I try to count IOPS and I/O size with SystemTap script and use MySQL to be workload.I found mysqld doesn't call systemcall but mysqld has read/write on VFS.So, do MySQL processes run in user or kernel modes?
Does MySQL processes run in user or kernel modes?
kernel;mysql;system calls
Mysql doesn't have a kernel module, therefore it runs in user mode.Perhaps what you are seeing is that mysql is using memory-mapped files instead of calling read/write.  So, accessing a page of memory causes a read/write without using a syscall.Or, perhaps you called strace without -f to follow the child processes?