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

[Peter Lieven <pl@kamp.de>]

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 <pl@kamp.de>
>> ---
>>  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