Re: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19

Ingo Molnar
2005-11-01T19:02:49Z

* Rob Landley <rob@landley.net> wrote:

> On Tuesday 01 November 2005 08:46, Ingo Molnar wrote:
> > how will the 100% solution handle a simple kmalloc()-ed kernel buffer,
> > that is pinned down, and to/from which live pointers may exist? That
> > alone can prevent RAM from being removable.
>
> Would you like to apply your "100% or nothing" argument to the virtual
> memory management subsystem and see how it sounds in that context?
> (As an argument that we shouldn't _have_ one?)

that would be comparing apples to oranges. There is a big difference
between "VM failures under high load", and "failure of VM functionality
for no user-visible reason". The fragmentation problem here has nothing
to do with pathological workloads. It has to do with 'unlucky'
allocation patterns that pin down RAM areas which thus become
non-removable. The RAM module will be non-removable for no user-visible
reason. Possible under zero load, and with lots of free RAM otherwise.

Ingo