Re: Hot/cold allocation -- swsusp can not handle hot pages

[William Lee Irwin III]

On Sat, Nov 02, 2002 at 07:19:00PM +0100, Pavel Machek wrote:
> Swsusp counts free pages, and relies on fact that when it allocates
> page there's one free page less. That is no longer true with hot
> pages.
> I attempted to work it around but it seems I am getting hot pages even
> when I ask for cold one. This seems to fix it. Does it looks like
> "possibly mergable" patch?
> --- clean/mm/page_alloc.c	2002-11-01 00:37:44.000000000 +0100
> +++ linux-swsusp/mm/page_alloc.c	2002-11-01 22:53:47.000000000 +0100
> @@ -361,7 +361,7 @@
>  	unsigned long flags;
>  	struct page *page = NULL;
>  
> -	if (order == 0) {
> +	if ((order == 0) && !cold) {
>  		struct per_cpu_pages *pcp;
>  
>  		pcp = &zone->pageset[get_cpu()].pcp[cold];
> 

This doesn't seem to be doing what you want, even if it seems to work.
If you want there to be one free page less, then allocating it will
work regardless. What are you looking for besides that? If it's not
already working you want some additional semantics. Could this involve
is_head_of_free_region()? That should be solvable with a per-cpu list
shootdown algorithm to fully merge all the buddy bitmap things.

Bill