Txlinux: using and managing hardware transactional memory in an operating system

TxLinux is a variant of Linux that is the first operating system to use hardware transactional memory (HTM) as a synchronization primitive, and the first to manage HTM in the scheduler. This paper describes and measures TxLinux and discusses two innovations in detail: cooperation between locks and transactions, and the integra-tion of transactions with the OS scheduler. Mixing locks and trans-actions requires a new primitive, cooperative transactional spin-locks (cxspinlocks) that allow locks and transactions to protect the same data while maintaining the advantages of both synchroniza-tion primitives. Cxspinlocks allow the system to attempt execution of critical regions with transactions and automatically roll back to use locking if the region performs I/O. Integrating the scheduler with HTM eliminates priority inversion. On a series of real-world benchmarks TxLinux has similar performance to Linux, exposing concurrency with as many as 32 concurrent threads on 32 CPUs in the same critical region