---------- Forwarded message ----------
From:
Alberto G. Corona <agocorona@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@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:
The worst performance in the study is from an extreme case example form my package TCache described here. 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) 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.