System power-management sysfs ABI | Linux 6.18.37

요약·해설과 원문, 전문 번역을 서로 분리했습니다. API 이름, symbol, source path는 원문 표기를 사용합니다.

1. 요약·해설

원문의 핵심 논리와 kernel programming 관점의 보충 설명입니다. 아래의 전문 번역과는 별도로 작성했습니다.

Sleep states와 suspend mode

sysfs-power:1-41

Unified /sys/power interface에서 freeze·standby·mem·disk state와 mem suspend의 s2idle·shallow·deep operating mode를 선택합니다.

Hibernation methods와 image

sysfs-power:42-107

Firmware·platform·shutdown·reboot 방식과 testproc·test diagnostic sequence, image-size upper limit를 제어합니다.

PM trace와 callback scheduling

sysfs-power:108-169

RTC hash로 suspend/resume hang을 추적하고 loadable-module devices를 대조하며 asynchronous callback 실행을 선택합니다.

Wakeup race, autosleep와 wake locks

sysfs-power:170-258

Wakeup count handshake로 race를 막고 active sources가 없을 때 autosleep을 반복하며 named wake locks를 timeout 또는 explicit unlock으로 관리합니다.

Timing, IRQ, debug와 resume offset

sysfs-power:259-309

Device PM duration, first wakeup IRQ, suspend/hibernation debug logging과 hibernation disk offset을 제공합니다.

Suspend failures와 hardware sleep time

sysfs-power:310-444

Suspend pipeline 단계별 success/failure counts, 마지막 실패 device·errno·step과 microsecond hardware-sleep durations를 기록합니다.

Suspend 전 filesystem sync

sysfs-power:445-456

User space freeze와 device suspend 사이의 sync() 실행 여부를 runtime value와 build-time default로 제어합니다.

2. 영어 원문 전체

번역 기준이 된 Linux v6.18.37 원문입니다. 줄 번호는 이 버전의 파일 좌표입니다.

원문 전체 펼치기

1 What: /sys/power/

2 Date: August 2006

3 Contact: Rafael J. Wysocki <[email protected]>

4 Description:

5 The /sys/power directory will contain files that will

6 provide a unified interface to the power management

7 subsystem.

9 What: /sys/power/state

10 Date: November 2016

11 Contact: Rafael J. Wysocki <[email protected]>

12 Description:

13 The /sys/power/state file controls system sleep states.

14 Reading from this file returns the available sleep state

15 labels, which may be "mem" (suspend), "standby" (power-on

16 suspend), "freeze" (suspend-to-idle) and "disk" (hibernation).

18 Writing one of the above strings to this file causes the system

19 to transition into the corresponding state, if available.

21 See Documentation/admin-guide/pm/sleep-states.rst for more

22 information.

24 What: /sys/power/mem_sleep

25 Date: November 2016

26 Contact: Rafael J. Wysocki <[email protected]>

27 Description:

28 The /sys/power/mem_sleep file controls the operating mode of

29 system suspend. Reading from it returns the available modes

30 as "s2idle" (always present), "shallow" and "deep" (present if

31 supported). The mode that will be used on subsequent attempts

32 to suspend the system (by writing "mem" to the /sys/power/state

33 file described above) is enclosed in square brackets.

35 Writing one of the above strings to this file causes the mode

36 represented by it to be used on subsequent attempts to suspend

37 the system.

39 See Documentation/admin-guide/pm/sleep-states.rst for more

40 information.

42 What: /sys/power/disk

43 Date: September 2006

44 Contact: Rafael J. Wysocki <[email protected]>

45 Description:

46 The /sys/power/disk file controls the operating mode of the

47 suspend-to-disk mechanism. Reading from this file returns

48 the name of the method by which the system will be put to

49 sleep on the next suspend. There are four methods supported:

51 'firmware' - means that the memory image will be saved to disk

52 by some firmware, in which case we also assume that the

53 firmware will handle the system suspend.

55 'platform' - the memory image will be saved by the kernel and

56 the system will be put to sleep by the platform driver (e.g.

57 ACPI or other PM registers).

59 'shutdown' - the memory image will be saved by the kernel and

60 the system will be powered off.

62 'reboot' - the memory image will be saved by the kernel and

63 the system will be rebooted.

65 Additionally, /sys/power/disk can be used to turn on one of the

66 two testing modes of the suspend-to-disk mechanism: 'testproc'

67 or 'test'. If the suspend-to-disk mechanism is in the

68 'testproc' mode, writing 'disk' to /sys/power/state will cause

69 the kernel to disable nonboot CPUs and freeze tasks, wait for 5

70 seconds, unfreeze tasks and enable nonboot CPUs. If it is in

71 the 'test' mode, writing 'disk' to /sys/power/state will cause

72 the kernel to disable nonboot CPUs and freeze tasks, shrink

73 memory, suspend devices, wait for 5 seconds, resume devices,

74 unfreeze tasks and enable nonboot CPUs. Then, we are able to

75 look in the log messages and work out, for example, which code

76 is being slow and which device drivers are misbehaving.

78 The suspend-to-disk method may be chosen by writing to this

79 file one of the accepted strings:

81 - 'firmware'

82 - 'platform'

83 - 'shutdown'

84 - 'reboot'

85 - 'testproc'

86 - 'test'

88 It will only change to 'firmware' or 'platform' if the system

89 supports that.

