code review 5316048: xml: Benchmarks for unmarshaling of large arrays

xml: Benchmarks for unmarshaling of large arrays I proposed these to rsc@golang.org when they originally exposed a performance problem in R60. (Performance appeared to be dominated by stack grow/shrink operations). The problem appears to have been fixed, but I still think these provide a realistic use case.

[rochberg_go, 2011-10-25 19:44:50]

Hello golang-dev@googlegroups.com (cc: golang-dev@googlegroups.com, rsc@golang.org), I'd like you to review this change to https://go.googlecode.com/hg/

[rsc, 2011-10-31 15:44:44]

http://codereview.appspot.com/5316048/diff/4001/src/pkg/xml/marshal_test.go File src/pkg/xml/marshal_test.go (right): http://codereview.appspot.com/5316048/diff/4001/src/pkg/xml/marshal_test.go#n... src/pkg/xml/marshal_test.go:451: buf := buildSpaceshipBuffer(b) Using N to control the size of the array is not going to give a reliable result, because the time does not scale linearly with N (at some point you start swapping, garbage collecting more, etc). It would be better to pick a fixed size, build the string the first time you get called, and then run the benchmark b.N times.

[rochberg_go, 2011-11-23 03:23:32]

This is back from the beyond. PTAL

[r, 2011-11-23 16:56:53]

http://codereview.appspot.com/5316048/diff/10002/src/pkg/encoding/xml/marshal... File src/pkg/encoding/xml/marshal_test.go (right): http://codereview.appspot.com/5316048/diff/10002/src/pkg/encoding/xml/marshal... src/pkg/encoding/xml/marshal_test.go:429: func init() { this is for benchmarks, not the package at large, so it should be done only if we're running benchmarks. i suggest moving this code into a function that returns the buffer, and either remembering the value or just calculating it again the second time. then in the benchmarks, suspend the timer while you build the buffer. lots of examples like this to look at in other packages.

[rochberg_go, 2011-11-25 17:07:45]

Sure. Done.

[rochberg_go, 2011-12-21 21:36:59]

On 2011/11/25 17:07:45, rochberg_go wrote: > Sure. Done. ping