Hi all, I'm working on debuging a problem. The testcase does follew operations: 1) create a test task cgroup, set cpu.cfs_quota_us=2000,cpu.cfs_period_us=100000. 2) run 20 test_fork[1] test process in the test task cgroup. 3) create 100 new containers: for i in {1..100}; do docker run -itd --health-cmd="ls" --health-interval=1s ubuntu:latest bash; done These operations are expected to succeed and 100 containers create success. however, when creating containers, the system will get stuck and create container failed. After debug this, I found the test_fork process frequently sleep in freezer_fork()->mutex_lock()->might_sleep() with taking the cgroup_threadgroup_rw_sem lock, as follow: copy_process(): cgroup_can_fork() ---> lock cgroup_threadgroup_rw_sem sched_cgroup_fork(); ->task_fork_fair(){ ->update_curr(){ ->__account_cfs_rq_runtime() { resched_curr(); ---> the quota is used up, and set flag TIF_NEED_RESCHED to current } cgroup_post_fork(); ->feezer_fork() ->mutex_lock() { ->might_sleep() ---> schedule() and the current task will be throttled long time. ->cgroup_css_set_put_fork() ---> unlock cgroup_threadgroup_rw_sem Becuase the task cgroup's cpu.cfs_quota_us is very small and test_fork's load is very heavy, the test_fork may be throttled long time, therefore, the cgroup_threadgroup_rw_sem read lock is held for a long time, other processes will get stuck waiting for the lock: 1) a task fork child, will wait at copy_process()->cgroup_can_fork(); 2) a task exiting will wait at exit_signals(); 3) a task write cgroup.procs file will wait at cgroup_file_write()->__cgroup1_procs_write(); ... even the whole system will get stuck. Anyone know how to slove this? Except for changing the cpu.cfs_quota_us. [1] test_fork.c #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <sys/wait.h> int main(int argc, char **argv) { pid_t pid; int count = 20; while(1) { for (int i = 0; i < count; i++) { if ((pid = fork()) <0) { printf("fork error"); return 1; } else if (pid ==0) { exit(0); } } for (int i = 0; i < count; i++) { wait(NULL); } sleep(1); } return 0; } Thanks a lot. -Qiao -