Hi kselftests is integrated Intel 0Day project. Sometimes we found compaction_test is blocked for more than 1 hours until i kill it. Try to figure out where it is running, i added some log to this case. the test log is like: ------------------- [ 111.750543] main: 248 [ 111.750544]- [ 111.750821] check_compaction: 98 [ 111.750822]- [ 111.751102] check_compaction: 105 [ 111.751103]- [ 111.751362] check_compaction: 111 [ 111.751363]- [ 111.751621] check_compaction: 118 [ 111.751622]- [ 111.751879] check_compaction: 123 [ 111.751880]- ------------------- 118 fprintf(stderr, "%s: %d\n", __func__, __LINE__); 119 lseek(fd, 0, SEEK_SET); 120 121 /* Request a large number of huge pages. The Kernel will allocate 122 as much as it can */ 123 fprintf(stderr, "%s: %d\n", __func__, __LINE__); <<<======== the last line we can catch. 124 if (write(fd, "100000", (6*sizeof(char))) != (6*sizeof(char))) { <<<<============ blocking position 125 perror("Failed to write 100000 to /proc/sys/vm/nr_hugepages\n"); 126 goto close_fd; 127 } 128 129 lseek(fd, 0, SEEK_SET); 130 131 fprintf(stderr, "%s: %d\n", __func__, __LINE__); 132 if (read(fd, nr_hugepages, sizeof(nr_hugepages)) <= 0) { 133 perror("Failed to re-read from /proc/sys/vm/nr_hugepages\n"); 134 goto close_fd; 135 } ------------------- According to above log and code, it most likely it is blocking at the writing operation. my environment is like: OS: debian kernel: v4.15 model: Ivytown Ivy Bridge-EP nr_cpu: 48 memory: 64G NOTE: 0Day can reproduce this issue in 20% on 0Day. Anybody can help have a look? Thanks Zhjian -- To unsubscribe from this list: send the line "unsubscribe linux-kselftest" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html