Would forkOS instead of forkIO help in this case?
On Sun, Dec 21, 2008 at 11:16 PM, Mads Lindstrøm
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-Concurren....
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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