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

kernel test robot lkp at intel.com
Thu Jun 9 03:14:59 PDT 2022


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 at 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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