Nick Piggin writes:
 > 

[...]

 > 
 > But by clearing the referenced bit when below the reclaim_mapped
 > threshold, you're throwing this information away.
 > 
 > Say you have 16 mapped pages on the active list, 8 referenced, 8 not.
 > You do a !reclaim_mapped scan. Your 16 pages are now in the same
 > order and none are referenced. You now do a reclaim_mapped scan and
 > reclaim 8 pages. 4 of them were the referenced ones, 4 were not.
 > 
 > With my change, you would reclaim all 8 non referenced pages.

Which is wrong, because none of them was referenced _recently_. These
pages are cold, according to the VM's notion of hotness. (Long time
probably has passed between !reclaim_mapped and reclaim_mapped scans in
your example.)

It seems correct to make deactivation decision on the basic of recent
accesses to the page rather than by checking whether page was ever
accessed.

 > 

Nikita.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"aart@kvack.org"> aart@kvack.org </a>