perf(runtime): optimize Deno.file open & stream

[littledivy]

Opening and closing files is 2.5x faster

# Deno new
open_file_sync     7.55 µs/iter     (7.51 µs … 7.72 µs)   7.56 µs   7.72 µs   7.72 µs
# Deno `main`
open_file_sync    18.31 µs/iter   (17.79 µs … 39.75 µs)  18.25 µs  19.62 µs  20.62 µs

ext/flash send_file benchmark now gives 7GB/s transfer rate. 1.3x faster than main:

Transfer/sec:      5.79GB # main
Transfer/sec:      7.56GB # new

[littledivy]

something to note: ReadableStream initialization triggers a pretty serious deopt in V8. From a flamegraph of the send file server on main:

[aapoalas]

Opening and closing files is 2.5x faster

# Deno `main`
open_file_sync     7.55 µs/iter     (7.51 µs … 7.72 µs)   7.56 µs   7.72 µs   7.72 µs
# Deno new
open_file_sync    18.31 µs/iter   (17.79 µs … 39.75 µs)  18.25 µs  19.62 µs  20.62 µs

Am I reading this wrong somehow? I read this as the new open_file_sync taking 18 microseconds and the old one taking only 7.5 microseconds, ie. old one being faster.

[littledivy]

Am I reading this wrong somehow? I read this as the new open_file_sync taking 18 microseconds and the old one taking only 7.5 microseconds, ie. old one being faster.

Oopsie, wrong labels.

[bartlomieju]

LGTM