Messages in this thread |  | | | Date | Thu, 10 Aug 2006 15:23:10 +0000 (GMT) | | From | moreau francis <> | | Subject | Re : Re : sparsemem usage |
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KAMEZAWA Hiroyuki wrote: > On Thu, 10 Aug 2006 14:46:01 +0000 (GMT) > moreau francis <francis_moreau2000@yahoo.fr> wrote: >> Why not implementing page_exist() by simply using mem_map[] ? When >> allocating mem_map[], we can just fill it with a special value. And >> then when registering memory area, we clear this special value with >> the "reserved" value. Hence for flatmem model, we can have: >> >> #define page_exist(pfn) (mem_map[pfn] != SPECIAL_VALUE) >> > putting a special value to a page struct at mem_map + pfn ?
yes
> >> and it should work for sparsemem too and other models that will use >> mem_map[]. >> >> Another point, is page_exist() going to replace page_valid() ? > what is page_valid() here ? pfn_valid() (in current kernel) ?
sorry I was meaning pfn_valid() instead of page_valid() in the whole email.
> >> I mean page_exist() is going to be something more accurate than >> page_valid(). All tests on page_valid() _only_ will be fine to test >> page_exist(). But all tests such: >> >> if (page_valid(x) && page_is_ram(x)) >> >> can be replaced by >> >> if (page_exist(x)) >> >> So, again, why not simply improving page_valid() definition rather >> than introduce a new service ? >>
s/page_valid/pfn_valid
> I welcome to do that if implementation is sane. > pfn_valid() --- check there is a page struct > page_exist() --- check there is a physical memory. >
new definition of pfn_valid() would be "a physical page exists". And this definition imply the old one "it's safe to read the page struct *"
> but discussing without patch is not very good. please post your patch. > Then we can discuss more concrete things. >
Since I'm not kernel hacker, or rather a newbie one, I try to make sure that it worth to dig in that direction before working hard to write a patch.
thanks
Francis
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