Hi Rafael, I love your patch! Perhaps something to improve:
[auto build test WARNING on pm/linux-next] [also build test WARNING on v4.18-rc8 next-20180810] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system] url: https://github.com/0day-ci/linux/commits/Rafael-J-Wysocki/cpuidle-menu-Handle-stopped-tick-more-aggressively/20180811-191914 base: https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git linux-next config: mips-allyesconfig (attached as .config) compiler: mips-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0 reproduce: wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # save the attached .config to linux build tree GCC_VERSION=7.2.0 make.cross ARCH=mips Note: it may well be a FALSE warning. FWIW you are at least aware of it now. http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings All warnings (new ones prefixed by >>): drivers/cpuidle/governors/menu.c: In function 'menu_select': >> drivers/cpuidle/governors/menu.c:289:6: warning: 'first_idx' may be used >> uninitialized in this function [-Wmaybe-uninitialized] int first_idx; ^~~~~~~~~ vim +/first_idx +289 drivers/cpuidle/governors/menu.c 1f85f87d4 Arjan van de Ven 2010-05-24 276 4f86d3a8e Len Brown 2007-10-03 277 /** 4f86d3a8e Len Brown 2007-10-03 278 * menu_select - selects the next idle state to enter 46bcfad7a Deepthi Dharwar 2011-10-28 279 * @drv: cpuidle driver containing state data 4f86d3a8e Len Brown 2007-10-03 280 * @dev: the CPU 45f1ff59e Rafael J. Wysocki 2018-03-22 281 * @stop_tick: indication on whether or not to stop the tick 4f86d3a8e Len Brown 2007-10-03 282 */ 45f1ff59e Rafael J. Wysocki 2018-03-22 283 static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, 45f1ff59e Rafael J. Wysocki 2018-03-22 284 bool *stop_tick) 4f86d3a8e Len Brown 2007-10-03 285 { 229b6863b Christoph Lameter 2014-08-17 286 struct menu_device *data = this_cpu_ptr(&menu_devices); 0fc784fb0 Rafael J. Wysocki 2018-05-30 287 int latency_req = cpuidle_governor_latency_req(dev->cpu); 4f86d3a8e Len Brown 2007-10-03 288 int i; 3ed09c945 Nicholas Piggin 2017-06-26 @289 int first_idx; 3ed09c945 Nicholas Piggin 2017-06-26 290 int idx; 96e95182e tuukka.tikka...@linaro.org 2014-02-24 291 unsigned int interactivity_req; e132b9b3b Rik van Riel 2016-03-16 292 unsigned int expected_interval; 372ba8cb4 Mel Gorman 2014-08-06 293 unsigned long nr_iowaiters, cpu_load; 296bb1e51 Rafael J. Wysocki 2018-04-05 294 ktime_t delta_next; 4f86d3a8e Len Brown 2007-10-03 295 672917dcc Corrado Zoccolo 2009-09-21 296 if (data->needs_update) { 46bcfad7a Deepthi Dharwar 2011-10-28 297 menu_update(drv, dev); 672917dcc Corrado Zoccolo 2009-09-21 298 data->needs_update = 0; 672917dcc Corrado Zoccolo 2009-09-21 299 } 672917dcc Corrado Zoccolo 2009-09-21 300 69d25870f Arjan van de Ven 2009-09-21 301 /* Special case when user has set very strict latency requirement */ 45f1ff59e Rafael J. Wysocki 2018-03-22 302 if (unlikely(latency_req == 0)) { 45f1ff59e Rafael J. Wysocki 2018-03-22 303 *stop_tick = false; a2bd92023 venkatesh.pallip...@intel.com 2008-07-30 304 return 0; 45f1ff59e Rafael J. Wysocki 2018-03-22 305 } a2bd92023 venkatesh.pallip...