Closed Bug 1815170 Opened 2 years ago Closed 1 year ago

Consider turning off the Spectre mitigation for C++ calls

Categories

(Core :: JavaScript Engine: JIT, task)

task

Tracking

()

RESOLVED DUPLICATE of bug 1837602

People

(Reporter: jandem, Assigned: jandem)

References

(Blocks 2 open bugs)

Details

(Whiteboard: [sp3])

The LFENCE we emit after a call into C++ is relatively expensive. It was always a pretty big hammer for a more theoretical Spectre issue through C++ code. It might make sense to disable this one by default now that we're shipping Fission on desktop and are getting closer to disabling all of our mitigations in isolated content processes anyway.

I think the next step here is to measure the actual performance overhead on the full benchmarks, because I do think this one tends to affect micro-benchmarks more.

1% sounds like a good enough justification to me. Is there anything else that we want to know or think about before doing this?

Flags: needinfo?(jdemooij)

We discussed this a bit more. There's good progress on fixing the remaining blockers for disabling mitigations in Fission content processes, so let's just wait for that. If that work ends up taking longer than expected we can reconsider this.

Status: ASSIGNED → RESOLVED
Closed: 2 years ago
Flags: needinfo?(jdemooij)
Resolution: --- → WONTFIX
Whiteboard: [sp3]

That work has ended up taking longer than I expected. Can we reconsider this?

Flags: needinfo?(jdemooij)
See Also: → 1438886

As per Jeff's proposal let's re-open. It feels to me like we shouldn't let this linger longer than needed.

Status: RESOLVED → REOPENED
Resolution: WONTFIX → ---

(In reply to Jeff Muizelaar [:jrmuizel] from comment #5)

That work has ended up taking longer than I expected. Can we reconsider this?

We talked about this a bit. The ORB work is progressing well, changes have landed, and they're now waiting for telemetry results. Let's hold off for a few more weeks until we have more information on that effort. It sounds like we should have more information on that soon, but I'll leave the needinfo to check on this.

Status: REOPENED → RESOLVED
Closed: 2 years ago1 year ago
Duplicate of bug: 1837602
Flags: needinfo?(jdemooij)
Resolution: --- → DUPLICATE
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