91 What: /sys/power/image_size

92 Date: August 2006

93 Contact: Rafael J. Wysocki <[email protected]>

94 Description:

95 The /sys/power/image_size file controls the size of the image

96 created by the suspend-to-disk mechanism. It can be written a

97 string representing a non-negative integer that will be used

98 as an upper limit of the image size, in bytes. The kernel's

99 suspend-to-disk code will do its best to ensure the image size

100 will not exceed this number. However, if it turns out to be

101 impossible, the kernel will try to suspend anyway using the

102 smallest image possible. In particular, if "0" is written to

103 this file, the suspend image will be as small as possible.

104

105 Reading from this file will display the current image size

106 limit, which is set to around 2/5 of available RAM by default.

107

108 What: /sys/power/pm_trace

109 Date: August 2006

110 Contact: Rafael J. Wysocki <[email protected]>

111 Description:

112 The /sys/power/pm_trace file controls the code which saves the

113 last PM event point in the RTC across reboots, so that you can

114 debug a machine that just hangs during suspend (or more

115 commonly, during resume). Namely, the RTC is only used to save

116 the last PM event point if this file contains '1'. Initially

117 it contains '0' which may be changed to '1' by writing a

118 string representing a nonzero integer into it.

119

120 To use this debugging feature you should attempt to suspend

121 the machine, then reboot it and run::

122

123 dmesg -s 1000000 | grep 'hash matches'

124

125 If you do not get any matches (or they appear to be false

126 positives), it is possible that the last PM event point

127 referred to a device created by a loadable kernel module. In

128 this case cat /sys/power/pm_trace_dev_match (see below) after

129 your system is started up and the kernel modules are loaded.

130

131 CAUTION: Using it will cause your machine's real-time (CMOS)

132 clock to be set to a random invalid time after a resume.

133

134 What: /sys/power/pm_trace_dev_match

135 Date: October 2010

136 Contact: James Hogan <[email protected]>

137 Description:

138 The /sys/power/pm_trace_dev_match file contains the name of the

139 device associated with the last PM event point saved in the RTC

140 across reboots when pm_trace has been used. More precisely it

141 contains the list of current devices (including those

142 registered by loadable kernel modules since boot) which match

143 the device hash in the RTC at boot, with a newline after each

144 one.

145

146 The advantage of this file over the hash matches printed to the

147 kernel log (see /sys/power/pm_trace), is that it includes

148 devices created after boot by loadable kernel modules.

149

150 Due to the small hash size necessary to fit in the RTC, it is

151 possible that more than one device matches the hash, in which

152 case further investigation is required to determine which

153 device is causing the problem. Note that genuine RTC clock

154 values (such as when pm_trace has not been used), can still

155 match a device and output its name here.

156

157 What: /sys/power/pm_async

158 Date: January 2009

159 Contact: Rafael J. Wysocki <[email protected]>

160 Description:

161 The /sys/power/pm_async file controls the switch allowing the

162 user space to enable or disable asynchronous suspend and resume

163 of devices. If enabled, this feature will cause some device

164 drivers' suspend and resume callbacks to be executed in parallel

165 with each other and with the main suspend thread. It is enabled

166 if this file contains "1", which is the default. It may be

167 disabled by writing "0" to this file, in which case all devices

168 will be suspended and resumed synchronously.

169

170 What: /sys/power/wakeup_count

171 Date: July 2010

172 Contact: Rafael J. Wysocki <[email protected]>

173 Description:

174 The /sys/power/wakeup_count file allows user space to put the

175 system into a sleep state while taking into account the

176 concurrent arrival of wakeup events. Reading from it returns

177 the current number of registered wakeup events and it blocks if

178 some wakeup events are being processed at the time the file is

179 read from. Writing to it will only succeed if the current

180 number of wakeup events is equal to the written value and, if

181 successful, will make the kernel abort a subsequent transition

182 to a sleep state if any wakeup events are reported after the

183 write has returned.

184

185 What: /sys/power/reserved_size

186 Date: May 2011

187 Contact: Rafael J. Wysocki <[email protected]>

188 Description:

189 The /sys/power/reserved_size file allows user space to control

190 the amount of memory reserved for allocations made by device

191 drivers during the "device freeze" stage of hibernation. It can

192 be written a string representing a non-negative integer that

193 will be used as the amount of memory to reserve for allocations

194 made by device drivers' "freeze" callbacks, in bytes.

195

196 Reading from this file will display the current value, which is

197 set to 1 MB by default.

198

199 What: /sys/power/autosleep

200 Date: April 2012

201 Contact: Rafael J. Wysocki <[email protected]>

202 Description:

203 The /sys/power/autosleep file can be written one of the strings

204 returned by reads from /sys/power/state. If that happens, a

205 work item attempting to trigger a transition of the system to

206 the sleep state represented by that string is queued up. This

207 attempt will only succeed if there are no active wakeup sources

208 in the system at that time. After every execution, regardless

209 of whether or not the attempt to put the system to sleep has

210 succeeded, the work item requeues itself until user space

211 writes "off" to /sys/power/autosleep.

212

213 Reading from this file causes the last string successfully

214 written to it to be returned.

215

216 What: /sys/power/wake_lock

217 Date: February 2012

218 Contact: Rafael J. Wysocki <[email protected]>

219 Description:

220 The /sys/power/wake_lock file allows user space to create

221 wakeup source objects and activate them on demand (if one of

222 those wakeup sources is active, reads from the

223 /sys/power/wakeup_count file block or return false). When a

224 string without white space is written to /sys/power/wake_lock,

225 it will be assumed to represent a wakeup source name. If there

226 is a wakeup source object with that name, it will be activated

227 (unless active already). Otherwise, a new wakeup source object

228 will be registered, assigned the given name and activated.

