I've been asked to give a talk on performance to a University Computing
department.

I know the z hardware has in builtin instrumentation which allows you to
see where the delays were for a particular instruction.  For example this
load instruction got data from the L3 cache and it took x nano seconds.

Is there a presentation on this?

I remember seeing a presentation (it may have been IBM confidential)
showing that a Load could be slow, if the data was in a the cache in a book
3 ft away, compared to it being in the cache on the chip.
Also the second time round a loop is faster than the first time because the
instructions are in the instruction cache.

This was all mind blowing stuff!

Colin

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