Advanced Search

Hardware Transactional Memory

Research and Teaching Output of the MIT Community

Show simple item record Lie, Sean Asanovic, Krste Kuszmaul, Bradley C. Leiserson, Charles E. 2003-12-13T19:21:30Z 2003-12-13T19:21:30Z 2004-01
dc.description.abstract This work shows how hardware transactional memory (HTM) can be implemented to support transactions of arbitrarily large size, while ensuring that small transactions run efficiently. Our implementation handles small transactions similar to Herlihy and Moss's scheme in that it holds tentative updates in a cache. Unlike their scheme, which uses a special fully associative cache, ours augments the ordinary processor cache and provides a mechanism to handle cache spills of uncommitted transactional data. Consequently, our scheme runs faster for small transactions while correctly handling transactions of arbitrarily large size. <br/>Although transactions are small in the common case, we argue that HTM should not restrict the size of transactions, because it complicates the programmer/compiler model and precludes some important programs from exploiting transactional memory. We show that the Linux 2.4.19 kernel can be automatically and efficiently “transactified” if boundless transactions can be supported. Our experimental results show that the largest transaction touches over 7000 64-byte cache lines, whereas 99.94\% of the transactions touch fewer than 64 cache lines. We further show that synchronized methods in Java can be easily compiled to our HTM scheme, thereby providing the advantages of nonblocking atomicity (including absence of deadlock) in a straightforward fashion. Our HTM scheme for boundless transactions uses an efficiently implementable hardware snapshot and the ordinary set-associative L2 cache extended with less than two bits per cache line. One of the bits tells whether the cached item is part of a transaction (as in the Herlihy-Moss scheme), and all the lines in an associative set share another bit telling whether a line has overflowed from the cache and is now stored in a special overflow area of main memory. We provide empirical results to show that our scheme does not adversely affect the processor pipeline or hinder speculative execution. en
dc.description.sponsorship Singapore-MIT Alliance (SMA) en
dc.format.extent 12684 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.relation.ispartofseries Computer Science (CS);
dc.subject hardware transactional memory en
dc.subject boundless transactions en
dc.subject nonblocking atomicity en
dc.title Hardware Transactional Memory en
dc.type Article en

Files in this item

Name Size Format Description
CS027.pdf 12.38Kb PDF

This item appears in the following Collection(s)

Show simple item record