Re: [PATCH] mm/swap: add function get_total_swap_pages to expose total_swap_pages

[Michal Hocko]

On Tue 30-01-18 02:56:51, He, Roger wrote:
> Hi Michal:
> 
> We need a API to tell TTM module the system totally has how many swap
> cache.  Then TTM module can use it to restrict how many the swap cache
> it can use to prevent triggering OOM.  For Now we set the threshold of
> swap size TTM used as 1/2 * total size and leave the rest for others
> use.

Why do you so much memory? Are you going to use TB of memory on large
systems? What about memory hotplug when the memory is added/released?
 
> But get_nr_swap_pages is the only API we can accessed from other
> module now.  It can't cover the case of the dynamic swap size
> increment.  I mean: user can use "swapon" to enable new swap file or
> swap disk dynamically or "swapoff" to disable swap space.

Exactly. Your scaling configuration based on get_nr_swap_pages or the
available memory simply sounds wrong.
-- 
Michal Hocko
SUSE Labs