Re: [PATCH] Hugepages should be accounted as unevictable pages.

From: Alok Kataria
Date: Tue Jun 23 2009 - 20:08:44 EST

On Tue, 2009-06-23 at 16:41 -0700, Dave Hansen wrote:
> On Tue, 2009-06-23 at 15:23 -0700, Alok Kataria wrote:
> > > Could you just teach the thing to which you are hinting that it also
> > > needs to go look in sysfs for huge page counts?
> >
> > :) yeah i could do that too...the point is that its a module and the
> > function to get the hugepages count is not exported right now. I could
> > very well add this as an exported symbol and use it from there, but
> > there can be someone who doesn't want symbols to be unnecessarily
> > exported if their is no in-tree modular usage of that symbol.
> Hmmm. So what is the module doing? The ol', "try to get as much memory
> as I possibly can" game? :)
> It sounds like you can get access to the vm statistics from existing
> exported symbols, but the stats don't give you quite the info that you
> need.

> So, you're trying to change things that you *can* get access to.

:) Not entirely, I thought that UNEVICTABLE by definition should
consider hugepages too.

> We do export all this stuff to userspace. We export all of the huge
> page sizes and how many pages are reserved, used, and allocated in each,
> plus the contentious Unevictable. Could you just do this calculation in
> userspace and pass it into the module with a modparam or sysfs file?

Hmm...lets see, I will look to moving that to userspace or something.

But irrespective of my need, we must clear the confusion around what
unevictable should actually mean.

I am biased towards getting hugepages accounted in that :), but what do
others think ?

Lee, I will let you take a decision on that, if the current semantics
look okay, it would be great if you could update the unevictable_lru
documentation about this being just the number of pages on

> -- Dave

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