pmap mmu optimization turned off on master (a week ago)
dillon at apollo.backplane.com
Mon Dec 10 09:08:35 PST 2012
We've turned off the machdep.pmap_mmu_optimize feature by default
on master. Note that it was never enabled (by default) for the 3.2
Currently there are two issues with the feature that need to be fixed.
These issues have cropped up in wider testing over the last month.
At the moment we do NOT recommend that anyone use this feature.
(1) There is a corruption issue somewhere which has yet to be found,
which shows up in rtorrent and apache.
(2) The pmap backing the VM objects which is used to provide the basis
for page table sharing might not be getting deallocated properly,
and is also not being garbage collected, and this *could* be
responsible for reports of bloated page 'wire' counts and lost
memory on machines over time.
These issues basically just require some bug work, I don't expect to
have to do any major reworking of the code so the feature WILL
definitely become standard at some point in 2013. But for now I
recommend that it not be used.
<dillon at backplane.com>
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