452235 - Need better tracking of memory through Sampling API

Status: VERIFIED FIXED

(Tamarin Graveyard :: Virtual Machine, defect)

Description

[Erik Tierney]

Attachment: Implements sampling of all allocs/deallocs

The sampling API only provides tracking of allocs/deallocs of AvmPlusScriptableObjects.  This misses a lot of allocs that the VM makes internally, so the numbers you get from the Sampling API don't account for a lot of the memory TC is using.

Comment 1

[Erik Tierney]

The patch includes better sampling, and also changes to make the sampler work in Release mode.

Comment 2

[Tommy Reilly]

Comment on attachment 335528 [details] [diff] [review]
Implements sampling of all allocs/deallocs

We should have an inlined check for whether sampling is enabled in GC::Alloc and in GCAlloc::Finalize. Don't want to pay the cost of a call if sampling is disable.

We should also benchmark and profile a pure allocation test (call new Object() from a loop) to make sure haven't introduced any additional release build overhead.

I see FEATURE_SAMPLER and MEMORY_SAMPLER CPP symbols, can we reduce to one?

Comment 3

[Erik Tierney]

Attachment: Patch with changes from comments

Added mmgc flag to quickly check if we are sampling - if we are, then go through slow function calls/thread local access, etc.  Should be no penalty when not sampling.
Changed MEMORY_SAMPLER to FEATURE_SAMPLER, now is only defined in MMgc.h.

Comment 4

[Erik Tierney]

Change has been pushed

Comment 5

[Chris Peyer]

Resolved fixed engineering / work item that has been pushed.  Setting status to verified.