229 If a string written to /sys/power/wake_lock contains white

230 space, the part of the string preceding the white space will be

231 regarded as a wakeup source name and handled as descrived above.

232 The other part of the string will be regarded as a timeout (in

233 nanoseconds) such that the wakeup source will be automatically

234 deactivated after it has expired. The timeout, if present, is

235 set regardless of the current state of the wakeup source object

236 in question.

237

238 Reads from this file return a string consisting of the names of

239 wakeup sources created with the help of it that are active at

240 the moment, separated with spaces.

241

242

243 What: /sys/power/wake_unlock

244 Date: February 2012

245 Contact: Rafael J. Wysocki <[email protected]>

246 Description:

247 The /sys/power/wake_unlock file allows user space to deactivate

248 wakeup sources created with the help of /sys/power/wake_lock.

249 When a string is written to /sys/power/wake_unlock, it will be

250 assumed to represent the name of a wakeup source to deactivate.

251

252 If a wakeup source object of that name exists and is active at

253 the moment, it will be deactivated.

254

255 Reads from this file return a string consisting of the names of

256 wakeup sources created with the help of /sys/power/wake_lock

257 that are inactive at the moment, separated with spaces.

258

259 What: /sys/power/pm_print_times

260 Date: May 2012

261 Contact: Sameer Nanda <[email protected]>

262 Description:

263 The /sys/power/pm_print_times file allows user space to

264 control whether the time taken by devices to suspend and

265 resume is printed. These prints are useful for hunting down

266 devices that take too long to suspend or resume.

267

268 Writing a "1" enables this printing while writing a "0"

269 disables it. The default value is "0". Reading from this file

270 will display the current value.

271

272 What: /sys/power/pm_wakeup_irq

273 Date: April 2015

274 Contact: Alexandra Yates <[email protected]>

275 Description:

276 The /sys/power/pm_wakeup_irq file reports to user space the IRQ

277 number of the first wakeup interrupt (that is, the first

278 interrupt from an IRQ line armed for system wakeup) seen by the

279 kernel during the most recent system suspend/resume cycle.

280

281 This output is useful for system wakeup diagnostics of spurious

282 wakeup interrupts.

283

284 What: /sys/power/pm_debug_messages

285 Date: July 2017

286 Contact: Rafael J. Wysocki <[email protected]>

287 Description:

288 The /sys/power/pm_debug_messages file controls the printing

289 of debug messages from the system suspend/hiberbation

290 infrastructure to the kernel log.

291

292 Writing a "1" to this file enables the debug messages and

293 writing a "0" (default) to it disables them. Reads from

294 this file return the current value.

295

296 What: /sys/power/resume_offset

297 Date: April 2018

298 Contact: Mario Limonciello <[email protected]>

299 Description:

300 This file is used for telling the kernel an offset into a disk

301 to use when hibernating the system such as with a swap file.

302

303 Reads from this file will display the current offset

304 the kernel will be using on the next hibernation

305 attempt.

306

307 Using this sysfs file will override any values that were

308 set using the kernel command line for disk offset.

309

310 What: /sys/power/suspend_stats

311 Date: July 2019

312 Contact: Kalesh Singh <[email protected]>

313 Description:

314 The /sys/power/suspend_stats directory contains suspend related

315 statistics.

316

317 What: /sys/power/suspend_stats/success

318 Date: July 2019

319 Contact: Kalesh Singh <[email protected]>

320 Description:

321 The /sys/power/suspend_stats/success file contains the number

322 of times entering system sleep state succeeded.

323

324 What: /sys/power/suspend_stats/fail

325 Date: July 2019

326 Contact: Kalesh Singh <[email protected]>

327 Description:

328 The /sys/power/suspend_stats/fail file contains the number

329 of times entering system sleep state failed.

330

331 What: /sys/power/suspend_stats/failed_freeze

332 Date: July 2019

333 Contact: Kalesh Singh <[email protected]>

334 Description:

335 The /sys/power/suspend_stats/failed_freeze file contains the

336 number of times freezing processes failed.

337

338 What: /sys/power/suspend_stats/failed_prepare

339 Date: July 2019

340 Contact: Kalesh Singh <[email protected]>

341 Description:

342 The /sys/power/suspend_stats/failed_prepare file contains the

343 number of times preparing all non-sysdev devices for

344 a system PM transition failed.

345

346 What: /sys/power/suspend_stats/failed_resume

347 Date: July 2019

348 Contact: Kalesh Singh <[email protected]>

349 Description:

350 The /sys/power/suspend_stats/failed_resume file contains the

351 number of times executing "resume" callbacks of

352 non-sysdev devices failed.

353

354 What: /sys/power/suspend_stats/failed_resume_early

355 Date: July 2019

356 Contact: Kalesh Singh <[email protected]>

357 Description:

358 The /sys/power/suspend_stats/failed_resume_early file contains

359 the number of times executing "early resume" callbacks

360 of devices failed.

361

362 What: /sys/power/suspend_stats/failed_resume_noirq

363 Date: July 2019

364 Contact: Kalesh Singh <[email protected]>

365 Description:

366 The /sys/power/suspend_stats/failed_resume_noirq file contains

367 the number of times executing "noirq resume" callbacks

368 of devices failed.

