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SubjectRe: [RFC PATCH 0/3] Fix ebizzy performance regression on IvyBridge due to X86 TLB range flush

* Mel Gorman <> wrote:

> > [...]
> >
> > stddev appears to be rather large especially around a client count
> > of 7-8. It will be difficult to fine-tune the TLB range flush
> > constants if noise is too large.
> The number of iterations were very low to have high confidence of
> the figures. The high standard deviation for 5 clients was a single
> large outlier. It potentially could be stabilised to some extent by
> bumping up the number of iterations a lot and using percentiles
> instead of means.

Fair enough - and you were bisecting so length of runtime and
confidence of detection were obviously the primary concerns.

> I'm a bit wary of optimising the TLB flush ranges based on the
> benchmark even if we stabilised the figures. [...]

Absolutely - but they do appear to be pretty 'adversarial' to the TLB
optimization, with a measurable slowdown in a pretty complex,
real-life workload pattern.

So future tuning efforts will have to take such workloads into effect
as well, to make sure we don't regress again.



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