STM - Next level #863
STM - Next level #863
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| for { | ||
| surplus <- IO.effectTotal { | ||
| val as = unsafeOfferAll(queue, remaining.toList) | ||
| unsafeCompleteTakers |
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You need to add () otherwise dotty complains.
Nice simplification!
| def suspend(journal: Journal): Unit = { | ||
| addTodo(txnId, journal, () => tryCommitAsync(null, platform, stm, txnId, done)(k)) | ||
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| if (isInvalid(journal)) tryCommit(platform, stm) match { |
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Everything is super clean, but I don't understand this line. Isn't it redundant with the line above?
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In between the time when the STM was executed and the "todo" was added, it may happen that the variables underlying the transaction have changed (by some other transaction), and the "todo" lists cleared by that transaction. In this case, the suspended transaction would never be retried. This line detects this case, and re-runs the transaction again if necessary.
This way of structuring the code allows dramatic minimization of the commit lock, albeit at the cost of trickier reasoning about correctness.
A little light airplane coding to improve performance of STM, as well as Promise and Queue. A quick look at Queue reveals lots of low hanging fruit. STM is getting in good shape (performance competitive with and in some cases better than
Ref+Promise) but still needs some intelligence around overlapping retries.