How to stop the thread from yielding per 20ms?

[Takenobu Tani]

Hi Zhen,

Although you might be resolved, there are some information.

In your example code, threads are waiting a MVar for each IO(print).
(thread switch by self yield rather than timer-based(preemptive)
scheduling)

Maybe, these information would be helpful.

    Parallel and Concurrent Programming in Haskell
    Chapter 7. Basic Concurrency: Threads and MVars
    http://chimera.labs.oreilly.com/books/1230000000929/ch07.html

    The GHC scheduler
    http://blog.ezyang.com/2013/01/the-ghc-scheduler/

    Runtime Support for Multicore Haskell

http://research.microsoft.com/en-us/um/people/simonpj/papers/parallel/multicore-ghc.pdf

    Extending the Haskell Foreign Function Interface with Concurrency
    http://community.haskell.org/~simonmar/papers/conc-ffi.pdf

And, ThreadScope and eventlog are here.

    Parallel and Concurrent Programming in Haskell
    15. Debugging, Tuning, and Interfacing with Foreign Code
    Event Logging and ThreadScope

http://chimera.labs.oreilly.com/books/1230000000929/ch15.html#sec_conc_eventlogging

    ThreadScope
    https://wiki.haskell.org/ThreadScope


So, few image.

http://takenobu-hs.github.io/downloads/haskell_ghc_illustrated.pdf#page=82

http://takenobu-hs.github.io/downloads/haskell_ghc_illustrated.pdf#page=47


Cheers,
Takenobu


2015-07-05 14:10 GMT+09:00 Zhen Zhang <izgzhen at gmail.com>:

> Hi Ryan,
>
> Thank for your help. But it turned out to be not working for me. I even
> commented out the `startTimer` and `stopTimer` in `rts/Timer.c`, but it
> seems not working as well.
>
> For example. this program:
>
> main = do
> forkIO $ forever $ print “a”
> forkIO $ forever $ print “b”
> threadDelay 100000
>
> When I added the `-threaded`, it will schedule normally, despite whether I
> commented out some code or add `-V0`. When I dropped  `-threaded`, the
> `timerManager` stopped working as well, so it doesn’t make sense to me. Bad
> luck, but thank you all the way.
>
> Zhen
>
> --
> Zhen Zhang
> USTC, China
>
> On July 4, 2015 at 10:08:44 PM, Ryan Yates (fryguybob at gmail.com) wrote:
>
> Hi Zhen,
>
> The RTS flag -V sets the tick interval (setting to 0 disables).  If you
> grep for `RtsFlags.MiscFlags.tickInterval` you can find where it gets
> used.  Hope this helps.
>
> Ryan
>
> On Sat, Jul 4, 2015 at 6:25 AM, Zhen Zhang <izgzhen at gmail.com> wrote:
>
>>  Hi,
>>
>>  I am trying to stop the GHC thread scheduler from atomically do
>> round-robin scheduling. It might be strange that I am asking for that, in
>> fact, my intention is to implement the “Lightweight Concurrency” on top of
>> current RTS system. I am trying to use `GHC.Event`’s timeout mechanism to
>> interfere with the scheduling behavior and it seems working a bit. But the
>> automatic scheduling at the same time by RTS renders this effort invalid.
>>
>>  For this part, I have tried to modify `rts/Scheduler.c`, masked some
>> `startTimer` in `schedule()`, change the `appendToQueue` to `pushOnQueue`
>> in `scheduleHandleYield` but nothing really works. (The GHC is still doing
>> RR scheduling, even I changed some key code I thought)
>>
>>  So I am curious if anyone familiar with the RTS could give me some
>> suggestions on this problem.
>>
>> Thanks a lot!
>>
>> Zhen
>>
>>
>>
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>>
>
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