tests/wq_limits.c

   1 #include <sys/sysctl.h>
   2 #include <dispatch/dispatch.h>
   3 #include <dispatch/private.h>
   4 #include "darwintest_defaults.h"
   5
   6 T_DECL(wq_pool_limits, "test overcommit limit")
   7 {
   8         dispatch_semaphore_t sema = dispatch_semaphore_create(0);
   9         dispatch_group_t g = dispatch_group_create();
  10         dispatch_time_t t;
  11         uint32_t wq_max_threads, wq_max_constrained_threads;
  12
  13         dispatch_block_t b = ^{
  14                 dispatch_group_leave(g);
  15                 dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
  16         };
  17
  18         size_t s = sizeof(uint32_t);
  19         sysctlbyname("kern.wq_max_threads", &wq_max_threads, &s, NULL, 0);
  20         sysctlbyname("kern.wq_max_constrained_threads", &wq_max_constrained_threads,
  21                                  &s, NULL, 0);
  22
  23         for (uint32_t i = 0; i < wq_max_constrained_threads; i++) {
  24                 dispatch_group_enter(g);
  25                 dispatch_async(dispatch_get_global_queue(QOS_CLASS_DEFAULT, 0), b);
  26         }
  27
  28         t = dispatch_time(DISPATCH_TIME_NOW, 10 * NSEC_PER_SEC);
  29         T_ASSERT_EQ(dispatch_group_wait(g, t), 0L,
  30                         "%d constrained threads bringup", wq_max_constrained_threads);
  31
  32         dispatch_async(dispatch_get_global_queue(QOS_CLASS_DEFAULT, 0), ^{
  33                 T_ASSERT_FAIL("Should never run");
  34         });
  35
  36         sleep(5);
  37         T_PASS("constrained limit looks fine");
  38
  39         for (uint32_t i = wq_max_constrained_threads; i < wq_max_threads; i++) {
  40                 dispatch_group_enter(g);
  41                 dispatch_async(dispatch_get_global_queue(QOS_CLASS_DEFAULT,
  42                                                 DISPATCH_QUEUE_OVERCOMMIT), b);
  43         }
  44         t = dispatch_time(DISPATCH_TIME_NOW, 10 * NSEC_PER_SEC);
  45         T_ASSERT_EQ(dispatch_group_wait(g, t), 0L,
  46                         "%d threads bringup", wq_max_threads);
  47
  48
  49         dispatch_async(dispatch_get_global_queue(QOS_CLASS_DEFAULT,
  50                                         DISPATCH_QUEUE_OVERCOMMIT), ^{
  51                 T_ASSERT_FAIL("Should never run");
  52         });
  53
  54         sleep(5);
  55         T_PASS("thread limit looks fine");
  56         T_END;
  57 }