Hi!
I did some tests with the new Upstream/Asyncify feature (ie. "Bysyncify")
on the Doom 3 port.
I am using Chrome 75/Ubuntu 18.04/nVidia binary drivers, and used the
"timedemo demo1" command to measure the FPS (not available on the D3 demo
though, too bad. I had to do this with the full version of the game).
The good news: UPSTREAM/ASYNCIFY is working well! And easier to use than
Emterpreter. However there is a catch on the final wasm size. Here are the
raw results:
TARGET FPS SIZE (MB)
O2/FASTCOMP/EMTERPRETER 50 4,55 MB (for reference. NB: I
am using whitelisting feature on EMTERPRETER)
O2/UPSTREAM/ASYNCIFY 50 6,81 MB
O2/UPSTREAM (no Asyncify) 50 3,90 MB
O3/UPSTREAM/ASYNCIFY 51 6,96 MB
Os/UPSTREAM/ASYNCIFY 41 5,56 MB
Oz/UPSTREAM/ASYNCIFY 40 5,56 MB
What to read from these numbers:
- Performance
-- FASTCOMP/EMTERPRETER and UPSTREAM/ASYNCIFY have a similar performance
profile: with O2 optimization, there 50 FPS on average for both targets.
-- ASYNCIFY have no impact on performance: with O2 optimization, there is
50 FPS on average with and without for both targets (NB: on the D3 port, I
really tried to 'yield' as few as possible)
-- There is however an important gap between Os/Oz and O2/O3: using Os lead
to a 20% performance hit comparted to O2 (50 FPS with O2/O3 => 40 FPS with
Os/Oz)
-- O3 compared to O2 does not bring significant performance improvement
-- Same thing for Oz compared to Os: both are almost the same
- Binary size
-- UPSTREAM/ASYNCIFY do have a big impact on final binary size: this
roughly a +50% increase (from 4,55 MB with O2/FASTCOMP/EMTERPRETER => 6,81
MB with O2/UPSTREAM/ASYNCIFY)
-- It is really the ASYNCIFY that cause this binary size increase, as
without ASYNCIFY, UPSTREAM produce a binary that is 15% smaller than
FASTCOMP (from 4,55 MB with FASTCOMP/EMTERPRETER => 3,90 MB with UPSTREAM)
-- Using Os compared to O2 brings a binary size improvement (from 6,81 MB
with O2 => 5,56 MB with Os), but this does not match with FASTCOMP (4,55
MB)
-- Oz compared to Os does not bring significant binary size improvement
So, all in all, my observation is that ASYNCIFY works well, but the binary
size increase is not negligible (+50%).
Using Os/Oz instead of O2/O3 allow to reduce that overhead to some extent,
but it is at the expense of a 20% performance hit (at least on the D3
port), and not on par with the FASTCOMP binary size.
As it appears it is really the Asyncify transformation that brings the
binary size increase, the whitelisting feature could really bring the best
of both world:
- By default (that is, without whitelisting):
- Ease of use of ASYNCIFY compared to EMTERPRETER (this works *by
default*, without having to do some extra work)
- No performance impact of using ASYNCIFY (at least, when using
yield/sleep carefully)
- Cons: +50% binary size
- With whitelisting:
- The binary size issue could be mitigated a lot, as UPSTREAM give
smaller binary size than FASTCOMP (-15% on D3)
- Cons: obviously, some work to do with whitelisting, but this is the
same as with EMTERPRETER
Here it is!
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