[tarantool-patches] Re: [RFC] fiber: Increase default stack size

[Cyrill Gorcunov <gorcunov@gmail.com>]

On Fri, Feb 22, 2019 at 12:24:12PM +0300, Георгий Кириченко wrote:
> > 
> > I somehow fail to see how it is different from the current scheme.
> > In the patch we put single 8 16 bytes poison at 64K (well, page
> > aligned offset to be precise) and once the fiber scheduled out we
> > test it. I suspect the difference you mean is to _when_ test the poison?
> > Or you mean to poison the whole 64K?
>
> I complain only that you check poison on each fiber schedule what could be too 
> expensive - a fiber could be scheduled about million times per second.
> I think If we would check a fiber stack poison when it goes to recycle so is 
> will be a better option.

Sounds reasonable. Will take a look, thanks! Still we should take into
account that the stack of a fiber (for our regular fibers) won't exceed
1M thus will be covered by 2M pmd entry and expensive part is a cache
line refill only. Initially I thought if I could simply test for
poison just once when fiber is sched'ing out but then realised that
a task can easily wipe poison out on later sched cycles.