369

370 What: /sys/power/suspend_stats/failed_suspend

371 Date: July 2019

372 Contact: Kalesh Singh <[email protected]>

373 Description:

374 The /sys/power/suspend_stats/failed_suspend file contains

375 the number of times executing "suspend" callbacks

376 of all non-sysdev devices failed.

377

378 What: /sys/power/suspend_stats/failed_suspend_late

379 Date: July 2019

380 Contact: Kalesh Singh <[email protected]>

381 Description:

382 The /sys/power/suspend_stats/failed_suspend_late file contains

383 the number of times executing "late suspend" callbacks

384 of all devices failed.

385

386 What: /sys/power/suspend_stats/failed_suspend_noirq

387 Date: July 2019

388 Contact: Kalesh Singh <[email protected]>

389 Description:

390 The /sys/power/suspend_stats/failed_suspend_noirq file contains

391 the number of times executing "noirq suspend" callbacks

392 of all devices failed.

393

394 What: /sys/power/suspend_stats/last_failed_dev

395 Date: July 2019

396 Contact: Kalesh Singh <[email protected]>

397 Description:

398 The /sys/power/suspend_stats/last_failed_dev file contains

399 the last device for which a suspend/resume callback failed.

400

401 What: /sys/power/suspend_stats/last_failed_errno

402 Date: July 2019

403 Contact: Kalesh Singh <[email protected]>

404 Description:

405 The /sys/power/suspend_stats/last_failed_errno file contains

406 the errno of the last failed attempt at entering

407 system sleep state.

408

409 What: /sys/power/suspend_stats/last_failed_step

410 Date: July 2019

411 Contact: Kalesh Singh <[email protected]>

412 Description:

413 The /sys/power/suspend_stats/last_failed_step file contains

414 the last failed step in the suspend/resume path.

415

416 What: /sys/power/suspend_stats/last_hw_sleep

417 Date: June 2023

418 Contact: Mario Limonciello <[email protected]>

419 Description:

420 The /sys/power/suspend_stats/last_hw_sleep file

421 contains the duration of time spent in a hardware sleep

422 state in the most recent system suspend-resume cycle.

423 This number is measured in microseconds.

424

425 What: /sys/power/suspend_stats/total_hw_sleep

426 Date: June 2023

427 Contact: Mario Limonciello <[email protected]>

428 Description:

429 The /sys/power/suspend_stats/total_hw_sleep file

430 contains the aggregate of time spent in a hardware sleep

431 state since the kernel was booted. This number

432 is measured in microseconds.

433

434 What: /sys/power/suspend_stats/max_hw_sleep

435 Date: June 2023

436 Contact: Mario Limonciello <[email protected]>

437 Description:

438 The /sys/power/suspend_stats/max_hw_sleep file

439 contains the maximum amount of time that the hardware can

440 report for time spent in a hardware sleep state. When sleep

441 cycles are longer than this time, the values for

442 'total_hw_sleep' and 'last_hw_sleep' may not be accurate.

443 This number is measured in microseconds.

444

445 What: /sys/power/sync_on_suspend

446 Date: October 2019

447 Contact: Jonas Meurer <[email protected]>

448 Description:

449 This file controls whether or not the kernel will sync()

450 filesystems during system suspend (after freezing user space

451 and before suspending devices).

452

453 Writing a "1" to this file enables the sync() and writing a "0"

454 disables it. Reads from the file return the current value.

455 The default is "1" if the build-time "SUSPEND_SKIP_SYNC" config

456 flag is unset, or "0" otherwise.

457

3. 한국어 전문 번역

영어 원문의 문단 순서와 의미를 유지한 전체 번역입니다. 코드, 함수명, symbol과 URL은 원문 표기를 유지합니다.

System power sysfs ABI: power management root

1-8

항목	한국어 전문 번역
What	/sys/power/
Date	2006년 8월
KernelVersion
Contact	Rafael J. Wysocki <[email protected]>
Description	`/sys/power/` directory에는 power-management subsystem에 대한 unified interface를 제공하는 files가 들어 있습니다.

System power sysfs ABI: state

9-23

항목	한국어 전문 번역
What	/sys/power/state
Date	2016년 11월
KernelVersion
Contact	Rafael J. Wysocki <[email protected]>
Description	`/sys/power/state`는 system sleep states를 제어합니다. Read하면 available sleep-state labels를 반환하며 `mem`은 suspend, `standby`는 power-on suspend, `freeze`는 suspend-to-idle, `disk`는 hibernation입니다. Available label 하나를 쓰면 system이 대응 state로 transition합니다. 자세한 내용은 `Documentation/admin-guide/pm/sleep-states.rst`를 참조합니다.

System sleep-state labels

LabelSleep state

freezeSuspend-to-idle

standbyPower-on suspend

memSuspend using selected mem_sleep mode

diskHibernation

state file의 read labels와 corresponding transitions입니다.

