Article: Haswell TM Alternatives

Article: Haswell Transactional Memory Alternatives
By: David Kanter (, August 22, 2012 2:06 am
Room: Moderated Discussions
Håkan Winbom ( on August 22, 2012 12:52 am wrote:
> David Kanter ( on August 21, 2012 10:17 pm
> wrote:
> > We previously theorized that Intel’s TSX extensions in Haswell
> use the caches
> > to provide transactional memory semantics. This article
> describes an alternative
> > approach based on minimal changes to the CPU core
> (specifically in the ROB and
> > MOB), contrasts the advantages of the two
> techniques and discusses the expected
> > implementation in Haswell.
> >
> >
> >
> > I
> > also
> muse a bit about when these two techniques (cache-based and MOB-based TM)
> >
> will get implemented on the roadmap and how they can work together in a very
> > complimentary fashion.
> >
> > As always comments and discussion
> welcome.
> >
> > David
> I would really like a a high level use case
> description of transactional memory.
> Do you have any good reference? Or is that
> an entirely new article?
> /HW

There are a large number of use cases. To start with, Azul's JVM used a minimal form of TM to improve garbage collection.

Hardware Lock Elision is also quite useful for handling code with locks. For example, AMD did some excellent research showing considerable benefits for memcached:

< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
Article: Haswell TM AlternativesDavid Kanter08/21/12 10:17 PM
  Article: Haswell TM AlternativesHåkan Winbom08/22/12 12:52 AM
    Article: Haswell TM AlternativesDavid Kanter08/22/12 02:06 AM
  Article: Haswell TM Alternativesanon08/22/12 09:46 AM
    Article: Haswell TM AlternativesLinus Torvalds08/22/12 10:16 AM
      Article: Haswell TM AlternativesDoug S08/24/12 09:34 AM
    AMD's ASF even more limitedPaul A. Clayton08/22/12 10:20 AM
      AMD's ASF even more limitedLinus Torvalds08/22/12 10:41 AM
        Compiler use of ll/sc?Paul A. Clayton08/28/12 10:28 AM
          Compiler use of ll/sc?Linus Torvalds09/08/12 01:58 PM
            Lock recognition?Paul A. Clayton09/10/12 02:17 PM
              Sorry, I was confusedPaul A. Clayton09/13/12 11:56 AM
  Filter to detect store conflictsPaul A. Clayton08/22/12 10:19 AM
  Article: Haswell TM Alternativesbakaneko08/22/12 03:02 PM
    Article: Haswell TM AlternativesDavid Kanter08/22/12 03:45 PM
      Article: Haswell TM Alternativesbakaneko08/22/12 10:56 PM
  Cache line granularity?Paul A. Clayton08/28/12 10:28 AM
    Cache line granularity?David Kanter08/31/12 09:13 AM
      A looser definition might have advantagesPaul A. Clayton09/01/12 07:29 AM
    Cache line granularity?rwessel08/31/12 08:54 PM
      Alpha load locked granularityPaul A. Clayton09/01/12 07:29 AM
        Alpha load locked granularityanon09/02/12 06:23 PM
          Alpha pages groupsPaul A. Clayton09/03/12 05:16 AM
  An alternative implementationMaynard Handley11/20/12 10:52 PM
    An alternative implementationbakaneko11/21/12 06:52 AM
      Guarding unread values?Paul A. Clayton11/21/12 09:39 AM
        Guarding unread values?bakaneko11/21/12 12:25 PM
    TM granularity and versioningPaul A. Clayton11/21/12 09:27 AM
      TM granularity and versioningMaynard Handley11/21/12 11:52 AM
        Indeed, TM (and coherence) has devilish details (NT)Paul A. Clayton11/21/12 11:56 AM
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