@intel.com 2008-07-30 306 69d25870f Arjan van de Ven 2009-09-21 307 /* determine the expected residency time, round up */ 296bb1e51 Rafael J. Wysocki 2018-04-05 308 data->next_timer_us = ktime_to_us(tick_nohz_get_sleep_length(&delta_next)); 69d25870f Arjan van de Ven 2009-09-21 309 5f9f09809 Rafael J. Wysocki 2018-08-10 310 /* 5f9f09809 Rafael J. Wysocki 2018-08-10 311 * If the tick is already stopped, the cost of possible short idle 5f9f09809 Rafael J. Wysocki 2018-08-10 312 * duration misprediction is much higher, because the CPU may be stuck 5f9f09809 Rafael J. Wysocki 2018-08-10 313 * in a shallow idle state for a long time as a result of it. In that 5f9f09809 Rafael J. Wysocki 2018-08-10 314 * case say we might mispredict and use the known time till the closest 5f9f09809 Rafael J. Wysocki 2018-08-10 315 * timer event for the idle state selection. 5f9f09809 Rafael J. Wysocki 2018-08-10 316 */ 5f9f09809 Rafael J. Wysocki 2018-08-10 317 if (tick_nohz_tick_stopped()) { 5f9f09809 Rafael J. Wysocki 2018-08-10 318 data->predicted_us = ktime_to_us(delta_next); 5f9f09809 Rafael J. Wysocki 2018-08-10 319 goto select; 5f9f09809 Rafael J. Wysocki 2018-08-10 320 } 5f9f09809 Rafael J. Wysocki 2018-08-10 321 372ba8cb4 Mel Gorman 2014-08-06 322 get_iowait_load(&nr_iowaiters, &cpu_load); 64b4ca5cb Mel Gorman 2014-08-06 323 data->bucket = which_bucket(data->next_timer_us, nr_iowaiters); 69d25870f Arjan van de Ven 2009-09-21 324 69d25870f Arjan van de Ven 2009-09-21 325 /* 51f245b89 Tuukka Tikkanen 2013-08-14 326 * Force the result of multiplication to be 64 bits even if both 51f245b89 Tuukka Tikkanen 2013-08-14 327 * operands are 32 bits. 51f245b89 Tuukka Tikkanen 2013-08-14 328 * Make sure to round up for half microseconds. 51f245b89 Tuukka Tikkanen 2013-08-14 329 */ ee3c86f35 Javi Merino 2015-04-16 330 data->predicted_us = DIV_ROUND_CLOSEST_ULL((uint64_t)data->next_timer_us * 51f245b89 Tuukka Tikkanen 2013-08-14 331 data->correction_factor[data->bucket], 69d25870f Arjan van de Ven 2009-09-21 332 RESOLUTION * DECAY); 69d25870f Arjan van de Ven 2009-09-21 333 e132b9b3b Rik van Riel 2016-03-16 334 expected_interval = get_typical_interval(data); e132b9b3b Rik van Riel 2016-03-16 335 expected_interval = min(expected_interval, data->next_timer_us); 96e95182e tuukka.tikka...@linaro.org 2014-02-24 336 dc2251bf9 Rafael J. Wysocki 2017-08-23 337 first_idx = 0; dc2251bf9 Rafael J. Wysocki 2017-08-23 338 if (drv->states[0].flags & CPUIDLE_FLAG_POLLING) { dc2251bf9 Rafael J. Wysocki 2017-08-23 339 struct cpuidle_state *s = &drv->states[1]; 0c313cb20 Rafael J. Wysocki 2016-03-20 340 unsigned int polling_threshold; 0c313cb20 Rafael J. Wysocki 2016-03-20 341 96e95182e tuukka.tikka...@linaro.org 2014-02-24 342 /* 69d25870f Arjan van de Ven 2009-09-21 343 * We want to default to C1 (hlt), not to busy polling e132b9b3b Rik van Riel 2016-03-16 344 * unless the timer is happening really really soon, or e132b9b3b Rik van Riel 2016-03-16 345 * C1's exit latency exceeds the user configured limit. 