System power sysfs ABI: mem sleep

24-41

항목	한국어 전문 번역
What	/sys/power/mem_sleep
Date	2016년 11월
KernelVersion
Contact	Rafael J. Wysocki <[email protected]>
Description	`/sys/power/mem_sleep`은 system suspend의 operating mode를 제어합니다. Read하면 항상 존재하는 `s2idle`과 지원되는 경우의 `shallow`, `deep`을 반환합니다. 이후 `/sys/power/state`에 `mem`을 쓸 때 사용할 mode는 square brackets로 둘러싸여 표시됩니다. Mode string 하나를 쓰면 이후 suspend attempts에 그 mode를 사용합니다. 자세한 내용은 `Documentation/admin-guide/pm/sleep-states.rst`를 참조합니다.

mem_sleep suspend modes

ModeAvailabilityMeaning

s2idleAlways presentSuspend-to-idle

shallowIf supportedShallow system suspend

deepIf supportedDeep system suspend

Available modes와 availability를 정리합니다. Selected mode는 read output에서 square brackets로 표시됩니다.

Selecting the mem suspend mode

Write s2idle, shallow or deepSelected mode appears in [brackets]Write mem to /sys/power/stateSuspend in selected mode

mem_sleep selection은 다음 state=mem transition에 적용됩니다.

System power sysfs ABI: disk

42-90

항목	한국어 전문 번역
What	/sys/power/disk
Date	2006년 9월
KernelVersion
Contact	Rafael J. Wysocki <[email protected]>
Description	`/sys/power/disk`는 suspend-to-disk mechanism의 operating mode를 제어합니다. `firmware`는 firmware가 memory image를 disk에 저장하고 system suspend도 처리함을 뜻합니다. `platform`은 kernel이 image를 저장하고 ACPI 또는 다른 PM registers 같은 platform driver가 system을 sleep 상태로 만듭니다. `shutdown`은 kernel이 image를 저장한 뒤 power off하고, `reboot`는 image를 저장한 뒤 reboot합니다. Test mode `testproc`에서 `/sys/power/state`에 `disk`를 쓰면 nonboot CPUs를 disable하고 tasks를 freeze한 뒤 5 seconds를 기다렸다가 tasks를 unfreeze하고 CPUs를 enable합니다. `test` mode는 그 사이에 memory shrink, device suspend, 5-second wait와 device resume까지 수행합니다. Logs로 느린 code와 오동작하는 drivers를 찾을 수 있습니다. Accepted strings는 `firmware`, `platform`, `shutdown`, `reboot`, `testproc`, `test`이며 `firmware`와 `platform`은 system이 지원할 때만 선택됩니다.

Suspend-to-disk methods

MethodImage saved byFinal action

firmwareFirmwareFirmware handles suspend

platformKernelPlatform driver puts system to sleep

shutdownKernelPower off

rebootKernelReboot

Memory image writer와 final platform action을 구분합니다.

Suspend-to-disk test modes

ModeSequence

testprocDisable nonboot CPUs; freeze tasks; wait 5s; unfreeze; enable CPUs

testDisable CPUs; freeze; shrink memory; suspend devices; wait 5s; resume; unfreeze; enable CPUs

두 test modes가 실행하는 단계와 5-second wait를 비교합니다.

System power sysfs ABI: image size

91-107

항목	한국어 전문 번역
What	/sys/power/image_size
Date	2006년 8월
KernelVersion
Contact	Rafael J. Wysocki <[email protected]>
Description	`/sys/power/image_size`는 suspend-to-disk image size를 제어합니다. Non-negative integer string을 쓰면 bytes 단위 upper limit로 사용하며 kernel은 image가 이를 넘지 않도록 최선을 다합니다. 불가능하면 가능한 가장 작은 image로 suspend를 계속 시도합니다. `0`을 쓰면 image를 가능한 한 작게 만듭니다. Read하면 current limit를 표시하며 default는 available RAM의 약 `2/5`입니다.

Hibernation image-size behavior

Input or stateBehavior

Non-negative integerUpper limit in bytes

0Make image as small as possible

DefaultAround 2/5 of available RAM

Limit impossibleTry suspend with smallest possible image

Requested upper limit, zero special case와 default를 정리합니다.

System power sysfs ABI: pm trace

108-133

항목	한국어 전문 번역
What	/sys/power/pm_trace
Date	2006년 8월
KernelVersion
Contact	Rafael J. Wysocki <[email protected]>
Description	`/sys/power/pm_trace`는 마지막 PM event point를 reboot 사이에도 RTC에 저장하여 suspend 또는 resume 중 hang을 debug하게 합니다. File이 `1`일 때만 RTC를 사용하며 initial value는 `0`입니다. Nonzero integer string을 쓰면 enable됩니다. Suspend를 시도하고 reboot한 뒤 `dmesg -s 1000000 \| grep 'hash matches'`를 실행합니다. Match가 없거나 false positive로 보이면 loadable kernel module이 만든 device일 수 있으므로 modules load 뒤 `/sys/power/pm_trace_dev_match`를 읽습니다. 주의: 이 기능을 사용하면 resume 뒤 real-time CMOS clock이 random invalid time으로 설정됩니다.

PM trace debugging

Write nonzero to pm_traceAttempt suspendHang or resume failureRebootSearch hash matches

No reliable matchLoad kernel modulesRead pm_trace_dev_matchInvestigate matching devices

RTC hash를 reboot 뒤 kernel log 또는 module-aware device list와 대조합니다.

dmesg -s 1000000 | grep 'hash matches'
cat /sys/power/pm_trace_dev_match

CAUTION: pm_trace 사용 뒤 resume하면 real-time CMOS clock이 random invalid time으로 바뀝니다.

