Re: [PATCH v6] add MAP_UNLOCKED mmap flag

From: Gleb Natapov
Date: Tue Jan 19 2010 - 05:41:32 EST

On Tue, Jan 19, 2010 at 10:44:23AM +0200, Pekka Enberg wrote:
> On Tue, Jan 19, 2010 at 10:26 AM, Gleb Natapov <gleb@xxxxxxxxxx> wrote:
> >> me that you're trying to use a big hammer (mlock) when a polite hint
> >> for the VM would probably be sufficient for it do its job.
> >>
> > I what to tell to VM "swap this, don't swap that" and as far as I see
> > there is no other way to do it currently.
> Yeah, which is why I was suggesting that maybe posix_madvise() needs
> to be extended to have a MADV_NEED_BUT_LESS_IMPORTANT flag that can be
> used as a hint by mm/vmscan.c to first swap the guest address spaces.
If such thing would exist may be I would have used it since swapping out
of a wrong page is not live or death matter in my case, but mlockall()
provides me with exactly what I need and without swapping out wrong
pages. Speaking about adding such madvise call wouldn't it be even
harder to justify? It obviously not good enough for real-time use and my
case, I admit, is unusual. Also if we start prioritise memory why stop
on binary, why not set value like "this memory is more important then
that memory by factor of 5"?

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