Closed Bug 719492 Opened 8 years ago Closed 8 years ago

Telemetry for time spent in between GCs


(Core :: JavaScript Engine, defect)

Not set





(Reporter: mccr8, Assigned: billm)



(Whiteboard: [Snappy:P2])


(1 file)

This could help us find scheduling regressions.
Whiteboard: [Snappy]
Bill said he'd do this as part of his incremental GC stuff, as he's already computing things like what % of the time is in the GC.
Assignee: general → wmccloskey
And actually, that undersells what he is already computing a bit.  Here's his comment about what he is computing:

 * MMU (minimum mutator utilization) is a measure of how much garbage collection
 * is affecting the responsiveness of the system. MMU measurements are given
 * with respect to a certain window size. If we report MMU(50ms) = 80%, then
 * that means that, for any 50ms window of time, at least 80% of the window is
 * devoted to the mutator. In other words, the GC is running for at most 20% of
 * the window, or 10ms. The GC can run multiple slices during the 50ms window
 * as long as the total time it spends is at most 10ms.

It looks like he is currently computing MMU(20ms) and MMU(50ms).
Attached patch patchSplinter Review
Here's a patch on top of the incremental GC stuff. I only added MMU(50ms). Our MMU for smaller window sizes is pretty bad even in testing, so it's probably not worth reporting right now.
Attachment #591675 - Flags: review?(continuation)
Comment on attachment 591675 [details] [diff] [review]

Review of attachment 591675 [details] [diff] [review]:

Attachment #591675 - Flags: review?(continuation) → review+
Whiteboard: [Snappy] → [Snappy:P2]
This was r+ 3 weeks ago. Who can land these new probes?
The patch is based on incremental GC, so it can't land yet. However, I realize that besides the MMU measurement, it would be nice just to know how many seconds ago the last GC was. So maybe I'll do a separate patch for that. It could land right away.
Looks like this landed with incremental GC, so I'm marking as fixed.
Closed: 8 years ago
Depends on: IncrementalGC
Resolution: --- → FIXED
The target milestone isn't set. Did this land in time for 12 or 13?
Target Milestone: --- → mozilla13
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