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Date: Thu, 5 Mar 2015 10:51:26 +1100
From: Dave Chinner <david@fromorbit.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Matt B <jackdachef@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>, xfs@oss.sgi.com
Subject: Re: [regression v4.0-rc1] mm: IPIs from TLB flushes causing
 significant performance degradation.
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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.
-- 
Dave Chinner
david@fromorbit.com