Re: [Valgrind-users] instruction trace

[John R. <jr...@Bi...>]

David Brumley wrote:
 > [snip]
> I've used vtune to get instructions retired, but that is sort of on the
> "opposite" end of the processor that I'm interested in.  [snip]
 > For the paper, I'd like to compare instructions
> issued vs. instructions retired for the two programs.  On the P4, those
> two may not be the same for a number of weird P4 reasons (as I
> understand talking to P4 experts). [snip]
> I've tried valgrind with --single-step=yes, and see a couple of
> different things that I think *may* be the instructions issued, like
> "translate: new" in the output, but I'm not sure.  Is this instructions
> issued?

All x86 implementations beginning with the Intel PentiumPro [ca.1995] have
speculative, out-of-order execution, including along false conditional
control paths (and even false _un_conditional control paths).  Speculation
is influenced by code alignment, icache and dcache hits/misses, interrupts
and task switches, CPU temperature, etc.  "Instructions issued" is almost
meaningless for the hardware; certainly no software could ever compute it.

-- 
John Reiser, jr...@Bi...