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

Jump to bottom

runtime: convT2E called for function value #19335

Closed
cstockton opened this issue Mar 1, 2017 · 3 comments
Closed

runtime: convT2E called for function value #19335

cstockton opened this issue Mar 1, 2017 · 3 comments
Labels
FrozenDueToAge Performance
Milestone
Go1.9Maybe

Comments

@cstockton
Copy link

Go 1.8 amd64 linux when running the below program convT2E is called for BenchmarkEfaceFnVal but not for BenchmarkEfaceFn.

Program:

package main

import "testing"

func efaceFn(v interface{}) {
	return
}

func BenchmarkEfaceFnVal(b *testing.B) {
	b.ReportAllocs()

	efaceFnVal := efaceFn
	for i := 0; i < b.N; i++ {
		efaceFnVal(0x1)
	}
}

func BenchmarkEfaceFn(b *testing.B) {
	b.ReportAllocs()

	for i := 0; i < b.N; i++ {
		efaceFn(0x1)
	}
}

Result:

Name Iterations ns/op B/op allocs/op
BenchmarkEfaceFnVal-24 20000000 60.8 ns/op 8 B/op 1 allocs/op
BenchmarkEfaceFn-24 2000000000 0.48 ns/op 0 B/op 0 allocs/op
@bradfitz
Copy link
Contributor

bradfitz commented Mar 1, 2017

/cc @josharian @mdempsky @randall77

@bradfitz bradfitz added this to the Go1.9Maybe milestone Mar 1, 2017
@randall77
Copy link
Contributor

This is fixed at tip.

In BenchmarkEfaceFn, the call gets inlined and the conversion get compiled completely away.

In BenchmarkEfaceFnVal, the call still has to happen (we have no devirtualization of calls at the moment), but the conversion to interface now happens statically at compile time.

BenchmarkEfaceFnVal-8   	1000000000	         2.33 ns/op	       0 B/op	       0 allocs/op
BenchmarkEfaceFn-8      	2000000000	         0.52 ns/op	       0 B/op	       0 allocs/op

@cstockton
Copy link
Author

@randall77 Sorry I didn't check tip first, should have, thanks for the quick response

@golang golang locked and limited conversation to collaborators Mar 1, 2018
Sign up for free to subscribe to this conversation on GitHub. Already have an account? Sign in.
Assignees
No one assigned
Labels
FrozenDueToAge Performance
Projects
None yet
Milestone
Go1.9Maybe
Development

No branches or pull requests
4 participants
@bradfitz @cstockton @randall77 @gopherbot