size_t *oldlenp,
# void *newp,
# size_t newlen
# )
#
# Where oldp/oldlenp is a buffer where the old value will be written to
# (if not null), and newp/newlen is the buffer with the new value to set
# (if not null). Note that they're all references *except* newlen.
result = jemalloc.mallctl(
name.encode("ascii"),
input_var_ref,
input_len_ref,
write_var_ref,
write_len,
)
if result != 0:
raise Exception("Failed to call mallctl")
if input_var is None:
return None
return input_var.value
def _jemalloc_refresh_stats() -> None:
"""Request that jemalloc updates its internal statistics. This needs to
be called before querying for stats, otherwise it will return stale
values.
"""
try:
_mallctl("epoch", read=False, write=1)
except Exception as e:
logger.warning("Failed to reload jemalloc stats: %s", e)
class JemallocCollector:
"""Metrics for internal jemalloc stats."""
def collect(self):
_jemalloc_refresh_stats()
g = GaugeMetricFamily(
"jemalloc_stats_app_memory_bytes",
"The stats reported by jemalloc",
labels=["type"],
)
# Read the relevant global stats from jemalloc. Note that these may
# not be accurate if python is configured to use its internal small
# object allocator (which is on by default, disable by setting the
# env `PYTHONMALLOC=malloc`).
#
# See the jemalloc manpage for details about what each value means,
# roughly:
# - allocated ─ Total number of bytes allocated by the app
# - active ─ Total number of bytes in active pages allocated by
# the application, this is bigger than `allocated`.
# - resident ─ Maximum number of bytes in physically resident data
# pages mapped by the allocator, comprising all pages dedicated
# to allocator metadata, pages backing active allocations, and
# unused dirty pages. This is bigger than `active`.
# - mapped ─ Total number of bytes in active extents mapped by the
# allocator.
# - metadata ─ Total number of bytes dedicated to jemalloc
# metadata.
for t in (
"allocated",
"active",
"resident",
"mapped",
"metadata",
):
try:
value = _mallctl(f"stats.{t}")
except Exception as e:
# There was an error fetching the value, skip.
logger.warning("Failed to read jemalloc stats.%s: %s", t, e)
continue
g.add_metric([t], value=value)
yield g
REGISTRY.register(JemallocCollector())
logger.debug("Added jemalloc stats")
def setup_jemalloc_stats():
"""Try to setup jemalloc stats, if jemalloc is loaded."""
try:
_setup_jemalloc_stats()
except Exception as e:
# This should only happen if we find the loaded jemalloc library, but
# fail to load it somehow (e.g. we somehow picked the wrong version).
logger.info("Failed to setup collector to record jemalloc stats: %s", e)
|
