Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged

On Tue, Jan 08, 2019 at 02:53:00PM +0100, Bernd Petrovitsch wrote:

On 08/01/2019 12:37, Jiri Kosina wrote:

quoted

On Tue, 8 Jan 2019, Bernd Petrovitsch wrote:

quoted

Shouldn't the application use e.g. mlock()/.... to guarantee no page 
faults in the first place?

Calling mincore() on pages you've just mlock()ed is sort of pointless 
though.

Obviously;-)

Sorry for being unclear above: If I want my application to
avoid suffering from page faults, I use simply mlock()
(and/or friends) to nail the relevant pages into physical
RAM and not "look if they are out, if yes, get them in" which
has also the risk that these important pages are too soon
evicted again.

Note, that mlock() doesn't prevent minor page faults. Mlocked memory is
still subject to mechanisms that makes the page temporary unmapped. For
instance migration (including NUMA balancing), compaction, khugepaged...

-- 
 Kirill A. Shutemov