How to stop the thread from yielding per 20ms?

Ryan Yates fryguybob at
Sat Jul 4 14:08:42 UTC 2015

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.


On Sat, Jul 4, 2015 at 6:25 AM, Zhen Zhang <izgzhen at> 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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> ghc-devs at
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