Hi subhra, Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on tip/sched/core] [also build test WARNING on v4.17 next-20180612] [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/subhra-mazumdar/Improve-scheduler-scalability-for-fast-path/20180613-015158 config: i386-randconfig-x070-201823 (attached as .config) compiler: gcc-7 (Debian 7.3.0-16) 7.3.0 reproduce: # save the attached .config to linux build tree make ARCH=i386 All warnings (new ones prefixed by >>): kernel/sched/fair.c: In function 'select_idle_cpu': >> kernel/sched/fair.c:6396:3: warning: ISO C90 forbids mixed declarations and >> code [-Wdeclaration-after-statement] u64 span_avg = sd->span_weight * avg_idle; ^~~ vim +6396 kernel/sched/fair.c 10e2f1acd Peter Zijlstra 2016-05-09 6363 10e2f1acd Peter Zijlstra 2016-05-09 6364 /* 10e2f1acd Peter Zijlstra 2016-05-09 6365 * Scan the LLC domain for idle CPUs; this is dynamically regulated by 10e2f1acd Peter Zijlstra 2016-05-09 6366 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the 10e2f1acd Peter Zijlstra 2016-05-09 6367 * average idle time for this rq (as found in rq->avg_idle). 10e2f1acd Peter Zijlstra 2016-05-09 6368 */ 10e2f1acd Peter Zijlstra 2016-05-09 6369 static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target) 10e2f1acd Peter Zijlstra 2016-05-09 6370 { 9cfb38a7b Wanpeng Li 2016-10-09 6371 struct sched_domain *this_sd; 1ad3aaf3f Peter Zijlstra 2017-05-17 6372 u64 avg_cost, avg_idle; 10e2f1acd Peter Zijlstra 2016-05-09 6373 u64 time, cost; 10e2f1acd Peter Zijlstra 2016-05-09 6374 s64 delta; 8dd662615 subhra mazumdar 2018-06-12 6375 int cpu, limit, floor, nr = INT_MAX; 10e2f1acd Peter Zijlstra 2016-05-09 6376 9cfb38a7b Wanpeng Li 2016-10-09 6377 this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); 9cfb38a7b Wanpeng Li 2016-10-09 6378 if (!this_sd) 9cfb38a7b Wanpeng Li 2016-10-09 6379 return -1; 9cfb38a7b Wanpeng Li 2016-10-09 6380 10e2f1acd Peter Zijlstra 2016-05-09 6381 /* 10e2f1acd Peter Zijlstra 2016-05-09 6382 * Due to large variance we need a large fuzz factor; hackbench in 10e2f1acd Peter Zijlstra 2016-05-09 6383 * particularly is sensitive here. 10e2f1acd Peter Zijlstra 2016-05-09 6384 */ 1ad3aaf3f Peter Zijlstra 2017-05-17 6385 avg_idle = this_rq()->avg_idle / 512; 1ad3aaf3f Peter Zijlstra 2017-05-17 6386 avg_cost = this_sd->avg_scan_cost + 1; 1ad3aaf3f Peter Zijlstra 2017-05-17 6387 1ad3aaf3f Peter Zijlstra 2017-05-17 6388 if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost) 10e2f1acd Peter Zijlstra 2016-05-09 6389 return -1; 10e2f1acd Peter Zijlstra 2016-05-09 6390 1ad3aaf3f Peter Zijlstra 2017-05-17 6391 if (sched_feat(SIS_PROP)) { 8dd662615 subhra mazumdar 2018-06-12 6392 floor = cpumask_weight(topology_sibling_cpumask(target)); 8dd662615 subhra mazumdar 2018-06-12 6393 if (floor < 2) 8dd662615 subhra mazumdar 2018-06-12 6394 floor = 2; 8dd662615 subhra mazumdar 2018-06-12 6395 limit = 2*floor; 1ad3aaf3f Peter Zijlstra 2017-05-17 @6396 u64 span_avg = sd->span_weight * avg_idle; 8dd662615 subhra mazumdar 2018-06-12 6397 if (span_avg > floor*avg_cost) { 1ad3aaf3f Peter Zijlstra 2017-05-17 6398 nr = div_u64(span_avg, avg_cost); 8dd662615 subhra mazumdar 2018-06-12 6399 if (nr > limit) 8dd662615 subhra mazumdar 2018-06-12 6400 nr = limit; 8dd662615 subhra mazumdar 2018-06-12 6401 } else { 8dd662615 subhra mazumdar 2018-06-12 6402 nr = floor; 8dd662615 subhra mazumdar 2018-06-12 6403 } 1ad3aaf3f Peter Zijlstra 2017-05-17 6404 } 1ad3aaf3f Peter Zijlstra 2017-05-17 6405 10e2f1acd Peter Zijlstra 2016-05-09 6406 time = local_clock(); 10e2f1acd Peter Zijlstra 2016-05-09 6407 c743f0a5c Peter Zijlstra 2017-04-14 6408 for_each_cpu_wrap(cpu, sched_domain_span(sd), target) { 1ad3aaf3f Peter Zijlstra 2017-05-17 6409 if (!--nr) 1ad3aaf3f Peter Zijlstra 2017-05-17 6410 return -1; 0c98d344f Ingo Molnar 2017-02-05 6411 if (!cpumask_test_cpu(cpu, &p->cpus_allowed)) 10e2f1acd Peter Zijlstra 2016-05-09 6412 continue; 943d355d7 Rohit Jain 2018-05-09 6413 if (available_idle_cpu(cpu)) 10e2f1acd Peter Zijlstra 2016-05-09 6414 break; 10e2f1acd Peter Zijlstra 2016-05-09 6415 } 10e2f1acd Peter Zijlstra 2016-05-09 6416 10e2f1acd Peter Zijlstra 2016-05-09 6417 time = local_clock() - time; 10e2f1acd Peter Zijlstra 2016-05-09 6418 cost = this_sd->avg_scan_cost; 10e2f1acd Peter Zijlstra 2016-05-09 6419 delta = (s64)(time - cost) / 8; 10e2f1acd Peter Zijlstra 2016-05-09 6420 this_sd->avg_scan_cost += delta; 10e2f1acd Peter Zijlstra 2016-05-09 6421 10e2f1acd Peter Zijlstra 2016-05-09 6422 return cpu; 10e2f1acd Peter Zijlstra 2016-05-09 6423 } 10e2f1acd Peter Zijlstra 2016-05-09 6424 :::::: The code at line 6396 was first introduced by commit :::::: 1ad3aaf3fcd2444406628a19a9b9e0922b95e2d4 sched/core: Implement new approach to scale select_idle_cpu() :::::: TO: Peter Zijlstra <pet...@infradead.org> :::::: CC: Ingo Molnar <mi...@kernel.org> --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation
.config.gz
Description: application/gzip
