Re: [regression v4.0-rc1] mm: IPIs from TLB flushes causing significant performance degradation.

Dave Chinner
2015-03-04T23:51:57Z

On Thu, Mar 05, 2015 at 12:35:45AM +0100, Ingo Molnar wrote:
>
> * Dave Chinner <david@fromorbit.com> wrote:
>
> > > After going through the series again, I did not spot why there is
> > > a difference. It's functionally similar and I would hate the
> > > theory that this is somehow hardware related due to the use of
> > > bits it takes action on.
> >
> > I doubt it's hardware related - I'm testing inside a VM, [...]
>
> That might be significant, I doubt Mel considered KVM's interpretation
> of pte details?

I did actaully mention that before:

| I am running a fake-numa=4 config on this test VM so it's got 4
| nodes of 4p/4GB RAM each.

but I think it got snipped before Mel was cc'd.

Perhaps size of the nodes is relevant, too, because the steady state
phase 3 memory usage is 5-6GB when this problem first shows up, and
then continues into phase 4 where memory usage grows again and peaks
at ~10GB....

Cheers,

Dave.