System power sysfs ABI: pm trace dev match

134-156

항목	한국어 전문 번역
What	/sys/power/pm_trace_dev_match
Date	2010년 10월
KernelVersion
Contact	James Hogan <[email protected]>
Description	`/sys/power/pm_trace_dev_match`는 `pm_trace`가 사용됐을 때 reboot 사이 RTC에 저장된 마지막 PM event point와 연결된 device names를 담습니다. Boot 시 RTC device hash와 match하는 current devices를, boot 뒤 loadable kernel modules가 register한 devices까지 포함해 한 줄에 하나씩 나열합니다. RTC에 맞추기 위한 hash가 작아 둘 이상의 device가 match할 수 있으므로 원인 device를 추가 조사해야 합니다. `pm_trace`를 사용하지 않은 genuine RTC clock value도 우연히 device와 match할 수 있습니다.

System power sysfs ABI: pm async

157-169

항목	한국어 전문 번역
What	/sys/power/pm_async
Date	2009년 1월
KernelVersion
Contact	Rafael J. Wysocki <[email protected]>
Description	`/sys/power/pm_async`는 userspace가 asynchronous device suspend/resume을 enable 또는 disable하게 합니다. Enable하면 일부 driver callbacks가 서로 및 main suspend thread와 parallel로 실행됩니다. Default `1`은 enabled이고 `0`을 쓰면 모든 devices를 synchronously suspend/resume합니다.

Device PM callback scheduling

ValueCallback execution

1 (default)Eligible callbacks run asynchronously in parallel

0All devices suspend and resume synchronously

pm_async가 suspend/resume callbacks의 scheduling model을 선택합니다.

System power sysfs ABI: wakeup count

170-184

항목	한국어 전문 번역
What	/sys/power/wakeup_count
Date	2010년 7월
KernelVersion
Contact	Rafael J. Wysocki <[email protected]>
Description	`/sys/power/wakeup_count`는 concurrent wakeup events를 고려하면서 userspace가 system을 sleep state로 전환하게 합니다. Read하면 registered wakeup events의 current count를 반환하며 event 처리 중이면 block합니다. Write는 current count가 쓴 value와 같을 때만 성공합니다. 성공한 write 뒤 새 wakeup event가 보고되면 kernel이 subsequent sleep transition을 abort합니다.

Race-free wakeup-count handshake

Read wakeup_countWait for in-flight eventsWrite same countNo new eventAllow sleep transition

Write countNew wakeup event arrivesAbort subsequent sleep transition

Read와 matching write 사이에 wakeup activity가 생기면 sleep transition을 막습니다.

System power sysfs ABI: reserved size

185-198

항목	한국어 전문 번역
What	/sys/power/reserved_size
Date	2011년 5월
KernelVersion
Contact	Rafael J. Wysocki <[email protected]>
Description	`/sys/power/reserved_size`는 hibernation의 "device freeze" stage에서 device-driver `freeze` callbacks가 allocation할 수 있도록 reserve할 memory를 제어합니다. Non-negative integer string을 bytes 단위 reserve amount로 씁니다. Read하면 current value를 표시하며 default는 `1 MB`입니다.

System power sysfs ABI: autosleep

199-215

항목	한국어 전문 번역
What	/sys/power/autosleep
Date	2012년 4월
KernelVersion
Contact	Rafael J. Wysocki <[email protected]>
Description	`/sys/power/autosleep`에는 `/sys/power/state` read가 반환한 strings 중 하나를 쓸 수 있습니다. 그러면 해당 sleep state로 transition을 시도하는 work item이 queue됩니다. Active wakeup sources가 없을 때만 성공합니다. 성공 여부와 관계없이 실행할 때마다 userspace가 `off`를 쓸 때까지 work item이 자신을 다시 queue합니다. Read하면 마지막으로 성공적으로 쓴 string을 반환합니다.

Autosleep work loop

Write sleep-state labelQueue work itemCheck active wakeup sourcesAttempt sleep if noneRequeue work item

Write offStop autosleep loop

Active wakeup sources가 없을 때 sleep을 시도하고 off가 올 때까지 계속 requeue합니다.

System power sysfs ABI: wake lock

216-242

항목	한국어 전문 번역
What	/sys/power/wake_lock
Date	2012년 2월
KernelVersion
Contact	Rafael J. Wysocki <[email protected]>
Description	`/sys/power/wake_lock`은 userspace가 wakeup-source objects를 만들고 필요할 때 activate하게 합니다. Active source가 있으면 `/sys/power/wakeup_count` read가 block하거나 false를 반환합니다. Whitespace 없는 string은 source name입니다. 같은 name의 object가 있으면 activate하고, 없으면 새 object를 register·name·activate합니다. Whitespace가 있으면 앞부분은 name, 뒷부분은 nanoseconds 단위 timeout이며 timeout은 object current state와 관계없이 설정됩니다. Timeout이 expire하면 source가 자동 deactivate됩니다. Read하면 이 interface로 만들어졌고 현재 active인 source names를 spaces로 구분해 반환합니다.

wake_lock write syntax

InputEffect

nameCreate if needed and activate source

name timeout_nsActivate and set auto-deactivation timeout

Name-only activation과 optional nanosecond timeout을 구분합니다.

Wake-source lifecycle

Write name to wake_lockFind or register sourceActivateListed by wake_lock read

Timeout expires or write name to wake_unlockDeactivateListed by wake_unlock read

wake_lock은 create/activate하고 wake_unlock 또는 timeout은 deactivate합니다.

