Re: [PATCH v3 2/2] sched/fair: Scan cluster before scanning LLC in wake-up path

kernel test robot
2022-06-09T10:15:56Z

Hi Yicong,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on tip/sched/core]
[also build test WARNING on linus/master v5.19-rc1 next-20220609]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url: https://github.com/intel-lab-lkp/linux/commits/Yicong-Yang/sched-fair-Wake-task-within-the-cluster-when-possible/20220608-181847
base: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git 991d8d8142cad94f9c5c05db25e67fa83d6f772a
config: x86_64-randconfig-a006 (https://download.01.org/0day-ci/archive/20220609/202206091846.fm1bYjWk-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
reproduce (this is a W=1 build):
# https://github.com/intel-lab-lkp/linux/commit/f2b15e8641f351783c1d47bc654ace164300b7f1
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Yicong-Yang/sched-fair-Wake-task-within-the-cluster-when-possible/20220608-181847
git checkout f2b15e8641f351783c1d47bc654ace164300b7f1
# save the config file
mkdir build_dir && cp config build_dir/.config
make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash kernel/sched/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

kernel/sched/fair.c: In function 'select_idle_cpu':
>> kernel/sched/fair.c:6381:36: warning: passing argument 2 of 'scan_cluster' makes integer from pointer without a cast [-Wint-conversion]
6381 | idle_cpu = scan_cluster(p, cpus, target, &nr);
| ^~~~
| |
| struct cpumask *
kernel/sched/fair.c:6327:59: note: expected 'int' but argument is of type 'struct cpumask *'
6327 | static inline int scan_cluster(struct task_struct *p, int prev_cpu, int target, int *nr)
| ~~~~^~~~~~~~
kernel/sched/fair.c: At top level:
kernel/sched/fair.c:11114:6: warning: no previous prototype for 'task_vruntime_update' [-Wmissing-prototypes]
11114 | void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi)
| ^~~~~~~~~~~~~~~~~~~~

vim +/scan_cluster +6381 kernel/sched/fair.c

6332
6333 /*
6334 * Scan the LLC domain for idle CPUs; this is dynamically regulated by
6335 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
6336 * average idle time for this rq (as found in rq->avg_idle).
6337 */
6338 static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool has_idle_core, int target)
6339 {
6340 struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
6341 int i, cpu, idle_cpu = -1, nr = INT_MAX;
6342 struct rq *this_rq = this_rq();
6343 int this = smp_processor_id();
6344 struct sched_domain *this_sd;
6345 u64 time = 0;
6346
6347 this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
6348 if (!this_sd)
6349 return -1;
6350
6351 cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
6352
6353 if (sched_feat(SIS_PROP) && !has_idle_core) {
6354 u64 avg_cost, avg_idle, span_avg;
6355 unsigned long now = jiffies;
6356
6357 /*
6358 * If we're busy, the assumption that the last idle period
6359 * predicts the future is flawed; age away the remaining
6360 * predicted idle time.
6361 */
6362 if (unlikely(this_rq->wake_stamp < now)) {
6363 while (this_rq->wake_stamp < now && this_rq->wake_avg_idle) {
6364 this_rq->wake_stamp++;
6365 this_rq->wake_avg_idle >>= 1;
6366 }
6367 }
6368
6369 avg_idle = this_rq->wake_avg_idle;
6370 avg_cost = this_sd->avg_scan_cost + 1;
6371
6372 span_avg = sd->span_weight * avg_idle;
6373 if (span_avg > 4*avg_cost)
6374 nr = div_u64(span_avg, avg_cost);
6375 else
6376 nr = 4;
6377
6378 time = cpu_clock(this);
6379 }
6380
> 6381 idle_cpu = scan_cluster(p, cpus, target, &nr);
6382 if ((unsigned int)idle_cpu < nr_cpumask_bits)
6383 return idle_cpu;
6384
6385 for_each_cpu_wrap(cpu, cpus, target + 1) {
6386 if (has_idle_core) {
6387 i = select_idle_core(p, cpu, cpus, &idle_cpu);
6388 if ((unsigned int)i < nr_cpumask_bits)
6389 return i;
6390
6391 } else {
6392 if (--nr <= 0)
6393 return -1;
6394 idle_cpu = __select_idle_cpu(cpu, p);
6395 if ((unsigned int)idle_cpu < nr_cpumask_bits)
6396 break;
6397 }
6398 }
6399
6400 if (has_idle_core)
6401 set_idle_cores(target, false);
6402
6403 if (sched_feat(SIS_PROP) && !has_idle_core) {
6404 time = cpu_clock(this) - time;
6405
6406 /*
6407 * Account for the scan cost of wakeups against the average
6408 * idle time.
6409 */
6410 this_rq->wake_avg_idle -= min(this_rq->wake_avg_idle, time);
6411
6412 update_avg(&this_sd->avg_scan_cost, time);
6413 }
6414
6415 return idle_cpu;
6416 }
6417

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