A minimal, bounded hardware transactional memory implementation

significantly improves synchronization performance

when used in an operating system kernel. We add

HTM to Linux 2.4, a kernel with a simple, coarse-grained

synchronization structure. The transactional Linux 2.4 kernel

can improve performance of user programs by as much

as 40% over the non-transactional 2.4 kernel. It closes 68%

of the performance gap with the Linux 2.6 kernel, which has

had significant engineering effort applied to improve scalability.

We then extend our minimal HTM to a fast, unbounded

transactional memory with a novel technique for coordinating

hardware transactions and software synchronization.

Overflowed transactions run in software, with only a minimal

coupling between hardware and software systems. There

is no performance penalty for overflow rates of less than 1%.

In one instance, at 16 processors and an overflow rate of 4%,

performance degrades from an ideal 4.3× to 3.6×.

In  ASPLOS

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