Re: [tarantool-patches] [PATCH 1/3] core/fiber: Increase default stack size

[Alexander Turenko <alexander.turenko@tarantool.org>]

On Wed, Mar 06, 2019 at 01:38:52AM +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 256K which should fit
> for common case. Later we will make this value configurable
> to address arbitrary stack sizes without a need to rebuild
> the 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
> ---
>  src/lib/core/fiber.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/src/lib/core/fiber.c b/src/lib/core/fiber.c
> index abd6c6b11..d4d16c05e 100644
> --- a/src/lib/core/fiber.c
> +++ b/src/lib/core/fiber.c
> @@ -92,10 +92,10 @@ static size_t page_size;
>  static int stack_direction;
>  
>  enum {
> -	/* The minimum allowable fiber stack size in bytes */
> -	FIBER_STACK_SIZE_MINIMAL = 16384,
> -	/* Default fiber stack size in bytes */
> -	FIBER_STACK_SIZE_DEFAULT = 65536
> +	/* The minimum allowable fiber stack size in 4K page */
> +	FIBER_STACK_SIZE_MINIMAL = 4 << 12,
> +	/* Default fiber stack size in 4K page */
> +	FIBER_STACK_SIZE_DEFAULT = 64 << 12,

I recently looked at #3564 and observed that 256 KiB of stack is not
enough for our http client (the wrapper around libcurl). I bisected how
much it requeres and found that it fails with 448 KiB, but succeeds with
480 KiB. I just tried the following case with different
FIBER_STACK_SIZE_DEFAULT constants on our tt-mac machine:

./src/tarantool <<< "print(require('json').encode(require('http.client').get('http://google.com')))"

Tarantool is linked to libcurl-7.61.0:

$ otool -L ./src/tarantool | grep libcurl
	/usr/local/opt/curl/lib/libcurl.4.dylib (compatibility version 10.0.0, current version 10.0.0)
$ strings /usr/local/opt/curl/lib/libcurl.4.dylib | grep libcurl/
libcurl/7.61.0

However this case succeeds on my Linux machine on tarantool with 64 KiB
stack with libcurl-7.63.0. Don't sure what is matter: libcurl version,
OS, some compilation or runtime options of libcurl. But at least we see
that there are environments where 256 KiB is not enough.

Maybe we should investigate what lead libcurl to use so much stack size
in that environment and possibly will find a way to configure it (at
runtime) to avoid this. Don't sure. So this message is just for the
record.

https://github.com/tarantool/tarantool/issues/3564

>  };
>  
>  /** Default fiber attributes */
> -- 
> 2.20.1
> 
>