svn commit: r267858 - in head/sys/dev: virtio/balloon xen/balloon

[Attilio Rao]

On Wed, Jun 25, 2014 at 2:09 PM, Gleb Smirnoff <glebius at freebsd.org> wrote:
> On Wed, Jun 25, 2014 at 01:58:29PM +0200, Attilio Rao wrote:
> A> > Log:
> A> >   xen/virtio: fix balloon drivers to not mark pages as WIRED
> A> >
> A> >   Prevent the Xen and VirtIO balloon drivers from marking pages as
> A> >   wired. This prevents them from increasing the system wired page count,
> A> >   which can lead to mlock failing because of hitting the limit in
> A> >   vm.max_wired.
> A>
> A> This change is conceptually wrong.
> A> The pages balloon is allocating are unmanaged and they should be wired
> A> by definition. Alan and I are considering enforcing this (mandatory
> A> wired pages for unmanaged pages allocation) directly in the KPI.
> A> This in practice just seem an artifact to deal with scarce  wired
> A> memory limit. I suggest that for the XEN case this limit gets bumped
> A> rather relying on similar type of hacks.
>
> Proper limit would be to count pages wired by userland via mlock(2)
> and enforce limit only on those pages. Pages wired by kernel should
> be either unlimited or controled by a separate limit.

FWIW, I mostly agree with this. I think that the kernel and userland
limits should be split apart. But for the time being, rising the limit
is better.

Attilio


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