streamich (@streamich) started discussion #94
We already know what is a system call. This is special routine in the Linux kernel which userspace application asks to do privileged tasks, like to read or to write to a file, to open a socket and etc. As you may know, invoking a system call is an expensive operation in the Linux kernel, because the processor must interrupt the currently executing task and switch context to kernel mode, subsequently jumping again into userspace after the system call handler finishes its work. These two mechanisms - vsyscall and vdso are designed to speed up this process for certain system calls and in this part we will try to understand how these mechanisms work.