xv6 is a modern reimplementation of Sixth Edition Unix in ANSI C for multiprocessor x86 and RISC-V systems. It was created for pedagogical purposes in MIT's Operating System Engineering course. Wikipedia
For the final project of the Operating Systems course (Fall 2020, instructed by Dr. Seyed Ahmad Javadi), We (danialzz and i) added some additional features to xv6. Our work mainly includes adding process scheduling algorithms (such as Priority, Reverse priority, Round Robin, and MultiLayered Queue scheduling), and also some useful system calls (i.e. getParentID, getChildren, getSyscallCounter, ...). The full documentation of the project can be found here and here.