2003305 - fromBase64 is very slow

Status: NEW

(Core :: JavaScript Engine, task, P3)

Description

[Denis Palmeiro [:denispal]]

Go to https://simdutf.github.io/browserbase64/ and run the benchmark.

Firefox:
~3083.30 MiB/s

Chrome:
~7060.66 MiB/s

Safari:
~11336.78 MiB/s

We were even worse before, but bug 1994067 and bug 1995626 improved performance by about 10x. However, we are 2-3x behind.

Comment 1

[Markus Stange [:mstange]]

Profile: https://share.firefox.dev/4ajW3kw

I see two things:

1. The CPU work of decoding and storing the bytes is where most of the time (78%) is spent.
2. We decode into a temporary buffer and do a copy rather than adopting the buffer into the typed array.

The copy seems worth avoiding. TypedArray::fromLength also has the cost of zeroing the allocated buffer, which is unnecessary since we're going to overwrite all of it. Edit: Ah, André had already filed bug 1996197 about the copy, nice.