Re: [PATCH] mm, numa: Do not group on RO pages

From: Peter Zijlstra
Date: Fri Aug 02 2013 - 15:57:01 EST

> + /*
> + * Avoid grouping on DSO/COW pages in specific and RO pages
> + * in general, RO pages shouldn't hurt as much anyway since
> + * they can be in shared cache state.
> + */

OK, so that comment is crap. Its that you cannot work into RO pages and
this RO pages don't establish a collaboration.

> + if (page_mapcount(page) != 1 && !pmd_write(pmd))
> + flags |= TNF_NO_GROUP;

Rik also noted that mapcount == 1 will trivially not form groups. This
should indeed be so but I didn't test it without that clause.
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