[dm-devel] [PATCH 2/3] set pthread stack size to at least PTHREAD_STACK_MIN

[Hannes Reinecke]

Benjamin Marzinski wrote:
[ .. ]
> 
> This approach doesn't doesn't actually fix the bug that I see. The
> problem I was seeing is that setting the stacksize too small just causes
> pthread_attr_setstacksize() to fail, leaving you with the default stack
> size. On some architectures, the default stacksize is large, like 10Mb.
> Since you start one waiter thread per multipath device, every 100
> devices eats up 1Gb of memory. Your approach always uses the default
> stack size, unless it's too small.  I've never seen problems with the
> stack being too small. Only too large. Maybe your experience has been
> different.
> 
Me neither. Makes me wonder if we _really_ need to set the stacksize.
After all, I'm not aware that we're having any excessive stack usage
somewhere. Maybe we can simplify it by removing the stack attribute
setting altogether?

I'll see if I can get the different stacksizes and just compare them
to the 'updated' setting. Maybe there's no big difference after all...

> The other problem is that when I actually read the pthread_attr_init man
> page (it can fail. who knew?), I saw that it can fail with ENOMEM. Also,
> that it had a function to free it, and that the result of reinitializing
> an attr that hadn't been freed was undefined.  Clearly, this function
> wasn't intended to be called over and over without ever freeing the
> attr, which is how we've been using it in multipathd. So, in the spirit
> of writing code to the interface, instead of to how it appears to be
> currently implemented, how about this.
Hmm. You're not freeing the attribute for all non-logging threads neither.
Oversight? 

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
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