Re: [9fans] thread STACK size

["Federico G. Benavento" <benavento@gmail.com>]

also if you're using bio(8) notice that a biobuf is >8kb

On Wed, May 19, 2010 at 6:20 AM, Sape Mullender
<sape@plan9.bell-labs.com> wrote:
>> A while ago, while working on btfs, I stumbled upon some sort of
>> overflow (http://9fans.net/archive/2009/07/77) which was in fact due
>> to the thread STACK being too small (and hence if I understood
>> correctly things would get written out of it, in the heap).
>> To be on the safe side, I have it set to 16384 now, but as I think I'm
>> getting near something usable with btfs, I'd like to go back to a more
>> fitting value. I think it's pretty important to have it as low as
>> possible since the number of threads/coroutines will grow linearly
>> with the number of peers connected (to be honest, I don't even know if
>> that can even scale in terms of memory use).
>>
>> So the question is, how can I evualuate what's the minimal value I can
>> set that to without getting into trouble again? Is there anything
>> smarter than just trial and error?
>
> There's no good way, really.  One thing you might do is change the thread
> library to initialize the stack to some pattern (zeroing it will probably
> do, but you can let your phantasy go wild here).  You can then, when your
> code has been running for a while, use acid -lthread and a bit of scripting
> to scan your stacks for the higest point where the pattern is disturbed.
>
>
> As a general rule in threaded programs, avoid declaring local arrays
> or large structs.  Instead, malloc them and free them when you're done.
> A file server, as an example, should never allocate an 8K message
> buffer on the stack.  If you can manage to obey the rule of not having
> arrays on the stack (as local variables), you can usually comfortably
> make use of 4K or 8K stacks.
>
>        Sape
>
>



-- 
Federico G. Benavento