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Issue 670062 link

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Status: Untriaged
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Pri: 3
Type: Bug

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issue 669505


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speed-bisect


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Bisect - Make output on rollbacks more obvious.

Project Member Reported by simonhatch@chromium.org, Nov 30 2016

Issue description

From https://bugs.chromium.org/p/chromium/issues/detail?id=669505

In this case you'd expect the bisect to step in V8 and narrow down the commit range further, which didn't happen because the v8 roll was a rollback. The bisect script grabs the v8 commit message and marks that as the culprit which is wrong.

I'd suggest in this case to check the DEPS revisions are in order, if not specify clearly in the output that this was a rollback and stepping into the range isn't possible.
 
Cc: machenb...@chromium.org
Recording relevant comments from machenbach:  crbug.com/669505 



Ah right. Then this is simple. Also the graphs have recovered:
https://chromeperf.appspot.com/report?sid=abee31cc6ef51ddd123a049fc235d39b212b63290cc5d50466bc43d94845ef88&rev=433138

1. V8 made an improvement.
2. V8 was rolled back behind the improvement for the branch (flagged here as regression).
3. After the branch V8 rolled forward and the improvement got in again.

This is basically wontfix, you can mark it as such. I keep it open for minor remarks:


1. Bisect actually dived in one step and reported in comment 3:
https://chromium.googlesource.com/v8/v8/+/bdd3886218dfe76e8560eb8a18401942452ae859
instead of
https://chromium.googlesource.com/chromium/src/+/b3028836333034e1bffde377a017d3026069ec6e
The latter one, at least as additional information would have been helpful.

2. The link in comment 3 resolves to chromium/src instead of v8/v8 which must be adjusted manually.
Blocking: 669505
Components: Speed>Bisection

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