[Haskell-cafe] Slow mvar when compiled with threaded

[Bob Ippolito]

I haven't yet been able to sort out the performance difference, and
probably won't have time to dig in deeper with profiling tools today. I've
put together a gist with all of the files and a cabal file so it's easy to
build with the right options.

https://gist.github.com/etrepum/8312165


On Tue, Jan 7, 2014 at 7:47 PM, Bob Ippolito <bob at redivi.com> wrote:

>
>
> On Tuesday, January 7, 2014, Branimir Maksimovic wrote:
>
>>  On 01/08/2014 04:15 AM, Bob Ippolito wrote:
>>
>> On Tuesday, January 7, 2014, Branimir Maksimovic wrote:
>>
>>> On 01/07/2014 09:39 PM, Bob Ippolito wrote:
>>>
>>>> Here's a much simpler implementation for that sort of pattern, using
>>>> channels to fan out work to threads. I added a dependency on Criterion
>>>> because getCPUTime is basically useless for this kind of measurement on Mac
>>>> OS X since it doesn't include the time that the process spent waiting on IO:
>>>>
>>> Great, thank you very much. You gave me material for learning ;)
>>> However, my version is significantly faster when compiling without
>>> -threaded.
>>> With -threaded option, your version is much faster than mine, but both
>>> are significantly slower
>>> then compile without -threaded.
>>>
>>
>>  Happy to look into it, I didn't have time today to do benchmarks
>> (and Mac OS X is the worst platform to do this kind of testing on
>> regardless of language, its network stack is inconsistent at best). I need
>> to know more:
>>
>>  How exactly are you compiling?
>>
>>
>> ghc-7.6.3 --make -O2 client.hs
>>
>>  Which OS?
>>
>>
>> Ubuntu 13.10 with 3.13-rc7 kernel.
>>
>>  What version of GHC and Haskell Platform?
>>
>>
>> bmaxa at maxa:~$ apt-cache policy haskell-platform
>> haskell-platform:
>>   Installed: 2013.2.0.0
>>   Candidate: 2013.2.0.0
>>   Version table:
>>  *** 2013.2.0.0 0
>>         500 http://archive.ubuntu.com/ubuntu/ saucy/universe amd64
>> Packages
>>         100 /var/lib/dpkg/status
>>
>>
>>  What is the exact command line you execute it with?
>>
>>
>> time ./client maxa 5055 1000 100000
>>
>
> What happens if you add +RTS -N to the end of that command line?
>
>
>>
>>
>>  What timings do you get?
>>
>> with your version:
>> real    0m4.235s
>> user    0m1.589s
>> sys    0m2.642s
>>
>> with my version
>> real    0m3.010s
>> user    0m0.590s
>> sys    0m2.417s
>> that is, of course, without -threaded
>>
>>  What's the code for the server are you connecting to?
>>
>> import Network (listenOn,PortID(..))
>> import Network.Socket (accept,close)
>> import Network.Socket.ByteString
>> import System.Environment
>> import Control.Concurrent (forkIO)
>>
>> main = do
>>     n <- getArgs
>>     let nn = (read.head) n :: Int
>>     putStrLn $ "Listening on " ++ show nn
>>     sock <- listenOn $ PortNumber $ fromIntegral nn
>>     serve sock
>>
>> serve sock = do
>>     (s,_) <- accept sock
>>     forkIO $ process s
>>     serve sock
>>
>> process sock = do
>>     buf <- recv sock 1024
>>     sendAll sock buf
>>     close sock
>>
>>  Loopback, local network, or internet?
>>
>>
>> loopback. Testing is on same computer.
>>
>> Thanks!
>>
>
> Great, I'll look closer later tonight or tomorrow morning.
>
>
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