Re: [PATCH 1/3] lib/core/fiber: Increase default stack size

[Vladimir Davydov <vdavydov.dev@gmail.com>]

On Wed, Mar 13, 2019 at 01:47:19AM +0300, Cyrill Gorcunov wrote:
> The default 64K stack size used for years become too small
> for modern distors (Fedora 29 and etc) where third party libraries
> (such as ncurses) started to use 64K for own buffers and we get
> SIGSGV early without reaching interactive console phase.
> 
> Thus we increase default size up to 512K which should fit

May be, better use 1 MB, just to be sure?

> for common case. Later we will make this value configurable
> to address arbitrary stack sizes without a need to rebuild
> the whole code.
> 
> Note the values are switched to 4K page granularity for sake
> of future modifications -- we gonna manipulate pages to
> relax rss usage if OS allows.
> 
> Closes #3418

Should be "Part of #3418". We use "Closes" only with the last patch in
the series (it makes GitHub close the issue).

> ---
>  src/lib/core/fiber.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/src/lib/core/fiber.c b/src/lib/core/fiber.c
> index abd6c6b11..f16ac873f 100644
> --- a/src/lib/core/fiber.c
> +++ b/src/lib/core/fiber.c
> @@ -93,9 +93,9 @@ static int stack_direction;
>  
>  enum {
>  	/* The minimum allowable fiber stack size in bytes */
> -	FIBER_STACK_SIZE_MINIMAL = 16384,
> +	FIBER_STACK_SIZE_MINIMAL = 4 << 12,
>  	/* Default fiber stack size in bytes */
> -	FIBER_STACK_SIZE_DEFAULT = 65536
> +	FIBER_STACK_SIZE_DEFAULT = 128 << 12

I don't like using '<< 12' for stack sizes. Why 12? Because the page
size is typically 4K. I wouldn't count on that - it's userspace so it
looks confusing.