RE: [patch] mm, thp: count thp_fault_fallback anytime thp faultfails

From: David Rientjes
Date: Wed Aug 21 2013 - 18:16:59 EST


On Wed, 21 Aug 2013, Kirill A. Shutemov wrote:

> David Rientjes wrote:
> > Currently, thp_fault_fallback in vmstat only gets incremented if a
> > hugepage allocation fails. If current's memcg hits its limit or the page
> > fault handler returns an error, it is incorrectly accounted as a
> > successful thp_fault_alloc.
> >
> > Count thp_fault_fallback anytime the page fault handler falls back to
> > using regular pages and only count thp_fault_alloc when a hugepage has
> > actually been faulted.
> >
> > Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
>
> It's probably a good idea, but please make the behaviour consistent in
> do_huge_pmd_wp_page() and collapse path, otherwise it doesn't make sense.
>

The collapse path has no fallback, the allocation either succeeds or it
fails.
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