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Visualize gc-events in UI

See original GitHub issue

From https://github.com/nearform/node-clinic-doctor/pull/42

@mcollina There is no visualization, you can look at the docs if you would like to see it. The problem with gc-stats is that it doesn’t expose all events. I just exposes some always and others only sometimes. It is a bit confusing. The trace_events shows all the events.

Using the trace_events is not currently possible because there I no way of synchronizing the trace_events clock with another clock. The V8 team is currently working on this: https://github.com/nodejs/node/issues/17349

Issue Analytics

State:
Created 6 years ago
Comments:11 (11 by maintainers)

Top GitHub Comments

1reaction

mcollinacommented, Jan 3, 2018

This is already implemented and it does not need a special build of V8, you should be able to implement it straight away.

0reactions

mcollinacommented, Aug 13, 2018

These events are interesting also for the CPU diagram, but I wouldn’t highlight there. Some of the spikes are caused by the GC. Il giorno lun 13 ago 2018 alle 15:08 Matteo Collina < matteo.collina@gmail.com> ha scritto:

I think the data about memory collected might be available somewhere. Il giorno lun 13 ago 2018 alle 12:56 Alan Slater notifications@github.com ha scritto:

Great, and I see it’s defined in format/trace-event-decoder.js.

They have start/finish times and durations but no data on amounts of memory recovered or equivalent - so presumably we’d just want to somehow:

a) highlight the time periods during which a GC event was in progess b) maybe also allow the user to see what type of GC event it was at any given point.

It looks like the possible types are:

‘V8.GCScavenger’ // appears to be by far the most common ‘V8.GCMarkSweepCompact’ // aggregated from GCFinalizeMC and GCIncrementalMarkingStart ‘V8.GCCompactor’ // is marked “purpose unknown” ‘V8.GCFinalizeMCReduceMemory’ // is marked “purpose unknown” ‘V8.GCPhantomHandleProcessingCallback’ // is marked “purpose unknown”

Are these GC event time intervals interesting/relevant to any charts other than Memory? For example I think they could be useful for understanding some event loop anomalies judging based on an earlier discussion with Dave.

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