Fwd: [Haskell-cafe] Is there any experience using Software Transactional Memory in substantial applications?

[Alberto G. Corona]

---------- Forwarded message ----------
From: Alberto G. Corona <agocorona at gmail.com>
Date: 2010/8/8
Subject: Re: [Haskell-cafe] Is there any experience using Software
Transactional Memory in substantial applications?
To: Serguey Zefirov <sergueyz at gmail.com>


This first papers is the first that describes the preliminary haskell
implementation and the performance data says that STM scales well with the
number of CPU cores  Blocking does not scale, as expected.

http://research.microsoft.com/en-us/um/people/simonpj/papers/stm/lock-free-flops06.pdf

In this other study, also for microsoft:

<http://research.microsoft.com/en-us/um/people/simonpj/papers/stm/lock-free-flops06.pdf>
 Dissecting Transactional Executions in
Haskell<http://www.cs.rochester.edu/meetings/TRANSACT07/papers/perfumo.pdf>
.

The worst performance  in the study is from an extreme case example form my
package TCache described
here<http://haskell-web.blogspot.com/2006/11/transactional-cache-for-haskell.html>.
In that example,  a set of treads update the same two objects all the time.
Since STM is non  blocking, all threads tries to perform the task and
rollback at the very end if things have been changed by other thread in the
meantime. Just like databases. The bad thing is that the more CPU cores are
executing the example, the more work being rolled back is done. That is more
or less the history.

 I heard (The Monad Reader -mplementing STM in pure
Haskell<http://themonadreader.files.wordpress.com/2010/01/issue15.pdf>)
  about other tentative implementation that do not wait for the end of the
atomic task to test the atomicity of the transaction, but instead, any
update of a TVar inmediately invalidates (and kill) all  atomic transactions
that uses that TVar. This could potentially improve the performance a lot.

However I don´t know the strategy of the current haskell implementation nor
the strasategy of the Microsoft runtime(s) either.

Anyway, it is waranteed 100% that 1) the slowest in memory transaction is
way faster than the transaction delegated to the fastest external database.
 2) in memory transactions with blocking is a nightmare. For me  these are
enough arguments for  STM usage in many ordinary (I mean Web) applications.


2010/8/8 Serguey Zefirov <sergueyz at gmail.com>

Recently we discussed Haskell and especially types in Russian part of
> LiveJournal and of course we talk about STM.
>
> My opponent gave me that link:
>
> http://logicaloptimizer.blogspot.com/2010/06/so-microsofts-experiments-with-software.html
>
> It says that performance with STM in Microsoft Research was more than
> horrible.
>
> I failed to find convincing counter-evidence on the web. Not for
> Haskell, even for Java/C#/C++.
>
> So I asking Haskell-cafe for clarification. Do anyone here have an
> experience with STM in computing-intensive tasks? Did it help there?
> What are the possible reasons for STM failure in MR?
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