RE: [Haskell-cafe] Killer pickler combinators (was Time leak)

From: Joel Reymont To: Haskell-Cafe Cafe Subject: [Haskell-cafe] Killer pickler combinators (was Time leak) Date: Wed, 21 Dec 2005 02:39:43 +0000

The original paper is at http://research.microsoft.com/ ~akenn/fun/ picklercombinators.pdf

My adaptation is at http://wagerlabs.com/timeleak.tgz. This is a full repro case, data included.

The issue is that with 1000 threads my serialization is taking a few seconds.

Inserting a delay or passing in trace (see README and code) gets serialization time down to 0-1s, the way it should be.

What gives? Try it for yourself and please let me know!

This has easy explanation. I am learning haskell and your programs are great of that. In this code: do TOD time1 _ <- getClockTime (kind, ix1) <- unpickle puCmdType ptr ix TOD time2 _ <- getClockTime (cmd', _) <- unpickle (puCommand kind) ptr ix1 TOD time3 _ <- getClockTime you get time multiple times. So if you lock whole operation nothing else will be executed while in this code and therefore you don;t have timeouts. But, without lock more threads you have, more time have to wait for operation to finish and therefore timeouts. Since I see that Haskell executes all this in single thread, lock just ensures that your operasion will not be interrupted, thereferore not time outs. But if you measure say 5000 reads cumulative time, you'll get same problem again. Let's say you have more then one worker thread and multiple CPU's. Only then situation will be better. Perhaps you'll get somewhat better perfromance with OS context switch, but not to avail, it is humpered with same problem. You need more CPU-s and worker threads in order to service such large number of tasks. Just measure how much requests can be serviced in reasonable time and limit on that. For single cpu lock will be ok, but for multiple CPU's you have to somehow say Haskell to spawn multiple workers (more then one). I would be glad to know how to tell run time to use more then one worker thread. Greetings, Bane.

Thanks, Joel

-- http://wagerlabs.com/

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