Re: [Qemu-devel] [PATCH 6/6] coroutine: reduce stack size to 64kB

[Peter Lieven]

Am 01.07.2016 um 23:13 schrieb Richard Henderson:
> On 06/30/2016 12:37 AM, Peter Lieven wrote:
> > evaluation with the recently introduced maximum stack usage 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.
> >
> > Signed-off-by: Peter Lieven <address@hidden>
> > ---
> >  include/qemu/coroutine_int.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/qemu/coroutine_int.h b/include/qemu/coroutine_int.h
> > index eac323a..f84d777 100644
> > --- a/include/qemu/coroutine_int.h
> > +++ b/include/qemu/coroutine_int.h
> > @@ -28,7 +28,7 @@
> >  #include "qemu/queue.h"
> >  #include "qemu/coroutine.h"
> >
> > -#define COROUTINE_STACK_SIZE (1 << 20)
> > +#define COROUTINE_STACK_SIZE (1 << 16)
> >
> >  typedef enum {
> >      COROUTINE_YIELD = 1,
>
> Ought we check that this is not smaller than
>
>     sysconf(_SC_THREAD_STACK_MIN)
>
> which (for glibc at least), is 192k for ia64, 128k for aarch64, mips and tile 
> (though why it is quite so high in those later cases I don't know).

for x86_64 it seems to be 16k. I would not mind to adjust the stack size either 
in qemu_alloc_stack or change the macro for the coroutine stack
size into a function returning MAX(1 << 16, sysconf(_SC_THREAD_STACK_MIN)).

Peter