Messages in this thread |  | | Date | Thu, 26 Apr 2001 15:17:38 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: [patch] swap-speedup-2.4.3-B3 (fwd) |
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On Thu, 26 Apr 2001, Linus Torvalds wrote: > > On the other hand, to offset some of these, we actually count the page > accessed _twice_ sometimes: we count it on lookup, and we count it when we > see the accessed bit in vmscan.c. Which results in some pages getting aged > up twice for just one access if we go through the vmscan logic, while if > we just map and unmap them they get counted just once.
And sometimes three times, if you count the PAGE_AGE_START bonus points you get whenever your age is found to be 0 (or less than PAGE_AGE_START). I think I see the idea, but seems more voodoo.
If you're looking to _simplify_ in this area, there's a confusing host (9) of intercoupled age-up-and-down de/activate functions. Aren't those better decoupled? i.e. the ageing ones ageonly, the de/activate ones not messing with age at all.
Then I think you're left with just age_page_up() and age_page_down() (maybe inlines as below, assuming the PAGE_AGE_START voodoo), plus activate_page(), deactivate_page() and deactivate_page_nolock().
static inline void age_page_up(struct page *page) { page->age += PAGE_AGE_ADV; if (page->age > PAGE_AGE_MAX) page->age = PAGE_AGE_MAX; else if (page->age < PAGE_AGE_START + PAGE_AGE_ADV) page->age = PAGE_AGE_START + PAGE_AGE_ADV; }
static inline void age_page_down(struct page *page) { page->age >>= 1; }
But this is no more than tidying, don't let me distract you.
Hugh
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