Closed Bug 1530057 Opened 5 years ago Closed 4 years ago

Disable Android LTO for non-PGO (opt) builds

Categories

(Firefox Build System :: General, defect)

Unspecified
Android
defect
Not set
normal

Tracking

(firefox-esr60 unaffected, firefox65 unaffected, firefox66 wontfix, firefox67 wontfix, firefox75 fixed)

RESOLVED FIXED
mozilla75
Tracking Status
firefox-esr60 --- unaffected
firefox65 --- unaffected
firefox66 --- wontfix
firefox67 --- wontfix
firefox75 --- fixed

People

(Reporter: cpeterson, Assigned: glandium)

References

Details

Attachments

(1 file)

Android LTO caused a 70-90% build time regression (WONTFIX'd bug 1483990). Developers want fast local builds and try runs, so we should disable LTO in non-shipping builds (i.e. non-PGO opt and debug).

Once we have Android PGO builds (bug 632954), we can disable LTO for opt builds. PGO would then imply LTO, like clang-cl did on Windows in bug 1475660.

Would we want to disable LTO for opt builds in all branches (autoland, inbound, central, and try) or just on autoland, inbound, and try? Is there value in building and testing opt with LTO in central in addition to opt without LTO on autoland and inbound? Any bugs we find in one of those configurations but not the other is most likely a compiler bug, not a Firefox bug. Do we care?

See Also: → 1530058

(In reply to Chris Peterson [:cpeterson] from comment #0)

Would we want to disable LTO for opt builds in all branches (autoland,
inbound, central, and try) or just on autoland, inbound, and try? Is there
value in building and testing opt with LTO in central in addition to opt
without LTO on autoland and inbound?

I would say that there's anti-value. :) Having different settings based on branch leads to unpleasant surprises, typically in the form of lost developer time in chasing down why something doesn't reproduce in one branch or the other.

Assuming that those PGO+LTO builds get their own full set of tests, I think it would be fine for "opt" to have neither PGO nor LTO on any branch.

Depends on: android-pgo-ARM64

LTO was enabled on Android back when the normal Android builds were the
ones we shipped. But now we have separate builds for what is shipped,
and they do PGO+LTO.

Assignee: nobody → mh+mozilla
Status: NEW → ASSIGNED
Blocks: 1615174
Pushed by mh@glandium.org:
https://hg.mozilla.org/integration/autoland/rev/1c3bdc899ec3
Disable LTO for non-PGO Android builds. r=froydnj
Status: ASSIGNED → RESOLVED
Closed: 4 years ago
Resolution: --- → FIXED
Target Milestone: --- → mozilla75
Regressions: 1617207

== Change summary for alert #24997 (as of Wed, 19 Feb 2020 09:38:27 GMT) ==

Improvements:

63% build times android-5-0-x86_64 asan taskcluster-c5d.4xlarge 2,085.51 -> 763.72

For up to date results, see: https://treeherder.mozilla.org/perf.html#/alerts?id=24997

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