Messages in this thread | | | From | Michael Neuling <> | Subject | Invalid perf_branch_entry.to entries question | Date | Tue, 07 May 2013 11:35:28 +1000 |
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Peter & Stephane,
We are plumbing the POWER8 Branch History Rolling Buffer (BHRB) into struct perf_branch_entry.
Sometimes on POWER8 we may not be able to fill out the "to" address. We initially thought of just making this 0, but it's feasible that this could be a valid address to branch to.
The other logical value to indicate an invalid entry would be all 1s which is not possible (on POWER at least).
Do you guys have a preference as to what we should use as an invalid entry? This would have some consequences for the userspace tool also.
The alternative would be to add a flag alongside mispred/predicted to indicate the validity of the "to" address.
Mikey
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