Re: [PATCH 1/6] CKRM: Basic changes to the core kernel

[Dave Hansen <haveblue@us.ibm.com>]

>  static inline void
>  add_page_to_active_list(struct zone *zone, struct page *page)
>  {
>         list_add(&page->lru, &zone->active_list);
>         zone->nr_active++;
> +       ckrm_mem_inc_active(page);
>  }

Are any of the current zone statistics used any more when this is
compiled in?

Also, why does everything have to say ckrm_* on it?  What if somebody
else comes along and wants to use the same functions to do some other
kind of accounting? 

I think names like this are plenty long and descriptive enough:

        mem_inc_active(page);
        clear_page_class(page);
        set_page_class(...);
        
I'd drop the "ckrm_".
        
> +#define PG_ckrm_account                21      /* CKRM accounting */

Are you sure you really need this bit *and* a whole new pointer in
'struct page'?  We already do some tricks with ->mapping so that we can
tell what is stored in it.  You could easily do something with the low
bit of your new structure member.

> @@ -355,6 +356,7 @@ free_pages_bulk(struct zone *zone, int c
>                 /* have to delete it as __free_pages_bulk list manipulates */
>                 list_del(&page->lru);
>                 __free_pages_bulk(page, zone, order);
> +               ckrm_clear_page_class(page);
>                 ret++;
>         }
>         spin_unlock_irqrestore(&zone->lock, flags);

When your option is on, how costly is the addition of code, here?  How
much does it hurt the microbenchmarks?  How much larger does it
make .text?

> +       if (!in_interrupt() && !ckrm_class_limit_ok(ckrm_get_mem_class(p)))
> +               return NULL;

ckrm_class_limit_ok() is called later on in the same hot path, and
there's a for loop in there over each zone.  How expensive is this on
SGI's machines?  What about an 8-node x44[05]?  Why can't you call it
from interrupts?

-- Dave

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