69d25870f Arjan van de Ven 2009-09-21 346 */ 0c313cb20 Rafael J. Wysocki 2016-03-20 347 polling_threshold = max_t(unsigned int, 20, s->target_residency); 0c313cb20 Rafael J. Wysocki 2016-03-20 348 if (data->next_timer_us > polling_threshold && 0c313cb20 Rafael J. Wysocki 2016-03-20 349 latency_req > s->exit_latency && !s->disabled && dc2251bf9 Rafael J. Wysocki 2017-08-23 350 !dev->states_usage[1].disable) dc2251bf9 Rafael J. Wysocki 2017-08-23 351 first_idx = 1; 9c4b2867e Rafael J. Wysocki 2016-01-14 352 } 4f86d3a8e Len Brown 2007-10-03 353 71abbbf85 Ai Li 2010-08-09 354 /* e132b9b3b Rik van Riel 2016-03-16 355 * Use the lowest expected idle interval to pick the idle state. e132b9b3b Rik van Riel 2016-03-16 356 */ e132b9b3b Rik van Riel 2016-03-16 357 data->predicted_us = min(data->predicted_us, expected_interval); e132b9b3b Rik van Riel 2016-03-16 358 e132b9b3b Rik van Riel 2016-03-16 359 /* 5f9f09809 Rafael J. Wysocki 2018-08-10 360 * Use the performance multiplier and the user-configurable latency_req 5f9f09809 Rafael J. Wysocki 2018-08-10 361 * to determine the maximum exit latency. e132b9b3b Rik van Riel 2016-03-16 362 */ e132b9b3b Rik van Riel 2016-03-16 363 interactivity_req = data->predicted_us / performance_multiplier(nr_iowaiters, cpu_load); e132b9b3b Rik van Riel 2016-03-16 364 if (latency_req > interactivity_req) e132b9b3b Rik van Riel 2016-03-16 365 latency_req = interactivity_req; e132b9b3b Rik van Riel 2016-03-16 366 5f9f09809 Rafael J. Wysocki 2018-08-10 367 select: 45f1ff59e Rafael J. Wysocki 2018-03-22 368 expected_interval = data->predicted_us; e132b9b3b Rik van Riel 2016-03-16 369 /* 71abbbf85 Ai Li 2010-08-09 370 * Find the idle state with the lowest power while satisfying 71abbbf85 Ai Li 2010-08-09 371 * our constraints. 71abbbf85 Ai Li 2010-08-09 372 */ 3ed09c945 Nicholas Piggin 2017-06-26 373 idx = -1; 3ed09c945 Nicholas Piggin 2017-06-26 374 for (i = first_idx; i < drv->state_count; i++) { 46bcfad7a Deepthi Dharwar 2011-10-28 375 struct cpuidle_state *s = &drv->states[i]; dc7fd275a ShuoX Liu 2012-07-03 376 struct cpuidle_state_usage *su = &dev->states_usage[i]; 4f86d3a8e Len Brown 2007-10-03 377 cbc9ef028 Rafael J. Wysocki 2012-07-03 378 if (s->disabled || su->disable) 3a53396b0 ShuoX Liu 2012-03-28 379 continue; 3ed09c945 Nicholas Piggin 2017-06-26 380 if (idx == -1) 3ed09c945 Nicholas Piggin 2017-06-26 381 idx = i; /* first enabled state */ 148519120 Rafael J. Wysocki 2013-07-27 382 if (s->target_residency > data->predicted_us) 8e37e1a2a Alex Shi 2017-01-12 383 break; 45f1ff59e Rafael J. Wysocki 2018-03-22 384 if (s->exit_latency > latency_req) { 45f1ff59e Rafael J. Wysocki 2018-03-22 385 /* 45f1ff59e Rafael J. Wysocki 2018-03-22 386 * If we break out of the loop for latency reasons, use 45f1ff59e Rafael J. Wysocki 2018-03-22 387 * the target residency of the selected state as the 45f1ff59e Rafael J. Wysocki 2018-03-22 388 * expected idle duration so that the tick is retained 45f1ff59e Rafael J. Wysocki 2018-03-22 389 * as long as that target residency is low enough. 