On Wed, Dec 19, 2012 at 02:01:19AM -0500, Simon Jeons wrote:

On Mon, 2012-12-17 at 13:12 -0500, Johannes Weiner wrote:

quoted

When ex-KSM pages are faulted from swap cache, the fault handler is
not capable of re-establishing anon_vma-spanning KSM pages.  In this
case, a copy of the page is created instead, just like during a COW
break.

These freshly made copies are known to be exclusive to the faulting
VMA and there is no reason to go look for this page in parent and
sibling processes during rmap operations.

Use page_add_new_anon_rmap() for these copies.  This also puts them on
the proper LRU lists and marks them SwapBacked, so we can get rid of
doing this ad-hoc in the KSM copy code.

Is it just a code cleanup instead of reduce rmap overhead?

Both.

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