-
Notifications
You must be signed in to change notification settings - Fork 3.9k
/
runqlat_example.txt
577 lines (488 loc) · 31.3 KB
/
runqlat_example.txt
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
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
Demonstrations of runqlat, the Linux eBPF/bcc version.
This program summarizes scheduler run queue latency as a histogram, showing
how long tasks spent waiting their turn to run on-CPU.
Here is a heavily loaded system:
# ./runqlat
Tracing run queue latency... Hit Ctrl-C to end.
^C
usecs : count distribution
0 -> 1 : 233 |*********** |
2 -> 3 : 742 |************************************ |
4 -> 7 : 203 |********** |
8 -> 15 : 173 |******** |
16 -> 31 : 24 |* |
32 -> 63 : 0 | |
64 -> 127 : 30 |* |
128 -> 255 : 6 | |
256 -> 511 : 3 | |
512 -> 1023 : 5 | |
1024 -> 2047 : 27 |* |
2048 -> 4095 : 30 |* |
4096 -> 8191 : 20 | |
8192 -> 16383 : 29 |* |
16384 -> 32767 : 809 |****************************************|
32768 -> 65535 : 64 |*** |
The distribution is bimodal, with one mode between 0 and 15 microseconds,
and another between 16 and 65 milliseconds. These modes are visible as the
spikes in the ASCII distribution (which is merely a visual representation
of the "count" column). As an example of reading one line: 809 events fell
into the 16384 to 32767 microsecond range (16 to 32 ms) while tracing.
I would expect the two modes to be due the workload: 16 hot CPU-bound threads,
and many other mostly idle threads doing occasional work. I suspect the mostly
idle threads will run with a higher priority when they wake up, and are
the reason for the low latency mode. The high latency mode will be the
CPU-bound threads. More analysis with this and other tools can confirm.
A -m option can be used to show milliseconds instead, as well as an interval
and a count. For example, showing three x five second summary in milliseconds:
# ./runqlat -m 5 3
Tracing run queue latency... Hit Ctrl-C to end.
msecs : count distribution
0 -> 1 : 3818 |****************************************|
2 -> 3 : 39 | |
4 -> 7 : 39 | |
8 -> 15 : 62 | |
16 -> 31 : 2214 |*********************** |
32 -> 63 : 226 |** |
msecs : count distribution
0 -> 1 : 3775 |****************************************|
2 -> 3 : 52 | |
4 -> 7 : 37 | |
8 -> 15 : 65 | |
16 -> 31 : 2230 |*********************** |
32 -> 63 : 212 |** |
msecs : count distribution
0 -> 1 : 3816 |****************************************|
2 -> 3 : 49 | |
4 -> 7 : 40 | |
8 -> 15 : 53 | |
16 -> 31 : 2228 |*********************** |
32 -> 63 : 221 |** |
This shows a similar distribution across the three summaries.
A -p option can be used to show one PID only, which is filtered in kernel for
efficiency. For example, PID 4505, and one second summaries:
# ./runqlat -mp 4505 1
Tracing run queue latency... Hit Ctrl-C to end.
msecs : count distribution
0 -> 1 : 1 |* |
2 -> 3 : 2 |*** |
4 -> 7 : 1 |* |
8 -> 15 : 0 | |
16 -> 31 : 25 |****************************************|
32 -> 63 : 3 |**** |
msecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 2 |** |
4 -> 7 : 0 | |
8 -> 15 : 1 |* |
16 -> 31 : 30 |****************************************|
32 -> 63 : 1 |* |
msecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 28 |****************************************|
32 -> 63 : 2 |** |
msecs : count distribution
0 -> 1 : 1 |* |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 27 |****************************************|
32 -> 63 : 4 |***** |
[...]
For comparison, here is pidstat(1) for that process:
# pidstat -p 4505 1
Linux 4.4.0-virtual (bgregg-xxxxxxxx) 02/08/2016 _x86_64_ (8 CPU)
08:56:11 AM UID PID %usr %system %guest %CPU CPU Command
08:56:12 AM 0 4505 9.00 3.00 0.00 12.00 0 bash
08:56:13 AM 0 4505 7.00 5.00 0.00 12.00 0 bash
08:56:14 AM 0 4505 10.00 2.00 0.00 12.00 0 bash
08:56:15 AM 0 4505 11.00 2.00 0.00 13.00 0 bash
08:56:16 AM 0 4505 9.00 3.00 0.00 12.00 0 bash
[...]
