code review 4237055: testing: run GC before each benchmark run.

testing: run GC before each benchmark run.

[rog, 2011-03-03 18:32:35]

Hello r (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://go.googlecode.com/hg/

[r, 2011-03-03 18:34:08]

I think this is reasonable but would like a second opinion. (I know, I'm ugly.)

-rob

[rh, 2011-03-03 18:56:10]

http://codereview.appspot.com/4237055/diff/3001/src/pkg/testing/benchmark.go
File src/pkg/testing/benchmark.go (right):

http://codereview.appspot.com/4237055/diff/3001/src/pkg/testing/benchmark.go#...
src/pkg/testing/benchmark.go:69: runtime.GC()
Is it worth a small comment explaining why runtime.GC is called here?

[gri, 2011-03-03 19:02:07]

LGTM

I think it is reasonable to have the GC call. I haven't tried it but I would not
be surprised if it would lead to more consistent results (one test is not
influenced by the garbage created by another).

http://codereview.appspot.com/4237055/diff/3001/src/pkg/testing/benchmark.go
File src/pkg/testing/benchmark.go (right):

http://codereview.appspot.com/4237055/diff/3001/src/pkg/testing/benchmark.go#...
src/pkg/testing/benchmark.go:68: b.N = n
Just for better grouping of concerns:
Add a comment explaining the reason for the GC (try to get a comparable setup
for each runN), do the GC call, and then do all the b.-related stuff. (So,
comment, GC call, b.N = n, etc...)

[rog, 2011-03-03 19:11:20]

http://codereview.appspot.com/4237055/diff/3001/src/pkg/testing/benchmark.go
File src/pkg/testing/benchmark.go (right):

http://codereview.appspot.com/4237055/diff/3001/src/pkg/testing/benchmark.go#...
src/pkg/testing/benchmark.go:68: b.N = n
On 2011/03/03 19:02:07, gri wrote:
> Just for better grouping of concerns:
> Add a comment explaining the reason for the GC (try to get a comparable setup
> for each runN), do the GC call, and then do all the b.-related stuff. (So,
> comment, GC call, b.N = n, etc...)

Done.

http://codereview.appspot.com/4237055/diff/3001/src/pkg/testing/benchmark.go#...
src/pkg/testing/benchmark.go:69: runtime.GC()
On 2011/03/03 18:56:10, rh wrote:
> Is it worth a small comment explaining why runtime.GC is called here?

Done.

[rsc, 2011-03-03 19:19:00]

LGTM

[r, 2011-03-03 19:27:01]

*** Submitted as http://code.google.com/p/go/source/detail?r=10af7f44ea11 ***

testing: run GC before each benchmark run.

R=r, rh, gri, rsc
CC=golang-dev
http://codereview.appspot.com/4237055

Committer: Rob Pike <r@golang.org>