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

Branimir Maksimovic bmaxa at hotmail.com
Wed Dec 21 12:28:49 EST 2005

>From: Joel Reymont <joelr1 at gmail.com>
>To: "Branimir Maksimovic" <bmaxa at hotmail.com>
>CC: haskell-cafe at haskell.org
>Subject: Re: [Haskell-cafe] Killer pickler combinators (was Time leak)
>Date: Wed, 21 Dec 2005 14:51:42 +0000
>I'm not sure I buy this. Again, this helps:
>{-# NOINLINE lock #-}
>lock :: MVar ()
>lock = unsafePerformIO $ newMVar ()
>trace s = withMVar lock $ const $ putStrLn s
>and then in read_
>        cmd <- read h trace
>trace is called _after_ all the timings in read so it should not  affect 
>the timings.

It does not affects timings directly  , but indirectly.
You have putStrLn which performs some work and
that is point of serialization. Try no op instead of putStrLn and
you should get timeouts again.
i'm sure you'll get even better operation timings
if you lock around whole timing operation instead.
This will be valid only for single CPU only.
In this way you actually get same throughoutput,
with or without lock. It' just
you have to measure cummulative reads/sec which will be same
with/without lock for single CPU/worker thread.
Again, only way to improve performance is to use more then
one CPU/worker thread.

Greetings, Bane.

>You could basically say that the lock is at the end of read, after  all the 
>unpickling has been done. The other interesting thing is that  replacing 
>trace with
>delay _ = threadDelay 1
>does not solve the issue.
>On Dec 21, 2005, at 2:33 PM, Branimir Maksimovic wrote:
>>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.

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