Re: [PATCH RFC/RFB] x86_64, i386: interrupt dispatch changes

[Matt Mackall <mpm@selenic.com>]

On Mon, 2008-11-10 at 21:00 -0800, H. Peter Anvin wrote:
> Okay, after spending most of the day trying to get something that isn't
> completely like white noise (interesting problem, otherwise I'd have
> given up long ago) I did, eventually, come up with something that looks
> like it's significant.  I did a set of multiple runs, and am looking for
> the "waterfall points" in the cumulative statistics.
> 
> http://www.zytor.com/~hpa/baseline-hpa-3000-3600.pdf
> 
> This particular set of data points was gathered on a 64-bit kernel, so I
> didn't try the segment technique.
> 
> It looks to me that the collection of red lines is enough to the left of
> the black ones that one can assume there is a significant effect,
> probably by about a cache miss worth of time.

This graph is a little confusing. Is the area under each curve here
supposed to be a constant?

Is this latency from all interrupts as seen by userspace? Or does a
particular interrupt dominate?

-- 
Mathematics is the supreme nostalgia of our time.