This is a synthetic workload that is CPU bound. It's only spending 12% on-CPU
each second because of high CPU demand on this server: the remaining time
is spent waiting on a run queue, as visualized by runqlat.
Here is the same system, but when it is CPU idle:
# ./runqlat 5 1
Tracing run queue latency... Hit Ctrl-C to end.
usecs : count distribution
0 -> 1 : 2250 |******************************** |
2 -> 3 : 2340 |********************************** |
4 -> 7 : 2746 |****************************************|
8 -> 15 : 418 |****** |
16 -> 31 : 93 |* |
32 -> 63 : 28 | |
64 -> 127 : 119 |* |
128 -> 255 : 9 | |
256 -> 511 : 4 | |
512 -> 1023 : 20 | |
1024 -> 2047 : 22 | |
2048 -> 4095 : 5 | |
4096 -> 8191 : 2 | |
Back to a microsecond scale, this time there is little run queue latency past 1
millisecond, as would be expected.
Now 16 threads are performing heavy disk I/O:
# ./runqlat 5 1
Tracing run queue latency... Hit Ctrl-C to end.
usecs : count distribution
0 -> 1 : 204 | |
2 -> 3 : 944 |* |
4 -> 7 : 16315 |********************* |
8 -> 15 : 29897 |****************************************|
16 -> 31 : 1044 |* |
32 -> 63 : 23 | |
64 -> 127 : 128 | |
128 -> 255 : 24 | |
256 -> 511 : 5 | |
512 -> 1023 : 13 | |
1024 -> 2047 : 15 | |
2048 -> 4095 : 13 | |
4096 -> 8191 : 10 | |
The distribution hasn't changed too much. While the disks are 100% busy, there
is still plenty of CPU headroom, and threads still don't spend much time
waiting their turn.
A -P option will print a distribution for each PID:
# ./runqlat -P
Tracing run queue latency... Hit Ctrl-C to end.
^C
pid = 0
usecs : count distribution
0 -> 1 : 351 |******************************** |
2 -> 3 : 96 |******** |
4 -> 7 : 437 |****************************************|
8 -> 15 : 12 |* |
16 -> 31 : 10 | |
32 -> 63 : 0 | |
64 -> 127 : 16 |* |
128 -> 255 : 0 | |
256 -> 511 : 0 | |
512 -> 1023 : 0 | |
1024 -> 2047 : 0 | |
2048 -> 4095 : 0 | |
4096 -> 8191 : 0 | |
8192 -> 16383 : 1 | |
pid = 12929
usecs : count distribution
0 -> 1 : 1 |****************************************|
2 -> 3 : 0 | |
4 -> 7 : 1 |****************************************|
pid = 12930
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 1 |****************************************|
32 -> 63 : 0 | |
64 -> 127 : 1 |****************************************|
pid = 12931
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 1 |******************** |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 0 | |
512 -> 1023 : 2 |****************************************|
pid = 12932
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 1 |****************************************|
256 -> 511 : 0 | |
512 -> 1023 : 1 |****************************************|
pid = 7
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 426 |************************************* |
4 -> 7 : 457 |****************************************|
8 -> 15 : 16 |* |
pid = 9
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 425 |****************************************|
8 -> 15 : 16 |* |
pid = 11
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 10 |****************************************|
pid = 14
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 8 |****************************************|
4 -> 7 : 2 |********** |
pid = 18
usecs : count distribution
0 -> 1 : 414 |****************************************|
2 -> 3 : 0 | |
4 -> 7 : 20 |* |
8 -> 15 : 8 | |
pid = 12928
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 1 |****************************************|
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 1 |****************************************|
pid = 1867
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 15 |****************************************|
16 -> 31 : 1 |** |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 4 |********** |
pid = 1871
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 2 |****************************************|
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 0 | |
512 -> 1023 : 1 |******************** |
pid = 1876
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 1 |****************************************|
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 1 |****************************************|
pid = 1878
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 3 |****************************************|
pid = 1880
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 3 |****************************************|
pid = 9307
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 1 |****************************************|
pid = 1886
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 1 |******************** |
8 -> 15 : 2 |****************************************|
pid = 1888
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 3 |****************************************|
pid = 3297