45f1ff59e Rafael J. Wysocki 2018-03-22 390 */ 45f1ff59e Rafael J. Wysocki 2018-03-22 391 expected_interval = drv->states[idx].target_residency; 8e37e1a2a Alex Shi 2017-01-12 392 break; 45f1ff59e Rafael J. Wysocki 2018-03-22 393 } 3ed09c945 Nicholas Piggin 2017-06-26 394 idx = i; 71abbbf85 Ai Li 2010-08-09 395 } 4f86d3a8e Len Brown 2007-10-03 396 3ed09c945 Nicholas Piggin 2017-06-26 397 if (idx == -1) 3ed09c945 Nicholas Piggin 2017-06-26 398 idx = 0; /* No states enabled. Must use 0. */ 3ed09c945 Nicholas Piggin 2017-06-26 399 45f1ff59e Rafael J. Wysocki 2018-03-22 400 /* 45f1ff59e Rafael J. Wysocki 2018-03-22 401 * Don't stop the tick if the selected state is a polling one or if the 45f1ff59e Rafael J. Wysocki 2018-03-22 402 * expected idle duration is shorter than the tick period length. 45f1ff59e Rafael J. Wysocki 2018-03-22 403 */ 5f9f09809 Rafael J. Wysocki 2018-08-10 404 if (((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) || 5f9f09809 Rafael J. Wysocki 2018-08-10 405 expected_interval < TICK_USEC) && !tick_nohz_tick_stopped()) { 296bb1e51 Rafael J. Wysocki 2018-04-05 406 unsigned int delta_next_us = ktime_to_us(delta_next); 296bb1e51 Rafael J. Wysocki 2018-04-05 407 45f1ff59e Rafael J. Wysocki 2018-03-22 408 *stop_tick = false; 45f1ff59e Rafael J. Wysocki 2018-03-22 409 5f9f09809 Rafael J. Wysocki 2018-08-10 410 if (idx > 0 && drv->states[idx].target_residency > delta_next_us) { 296bb1e51 Rafael J. Wysocki 2018-04-05 411 /* 296bb1e51 Rafael J. Wysocki 2018-04-05 412 * The tick is not going to be stopped and the target 296bb1e51 Rafael J. Wysocki 2018-04-05 413 * residency of the state to be returned is not within 296bb1e51 Rafael J. Wysocki 2018-04-05 414 * the time until the next timer event including the 296bb1e51 Rafael J. Wysocki 2018-04-05 415 * tick, so try to correct that. 296bb1e51 Rafael J. Wysocki 2018-04-05 416 */ 296bb1e51 Rafael J. Wysocki 2018-04-05 417 for (i = idx - 1; i >= 0; i--) { 296bb1e51 Rafael J. Wysocki 2018-04-05 418 if (drv->states[i].disabled || 296bb1e51 Rafael J. Wysocki 2018-04-05 419 dev->states_usage[i].disable) 296bb1e51 Rafael J. Wysocki 2018-04-05 420 continue; 296bb1e51 Rafael J. Wysocki 2018-04-05 421 296bb1e51 Rafael J. Wysocki 2018-04-05 422 idx = i; 296bb1e51 Rafael J. Wysocki 2018-04-05 423 if (drv->states[i].target_residency <= delta_next_us) 296bb1e51 Rafael J. Wysocki 2018-04-05 424 break; 296bb1e51 Rafael J. Wysocki 2018-04-05 425 } 296bb1e51 Rafael J. Wysocki 2018-04-05 426 } 296bb1e51 Rafael J. Wysocki 2018-04-05 427 } 296bb1e51 Rafael J. Wysocki 2018-04-05 428 3ed09c945 Nicholas Piggin 2017-06-26 429 data->last_state_idx = idx; 3ed09c945 Nicholas Piggin 2017-06-26 430 69d25870f Arjan van de Ven 2009-09-21 431 return data->last_state_idx; 4f86d3a8e Len Brown 2007-10-03 432 } 4f86d3a8e Len Brown 2007-10-03 433 :::::: The code at line 289 was first introduced by commit :::::: 3ed09c94580de9d5b18cc35d1f97e9f24cd9233b cpuidle: menu: allow state 0 to be disabled :::::: TO: Nicholas Piggin <npig...@gmail.com> :::::: CC: Rafael J. Wysocki <rafael.j.wyso...@intel.com> --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation
.config.gz
Description: application/gzip
