why do we call clear_active_flags in shrink_inactive_list ?

why do we call clear_active_flags in shrink_inactive_list ?

[minchan Kim]

In 2.6.23's shrink_inactive_list function, why do we have to call
clear_active_flags after isolate_lru_pages call ?
IMHO, If it call isolate_lru_pages with "zone->inactive_list", It can
be sure that it is not PG_active. So I think It is unnecessary calling
clear_active_flags. Nonetheless, Why do we have to recheck PG_active
flags wich clear_active_flags.

If it is right, which case it happens that page is set to be PG_active ?

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Thanks,
barrios

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Re: why do we call clear_active_flags in shrink_inactive_list ?

[Rik van Riel]

On Sun, 30 Dec 2007 16:32:42 +0900
"minchan Kim" <barrioskmc@gmail.com> wrote:

> In 2.6.23's shrink_inactive_list function, why do we have to call
> clear_active_flags after isolate_lru_pages call ?
> IMHO, If it call isolate_lru_pages with "zone->inactive_list", It can
> be sure that it is not PG_active. 

If we call isolate_lru_pages with mode = ISOLATE_BOTH, then it
can return both active and inactive pages and the calling function
has to be able to deal with both kinds of pages.

ISOLATE_BOTH is used when the kernel is trying to defragment memory,
for larger physically contiguous allocations.

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