Re: [PATCH] perf: Add a new sort order: SORT_INCLUSIVE (v4)
From: Arun Sharma
Date: Tue Mar 27 2012 - 14:10:13 EST
On 3/24/12 7:14 PM, Frederic Weisbecker wrote:
The other problem in branch stacks/LBR is that they're
sampled branches. Just because I got a sample with:
a -> b
b -> c
doesn't necessarily mean that the callchain was a -> b -> c.
Not sure what you mean. If you have a -> b, b -> c in single
LBR sample it means you got a -> b -> c.
I was going by Stephane's commit message here:
> Statistical sampling of taken branch should not be confused
> for branch tracing. Not all branches are necessarily captured
Stephane, could you please explain if the 16 filtered branches in LBR
are guaranteed to be from a given callchain to the leaf function? My
understanding is that it's not.
callchain1: a -> b -> d -> e (sample a->b)
callchain2: a -> c -> b -> f (sample b->f)
on PMU interrupt can we end up with:
b -> f <- top of stack
a -> b
even though a -> b -> f can never happen in the actual program flow?
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