[tarantool-patches] [rfc 3/4] core/fiber: Put static watermark into stack to track its usage

[Konstantin Osipov]

* Cyrill Gorcunov <gorcunov at gmail.com> [19/03/03 23:25]:
> We want to detect a situation where task in fiber is too eager for
> stack and close to its exhausting. For this sake upon stack creation
> we put 8 marks on last stack page with step of 128 bytes. Such params
> allows us to fill ~1/4 of a page, which does seem reasonable but
> we might change this params with time.
> 
> Since the watermark position is permanent and some task is close
> to stack limit we print about the situation once to not spam
> a user much and stop putting the mark on recycling.

> +	/*
> +	 * Initially we arm last page of a stack
> +	 * to catch if we're getting close to
> +	 * stack exhausting.
> +	 */
> +	if (stack_direction < 0)
> +		fiber->stack_wmark_ofl = fiber->stack;
> +	else
> +		fiber->stack_wmark_ofl = fiber->stack + fiber->stack_size - page_size;
> +	stack_put_wmark(fiber->stack_wmark_ofl);
> +}

Could you please incorporate some randomness when assigning this
address? A simple pseudo-random number within range 0
..page_size/2 would make me happy.


-- 
Konstantin Osipov, Moscow, Russia, +7 903 626 22 32
http://tarantool.io - www.twitter.com/kostja_osipov