System power sysfs ABI: wake unlock

243-258

항목	한국어 전문 번역
What	/sys/power/wake_unlock
Date	2012년 2월
KernelVersion
Contact	Rafael J. Wysocki <[email protected]>
Description	`/sys/power/wake_unlock`은 `/sys/power/wake_lock`으로 만든 wakeup sources를 deactivate하게 합니다. 쓴 string을 deactivate할 source name으로 사용하며 해당 object가 존재하고 active이면 deactivate합니다. Read하면 이 interface로 만들어졌고 현재 inactive인 source names를 spaces로 구분해 반환합니다.

System power sysfs ABI: pm print times

259-271

항목	한국어 전문 번역
What	/sys/power/pm_print_times
Date	2012년 5월
KernelVersion
Contact	Sameer Nanda <[email protected]>
Description	`/sys/power/pm_print_times`는 device suspend/resume에 걸린 시간을 print할지 제어합니다. 느린 device를 찾는 데 유용합니다. `1`은 printing enable, `0`은 disable이며 default는 `0`입니다. Read하면 current value를 표시합니다.

Power-management diagnostic toggles

Attribute10Default

pm_print_timesPrint device PM timesDo not print0

pm_debug_messagesEnable debug messagesDisable0

sync_on_suspendRun sync()Skip sync()1 unless SUSPEND_SKIP_SYNC is set

Timing, debug logging과 filesystem sync controls의 enable values입니다.

System power sysfs ABI: pm wakeup irq

272-283

항목	한국어 전문 번역
What	/sys/power/pm_wakeup_irq
Date	2015년 4월
KernelVersion
Contact	Alexandra Yates <[email protected]>
Description	`/sys/power/pm_wakeup_irq`는 가장 최근 system suspend/resume cycle에서 kernel이 본 첫 wakeup interrupt, 즉 system wakeup용으로 armed된 IRQ line의 첫 interrupt 번호를 userspace에 보고합니다. Spurious wakeup interrupt 진단에 유용합니다.

System power sysfs ABI: pm debug messages

284-295

항목	한국어 전문 번역
What	/sys/power/pm_debug_messages
Date	2017년 7월
KernelVersion
Contact	Rafael J. Wysocki <[email protected]>
Description	`/sys/power/pm_debug_messages`는 system suspend/hibernation infrastructure의 debug messages를 kernel log에 print할지 제어합니다. `1`은 enable, default `0`은 disable이며 read하면 current value를 반환합니다.

System power sysfs ABI: resume offset

296-309

항목	한국어 전문 번역
What	/sys/power/resume_offset
Date	2018년 4월
KernelVersion
Contact	Mario Limonciello <[email protected]>
Description	`/sys/power/resume_offset`은 swap file 같은 disk를 사용해 hibernate할 때 kernel이 사용할 disk offset을 지정합니다. Read하면 다음 hibernation attempt에 사용할 current offset을 표시합니다. 이 sysfs file을 사용하면 disk offset에 대해 kernel command line으로 설정한 value를 override합니다.

System power sysfs ABI: suspend stats

310-316

항목	한국어 전문 번역
What	/sys/power/suspend_stats
Date	2019년 7월
KernelVersion
Contact	Kalesh Singh <[email protected]>
Description	`/sys/power/suspend_stats` directory에는 suspend-related statistics가 들어 있습니다.

Suspend failure counters and records

GroupAttributes

Outcomesuccess, fail

Freeze/preparefailed_freeze, failed_prepare

Suspend callbacksfailed_suspend, failed_suspend_late, failed_suspend_noirq

Resume callbacksfailed_resume_noirq, failed_resume_early, failed_resume

Last failurelast_failed_dev, last_failed_errno, last_failed_step

Suspend/resume pipeline의 failure phase와 last-failure records를 묶었습니다.

System power sysfs ABI: success

317-323

항목	한국어 전문 번역
What	/sys/power/suspend_stats/success
Date	2019년 7월
KernelVersion
Contact	Kalesh Singh <[email protected]>
Description	`/sys/power/suspend_stats/success`는 system sleep state 진입에 성공한 횟수입니다.

System power sysfs ABI: fail

324-330

항목	한국어 전문 번역
What	/sys/power/suspend_stats/fail
Date	2019년 7월
KernelVersion
Contact	Kalesh Singh <[email protected]>
Description	`/sys/power/suspend_stats/fail`은 system sleep state 진입에 실패한 횟수입니다.

System power sysfs ABI: failed freeze

331-337

항목	한국어 전문 번역
What	/sys/power/suspend_stats/failed_freeze
Date	2019년 7월
KernelVersion
Contact	Kalesh Singh <[email protected]>
Description	`/sys/power/suspend_stats/failed_freeze`는 process freezing이 실패한 횟수입니다.

System power sysfs ABI: failed prepare

338-345

항목	한국어 전문 번역
What	/sys/power/suspend_stats/failed_prepare
Date	2019년 7월
KernelVersion
Contact	Kalesh Singh <[email protected]>
Description	`/sys/power/suspend_stats/failed_prepare`는 system PM transition을 위해 모든 non-sysdev devices를 prepare하는 데 실패한 횟수입니다.

System power sysfs ABI: failed resume

346-353

항목	한국어 전문 번역
What	/sys/power/suspend_stats/failed_resume
Date	2019년 7월
KernelVersion
Contact	Kalesh Singh <[email protected]>
Description	`/sys/power/suspend_stats/failed_resume`은 non-sysdev devices의 `resume` callbacks 실행이 실패한 횟수입니다.

