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[S390] reference bit testing for unmapped pages 

On x86 a page without a mapper is by definition not referenced / old.
The s390 architecture keeps the reference bit in the storage key and
the current code will check the storage key for page without a mapper.
This leads to an interesting effect: the first time an s390 system
needs to write pages to swap it only finds referenced pages. This
causes a lot of pages to get added and written to the swap device.
To avoid this behaviour change page_referenced to query the storage
key only if there is a mapper of the page.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2011-07-24 10:47:59 +02:00
parent f433c4aec9
commit 50a15981a1
1 changed files with 3 additions and 3 deletions
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6
mm/rmap.c
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@ -869,11 +869,11 @@ int page_referenced(struct page *page,
vm_flags);
if (we_locked)
unlock_page(page);
if (page_test_and_clear_young(page_to_pfn(page)))
referenced++;
}
out:
if (page_test_and_clear_young(page_to_pfn(page)))
referenced++;
return referenced;
}