[PATCH] D140063: [AutoFDO] Use getHeadSamplesEstimate instead of getTotalSamples to compute profile callsite staleness

[Lei Wang via Phabricator via llvm-commits]

wlei added a comment.

In D140063#3998253 <https://reviews.llvm.org/D140063#3998253>, @wenlei wrote:

> I thought the idea is to compute the % of samples being dropped due to mismatch? in this case, all samples from callsite will be dropped, so I actually don't see a problem with using getTotalSamples. Yes you can argue that they can be merged with base profile, but then that argument applies to getHeadSamplesEstimate too?

Yeah, it's tricky to quantify the dropped callsite samples's impact. I was thinking in a reversed way, if we use `getTotalSamples`, I feel like the total samples are completely dropped(not merged into top-level profile), in fact it's still in use. And for `getHeadSamplesEstimate`, I feel it's like only the callsite call/jump's samples are dropped, but I admit that this's also not accurate, the missing inlining from big total samples could affect more on perf. I don't have strong opinion on this.


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https://reviews.llvm.org/D140063