Bug 1741786 Comment 0 Edit History

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https://treeherder.mozilla.org/perfherder/compare?originalProject=mozilla-central&originalRevision=b16763f1da6bcf31f964744c765c4af480ae551c&newProject=try&newRevision=df12762eef9a5e7b6af281e8a94cbdc03313d066&framework=13&page=1&showOnlyComparable=1&showOnlyImportant=1

The comparison above is Browsertime tp6 microsoft, on Linux 18.04 x64 shippable build,
for revision `b16763f1da6bcf31f964744c765c4af480ae551c` both on `m-c` and `try`.
(`try` one has try commit, but its parent is `b16763f1da6bcf31f964744c765c4af480ae551c`)

The result shows 2-5% regression, with 21 runs, and the confidence is med to high.

It suggests that there's some difference in either:
  * the generated binary (maybe somewhere around PGO?)
     * at least I see several binary files are different between those 2 pushes.  haven't looked into the details how they're different tho
  * the test hardware

similar problem is reported before in bug 1515681, but that was about comparing `try` against recent `m-c` pushes,
and it's fixed by adding the following warning on perfherder
> It is not recommended to compare a try build against a mozilla-central build, unless it is based on latest mozilla-central.

This bus is about comparing the same revision built on `try` push and `m-c` push, so the above warning doesn't apply.

If there's actually some difference between the `try` push and `m-c` push, we should disallow comparing them, and show a message that suggests pushing the base revision also to `try`,
or at least reword the warning message on perfherder comparison page, and also show the warning on the comparison result page as well.
https://treeherder.mozilla.org/perfherder/compare?originalProject=mozilla-central&originalRevision=b16763f1da6bcf31f964744c765c4af480ae551c&newProject=try&newRevision=df12762eef9a5e7b6af281e8a94cbdc03313d066&framework=13&page=1&showOnlyComparable=1&showOnlyImportant=1

The comparison above is Browsertime tp6 microsoft, on Linux 18.04 x64 shippable build,
for revision `b16763f1da6bcf31f964744c765c4af480ae551c` both on `m-c` and `try`.
(`try` one has try commit, but its parent is `b16763f1da6bcf31f964744c765c4af480ae551c`)

The result shows 2-5% regression, with 21 runs, and the confidence is med to high.

It suggests that there's some difference in either:
  * the generated binary (maybe somewhere around PGO?)
     * at least I see several binary files are different between those 2 pushes.  haven't looked into the details how they're different tho
  * the test hardware

similar problem is reported before in bug 1515681, but that was about comparing `try` against recent `m-c` pushes,
and it's fixed by adding the following warning on perfherder
> It is not recommended to compare a try build against a mozilla-central build, unless it is based on latest mozilla-central.

This bug is about comparing the same revision built on `try` push and `m-c` push, so the above warning doesn't apply.

If there's actually some difference between the `try` push and `m-c` push, we should disallow comparing them, and show a message that suggests pushing the base revision also to `try`,
or at least reword the warning message on perfherder comparison page, and also show the warning on the comparison result page as well.

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