Value Clips memory usage grows with the square of the number of "times" entries

[marktucker]

Description of Issue

If you create a value clip with 15000 "times" entries, the Usd_Clip data structures consume about 5GB of data, regardless of the size of the data in the actual clip files.

This memory if consumed by the fact that each Usd_Clip object makes a copy of the 15000-entry timeMapping array created in the Usd_ClipSet constructor. I think each Usd_Clip applies the same sorting procedure to the data, and makes it's own copy. Seems like the obvious solution would be to have the Usd_ClipSet constructor massage the data, then pass a shared pointer to each Usd_Clip constructor. I'd be happy to make a PR for this if you think this is the correct approach to fixing this.

Steps to Reproduce

1. Unzip the attached file:
   value_clip_memory.zip
2. Load the box_loop.usd file into usdview. Memory usage will be 5-6GB, even though this is just a box flipping back and forth between two positions.

Package Versions

Tested in 20.08, 21.08, and 21.11

[jilliene]

Filed as internal issue #USD-7222

[spiffmon]

Hey @marktucker - oof, we've never exercised the explicit form to that scale; good find! Your approach seems to us like the right thing, and we'd be happy to get a PR.

[LucaScheller]

Hey @jilliene / @spiffmon,
hope you are doing well!

We (at RISE | Visual Effects Studios) were wondering what the current state of the attached PR from Mark is? Has it been reviewed/are there plans to merge it soon (#1777)? Thanks again Mark for submitting the PR :)

We've been running into this issue quite often for heavy FX scenes, the fix would help us quite a bit if it gets released soon :)

Cheers,
Luca

[spiffmon]

Hi @LucaScheller , although it hasn't been pushed out to gitHub yet, I believe we merged the PR just last week, so it will be in the dev branch soon, and in the next release, tentatively 22.08

[LucaScheller]

Thanks for the update, that's great to hear :)

[sunyab]

PR #1777 was merged and released in 22.08, closing this out. Thanks!