System power sysfs ABI: failed resume early

354-361

항목	한국어 전문 번역
What	/sys/power/suspend_stats/failed_resume_early
Date	2019년 7월
KernelVersion
Contact	Kalesh Singh <[email protected]>
Description	`/sys/power/suspend_stats/failed_resume_early`는 device `early resume` callbacks 실행이 실패한 횟수입니다.

System power sysfs ABI: failed resume noirq

362-369

항목	한국어 전문 번역
What	/sys/power/suspend_stats/failed_resume_noirq
Date	2019년 7월
KernelVersion
Contact	Kalesh Singh <[email protected]>
Description	`/sys/power/suspend_stats/failed_resume_noirq`는 device `noirq resume` callbacks 실행이 실패한 횟수입니다.

System power sysfs ABI: failed suspend

370-377

항목	한국어 전문 번역
What	/sys/power/suspend_stats/failed_suspend
Date	2019년 7월
KernelVersion
Contact	Kalesh Singh <[email protected]>
Description	`/sys/power/suspend_stats/failed_suspend`는 모든 non-sysdev devices의 `suspend` callbacks 실행이 실패한 횟수입니다.

System power sysfs ABI: failed suspend late

378-385

항목	한국어 전문 번역
What	/sys/power/suspend_stats/failed_suspend_late
Date	2019년 7월
KernelVersion
Contact	Kalesh Singh <[email protected]>
Description	`/sys/power/suspend_stats/failed_suspend_late`는 모든 devices의 `late suspend` callbacks 실행이 실패한 횟수입니다.

System power sysfs ABI: failed suspend noirq

386-393

항목	한국어 전문 번역
What	/sys/power/suspend_stats/failed_suspend_noirq
Date	2019년 7월
KernelVersion
Contact	Kalesh Singh <[email protected]>
Description	`/sys/power/suspend_stats/failed_suspend_noirq`는 모든 devices의 `noirq suspend` callbacks 실행이 실패한 횟수입니다.

System power sysfs ABI: last failed dev

394-400

항목	한국어 전문 번역
What	/sys/power/suspend_stats/last_failed_dev
Date	2019년 7월
KernelVersion
Contact	Kalesh Singh <[email protected]>
Description	`/sys/power/suspend_stats/last_failed_dev`는 suspend/resume callback이 마지막으로 실패한 device를 담습니다.

System power sysfs ABI: last failed errno

401-408

항목	한국어 전문 번역
What	/sys/power/suspend_stats/last_failed_errno
Date	2019년 7월
KernelVersion
Contact	Kalesh Singh <[email protected]>
Description	`/sys/power/suspend_stats/last_failed_errno`는 system sleep state 진입의 마지막 실패 attempt에서 나온 errno를 담습니다.

System power sysfs ABI: last failed step

409-415

항목	한국어 전문 번역
What	/sys/power/suspend_stats/last_failed_step
Date	2019년 7월
KernelVersion
Contact	Kalesh Singh <[email protected]>
Description	`/sys/power/suspend_stats/last_failed_step`은 suspend/resume path에서 마지막으로 실패한 step을 담습니다.

System power sysfs ABI: last hw sleep

416-424

항목	한국어 전문 번역
What	/sys/power/suspend_stats/last_hw_sleep
Date	2023년 6월
KernelVersion
Contact	Mario Limonciello <[email protected]>
Description	`/sys/power/suspend_stats/last_hw_sleep`은 가장 최근 system suspend-resume cycle에서 hardware sleep state에 머문 duration을 microseconds 단위로 담습니다.

Hardware sleep-time statistics

AttributeScope

last_hw_sleepMost recent suspend-resume cycle

total_hw_sleepAggregate since kernel boot

max_hw_sleepMaximum duration hardware can report

Accuracy limitCycles longer than max_hw_sleep may make last_hw_sleep and total_hw_sleep inaccurate.

모든 values는 microseconds 단위입니다.

System power sysfs ABI: total hw sleep

425-433

항목	한국어 전문 번역
What	/sys/power/suspend_stats/total_hw_sleep
Date	2023년 6월
KernelVersion
Contact	Mario Limonciello <[email protected]>
Description	`/sys/power/suspend_stats/total_hw_sleep`은 kernel boot 이후 hardware sleep state에 머문 aggregate time을 microseconds 단위로 담습니다.

System power sysfs ABI: max hw sleep

434-444

항목	한국어 전문 번역
What	/sys/power/suspend_stats/max_hw_sleep
Date	2023년 6월
KernelVersion
Contact	Mario Limonciello <[email protected]>
Description	`/sys/power/suspend_stats/max_hw_sleep`은 hardware가 sleep-state duration으로 보고할 수 있는 maximum time을 microseconds 단위로 담습니다. Sleep cycle이 이보다 길면 `total_hw_sleep`과 `last_hw_sleep` values가 정확하지 않을 수 있습니다.

System power sysfs ABI: sync on suspend

445-456

항목	한국어 전문 번역
What	/sys/power/sync_on_suspend
Date	2019년 10월
KernelVersion
Contact	Jonas Meurer <[email protected]>
Description	`/sys/power/sync_on_suspend`는 system suspend 중 userspace를 freeze한 뒤 devices를 suspend하기 전에 kernel이 filesystems에 `sync()`를 실행할지 제어합니다. `1`은 enable, `0`은 disable이며 read하면 current value를 반환합니다. Build-time `SUSPEND_SKIP_SYNC` config flag가 unset이면 default는 `1`, 그렇지 않으면 `0`입니다.