On Wed, Feb 18, 2015 at 3:46 PM, David Ahern <[email protected]> wrote: > On 2/18/15 4:38 PM, Andi Kleen wrote: >> >> On Wed, Feb 18, 2015 at 04:33:31PM -0700, David Ahern wrote: >>> >>> On 2/18/15 11:30 AM, Andi Kleen wrote: >>> >>>>> I think Andi mentioned this to me last year -- that instruction >>>>> profiling was no longer reliable. >>>> >>>> >>>> It never was. >>> >>> >>> Why is that? What about profiling with other hardware counters? >> >> >> Practically all profiling has skid of some form. > > > ok, so you meant that only in the context of skid meaning the hit > instruction is off a few (ie., squint backwards at the annotate output). >
Thanks Andi and David, There's skid, but I was noticing what I thought was a different artifact in the profile: where only every 4th instruction is seen. Wouldn't this effect be more due to the IP pointing to the next instruction while a group of 4 are executed in parallel? Then there's skid on top of that.... Brendan -- To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