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 1 |****************************************|
pid = 1892
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 1 |******************** |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 0 | |
512 -> 1023 : 2 |****************************************|
pid = 7024
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 4 |****************************************|
pid = 16468
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 3 |****************************************|
pid = 12922
usecs : count distribution
0 -> 1 : 1 |****************************************|
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 1 |****************************************|
16 -> 31 : 1 |****************************************|
32 -> 63 : 0 | |
64 -> 127 : 1 |****************************************|
pid = 12923
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 1 |******************** |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 2 |****************************************|
128 -> 255 : 0 | |
256 -> 511 : 0 | |
512 -> 1023 : 1 |******************** |
1024 -> 2047 : 1 |******************** |
pid = 12924
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 2 |******************** |
8 -> 15 : 4 |****************************************|
16 -> 31 : 1 |********** |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 0 | |
512 -> 1023 : 0 | |
1024 -> 2047 : 1 |********** |
pid = 12925
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 1 |****************************************|
pid = 12926
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 1 |****************************************|
4 -> 7 : 0 | |
8 -> 15 : 1 |****************************************|
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 0 | |
512 -> 1023 : 1 |****************************************|
pid = 12927
usecs : count distribution
0 -> 1 : 1 |****************************************|
2 -> 3 : 0 | |
4 -> 7 : 1 |****************************************|
A -L option will print a distribution for each TID:
# ./runqlat -L
Tracing run queue latency... Hit Ctrl-C to end.
^C
tid = 0
usecs : count distribution
0 -> 1 : 593 |**************************** |
2 -> 3 : 829 |****************************************|
4 -> 7 : 300 |************** |
8 -> 15 : 321 |*************** |
16 -> 31 : 132 |****** |
32 -> 63 : 58 |** |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 13 | |
tid = 7
usecs : count distribution
0 -> 1 : 8 |******** |
2 -> 3 : 19 |******************** |
4 -> 7 : 37 |****************************************|
[...]
And a --pidnss option (short for PID namespaces) will print for each PID
namespace, for analyzing container performance:
# ./runqlat --pidnss -m
Tracing run queue latency... Hit Ctrl-C to end.
^C
pidns = 4026532870
msecs : count distribution
0 -> 1 : 40 |****************************************|
2 -> 3 : 1 |* |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 2 |** |
64 -> 127 : 5 |***** |
pidns = 4026532809
msecs : count distribution
0 -> 1 : 67 |****************************************|
pidns = 4026532748
msecs : count distribution
0 -> 1 : 63 |****************************************|
pidns = 4026532687
msecs : count distribution
0 -> 1 : 7 |****************************************|
pidns = 4026532626
msecs : count distribution
0 -> 1 : 45 |****************************************|
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 3 |** |
pidns = 4026531836
msecs : count distribution
0 -> 1 : 314 |****************************************|
2 -> 3 : 1 | |
4 -> 7 : 11 |* |
8 -> 15 : 28 |*** |
16 -> 31 : 137 |***************** |
32 -> 63 : 86 |********** |
64 -> 127 : 1 | |
pidns = 4026532382
msecs : count distribution
0 -> 1 : 285 |****************************************|
2 -> 3 : 5 | |
4 -> 7 : 16 |** |
8 -> 15 : 9 |* |
16 -> 31 : 69 |********* |
32 -> 63 : 25 |*** |
Many of these distributions have two modes: the second, in this case, is
caused by capping CPU usage via CPU shares.
USAGE message:
# ./runqlat -h
usage: runqlat.py [-h] [-T] [-m] [-P] [--pidnss] [-L] [-p PID]
[interval] [count]
Summarize run queue (scheduler) latency as a histogram
positional arguments:
interval output interval, in seconds
count number of outputs
optional arguments:
-h, --help show this help message and exit
-T, --timestamp include timestamp on output
-m, --milliseconds millisecond histogram
-P, --pids print a histogram per process ID
--pidnss print a histogram per PID namespace
-L, --tids print a histogram per thread ID
-p PID, --pid PID trace this PID only
examples:
./runqlat # summarize run queue latency as a histogram
./runqlat 1 10 # print 1 second summaries, 10 times
./runqlat -mT 1 # 1s summaries, milliseconds, and timestamps
./runqlat -P # show each PID separately
./runqlat -p 185 # trace PID 185 only