[Haskell-cafe] Threads with high CPU usage

[Peter Verswyvelen]

Would forkOS instead of forkIO help in this case?
On Sun, Dec 21, 2008 at 11:16 PM, Mads Lindstrøm
<mads_lindstroem at yahoo.dk>wrote:

> Hi Günter
>
> Günther Schmidt wrote:
> > Hi,
> >
> > in an application of mine I start a long-running operation in a thread
> via
> > forkIO so that the UI process doesn't get blocked.
> > It just so happens, that the long-running process also takes the CPU to
> > nearly 100% while it runs.
> >
> > During that time the run-time system does *not* switch back and forth
> > between the UI-process and the long-running task, it seems that the UI
> > process only gets woken up *after* the high CPU thread finishes
> completely.
> >
> > To the effect of course that it makes no difference at all to the UIs
> > responsiveness whether I use forkIO or not.
> >
> > The long running process is pretty atomic, it's a single query to the
> > database which takes up to a minute to complete so I don't see a chance
> to
> > squeeze a "mainIteration" in there.
>
> It could be the database library, as it may use unsafe foreign calls.
> Unsafe foreign calls blocks all other threads, even if you compile with
> the -threaded option. See
>
> http://www.haskell.org/ghc/docs/latest/html/libraries/base/Control-Concurrent.html#4.
>
> I cannot claim to know how all Haskell database libraries are
> implemented, but at least some of them use unsafe foreign calls. So
> which database library is you using?
>
> >
> > What can I do?
>
> If the problem has to do with unsafe foreign calls, then you can
> implement the database calls in a separate process. Not the easiest
> options, but I can think of no other.
>
> >
> > Günther
> >
>
> /Mads Lindstrøm
>
>
>
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