Subj : Re: dynamic allocation, deallocation but not heap fragmentation!
To   : comp.programming.threads
From : David Schwartz
Date : Sat May 14 2005 12:04 pm


"jimjim" <netuser@blueyonder.co.uk> wrote in message 
news:fRkhe.31770$G8.20390@text.news.blueyonder.co.uk...

> Or, did you mean I can have a fixed number of threads and queue up somehow 
> client requests? How can I choose how many threads I need in this way?

    It's not difficult to compute the number of threads. You need:

    1) One thread for each CPU you need to keep busy.

    2) One thread for each quick I/O that must be blocking that you can 
usefully do at the same time. (This is typically 5 or 6.)

    3) One thread for each long-term I/O that must be blocking. (You usually 
don't have any of these, but sometimes you can't avoid it.)

    4) One thread for each special job that really needs its own thread. 
(For example, one thread to wait for signals, maybe one thread to kick off 
timed events, and so on.)

    And that's it, unless I forgot something.

    So when a client makes a request, add it to a linked list of requests 
and signal a condition variable. When a thread has nothing else to do, it 
pulls the head request off the linked list or blocks on the condition 
variable if there are no requests. You can dynamically adjust the number of 
threads if you really need to.

    DS

.