Re: [Qemu-devel] [PATCH 03/15] coroutine-ucontext: reduce stack size to 64kB

[Dr. David Alan Gilbert]

* Paolo Bonzini (address@hidden) wrote:
> 
> 
> On 28/06/2016 11:01, Peter Lieven wrote:
> > evaluation with the recently introduced maximum stack size monitoring 
> > revealed
> > that the actual used stack size was never above 4kB so allocating 1MB stack
> > for each coroutine is a lot of wasted memory. So reduce the stack size to
> > 64kB which should still give enough head room.
> 
> If we make the stack this much smaller, there is a non-zero chance of
> smashing it.  You must add a guard page if you do this (actually more
> than one because QEMU will happily have stack frames as big as 16 KB).
> The stack counts for RSS but it's not actually allocated memory, so why
> does it matter?

I think I'd be interested in seeing the /proc/.../smaps before and after this
change to see if anything is visible and if we can see the difference
in rss etc.

Dave

> 
> Paolo
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK