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As it turns out, the Rust compiler uses variable length LEB128 encoded
integers internally. It so happens that they spent a fair amount of
effort micro-optimizing the decoding functionality [0] [1], as it's in
the hot path.
With this change we replace our decoding routines with these optimized
ones. To make that happen more easily (and to gain some base line speed
up), also remove the "shift" return from the respective methods. As a
result of these changes, we see a respectable speed up:
Before:
test util::tests::bench_u64_leb128_reading ... bench: 128 ns/iter (+/- 10)
After:
test util::tests::bench_u64_leb128_reading ... bench: 103 ns/iter (+/- 5)
Gsym decoding, which uses these routines, improved as follows:
main/symbolize_gsym_multi_no_setup
time: [146.26 µs 146.69 µs 147.18 µs]
change: [−7.2075% −5.7106% −4.4870%] (p = 0.00 < 0.02)
Performance has improved.
[0] rust-lang/rust#69050
[1] rust-lang/rust#69157
Signed-off-by: Daniel Müller <deso@posteo.net>
Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## main #719 +/- ##
==========================================
+ Coverage 94.62% 94.65% +0.03%
==========================================
Files 49 49
Lines 9466 9486 +20
==========================================
+ Hits 8957 8979 +22
+ Misses 509 507 -2 ☔ View full report in Codecov by Sentry. |
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As it turns out, the Rust compiler uses variable length LEB128 encoded integers internally. It so happens that they spent a fair amount of effort micro-optimizing the decoding functionality [0] [1], as it's in the hot path.
With this change we replace our decoding routines with these optimized ones. To make that happen more easily (and to gain some base line speed up), also remove the "shift" return from the respective methods. As a result of these changes, we see a repsectable speed up:
Before:
After:
Gsym decoding, which uses these routines, improved as follows:
[0] rust-lang/rust#69050
[1] rust-lang/rust#69157