Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Specialize empty key value pairs #576

Merged
merged 1 commit into from
Oct 9, 2023

Conversation

EFanZh
Copy link
Contributor

@EFanZh EFanZh commented Aug 13, 2023

Currently, the __private_api::log function takes None::<&[(&str, _)]> as the kvs argument if no key-value pair is provided, but passing a None value may have some extra cost. We should be able to avoid this cost by encoding this information into a zero sized type (here I am using (), not sure if it is better to use a dedicated new type (such as struct EmptyKVs;)). Constructing a zero sized value is zero cost, which is less than constructing a None::<&[(&str, _)]>.

@EFanZh EFanZh force-pushed the specialize-empty-key-value-paris branch from 421a1aa to a814007 Compare August 13, 2023 16:46
@EFanZh EFanZh changed the title [WIP] Specialize empty key value pairs Specialize empty key value pairs Aug 13, 2023
@EFanZh EFanZh force-pushed the specialize-empty-key-value-paris branch from a814007 to ba272f9 Compare August 13, 2023 16:53
src/__private_api.rs Show resolved Hide resolved
@EFanZh EFanZh force-pushed the specialize-empty-key-value-paris branch 3 times, most recently from e05bce3 to db16ec8 Compare August 19, 2023 14:45
@EFanZh
Copy link
Contributor Author

EFanZh commented Aug 27, 2023

I have tested the effect on binary size of this PR on cargo-binstall, and this is the result:

opt-level lto codegen-units original size optimized size diff
3 off 1 13754440 13754440 0
3 off 16 16343208 16326824 -16384
3 thin 1 14520328 14520328 0
3 thin 16 17051784 17035400 -16384
3 fat 1 13152232 13152232 0
3 fat 16 14385128 14368744 -16384
"z" off 1 11247688 11251784 4096
"z" off 16 13197448 13172872 -24576
"z" thin 1 12144648 12136456 -8192
"z" thin 16 13488232 13488232 0
"z" fat 1 9662440 9658344 -4096
"z" fat 16 10113000 10100712 -12288

Aside from the (opt-level=z, lto=off, codegen-units=1) combination, all binary size changes are non-positive, you can reproduce the result using: https://github.com/EFanZh/log/tree/binary-size-test/cargo-binstall/test-binary-size.

I also tested the binary sizes with the instantiate_log_function function removed:

opt-level lto codegen-units original size optimized size diff
3 off 1 13754440 13754440 0
3 off 16 16343208 16326824 -16384
3 thin 1 14520328 14520328 0
3 thin 16 17051784 17035400 -16384
3 fat 1 13152232 13152232 0
3 fat 16 14385128 14368744 -16384
"z" off 1 11247688 11251784 4096
"z" off 16 13197448 13176968 -20480
"z" thin 1 12144648 12136456 -8192
"z" thin 16 13488232 13492328 4096
"z" fat 1 9662440 9658344 -4096
"z" fat 16 10113000 10100712 -12288

The binary sizes are mostly the same as the previous one, with the exception of (opt-level=z, lto=off, codegen-units=16) and (opt-level=z, lto=thin, codegen-units=16) combinations, whose effect become worse after removing the instantiate_log_function function.

I also tested the runtime performance with a hand written benchmark:

original  => cycles: 1115, instructions: 79, wall time: 322ns.
optimized => cycles: 954, instructions: 79, wall time: 323ns.

You can find the benchmark code here: https://github.com/EFanZh/log/tree/benchmark. I give up using criterion because the result changes significantly between runs, and I also often run into “took zero time” error. I also tried iai, but I get bheisler/iai#34 error. Finally I decided to use perf-event, since it is what the Rust language uses for its performance benchmark: https://github.com/rust-lang/rustc-perf/blob/master/collector/benchlib/src/measure/perf_counter/linux.rs.

@EFanZh EFanZh marked this pull request as ready for review August 27, 2023 15:32
Copy link
Contributor

@KodrAus KodrAus left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Thanks for investigating this @EFanZh! I think we should remove the instantiate_log_function item, but otherwise this looks good to me.

src/__private_api.rs Outdated Show resolved Hide resolved
@EFanZh EFanZh force-pushed the specialize-empty-key-value-paris branch from db16ec8 to b462186 Compare August 28, 2023 14:35
@EFanZh EFanZh requested a review from KodrAus September 10, 2023 04:54
@EFanZh
Copy link
Contributor Author

EFanZh commented Oct 1, 2023

Hi @KodrAus, is there anything I need to do to get this PR merged?

Copy link
Contributor

@KodrAus KodrAus left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Thanks for your patience on this one @EFanZh 🙇

This looks good to me.

@KodrAus KodrAus merged commit 87808fb into rust-lang:master Oct 9, 2023
14 checks passed
@EFanZh EFanZh deleted the specialize-empty-key-value-paris branch November 6, 2023 07:36
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
None yet
Projects
None yet
Development

Successfully merging this pull request may close these issues.

3 participants