Messages in this thread |  | | Date | Fri, 13 Dec 2013 14:35:17 +0100 | From | Ingo Molnar <> | Subject | Re: [RFC PATCH 0/3] Fix ebizzy performance regression on IvyBridge due to X86 TLB range flush |
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* Mel Gorman <mgorman@suse.de> 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.
Thanks,
Ingo
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