commit edf8e6fef861d8c5ecc9e394b0146d6ebba57795
author Brad Fitzpatrick <bradfitz@golang.org> Mon Jul 18 00:47:35 2016 +0000
committer Brad Fitzpatrick <bradfitz@golang.org> Tue Jul 19 03:21:45 2016 +0000
tree 934328d1d711de4eb05df85c9750ce6c0f9d308e
parent caebc7a51c4e0f3abaf0f13fb8266d6e1a150d58

cmd/goimports, imports: optimize directory scanning and other things

This brings goimports from 160ms to 100ms on my laptop, and under 50ms
on my Linux machine.

Using cmd/trace, I noticed that filepath.Walk is inherently slow.
See https://golang.org/issue/16399 for details.

Instead, this CL introduces a new (private) filepath.Walk
implementation, optimized for speed and avoiding unnecessary work.

In addition to avoid an Lstat per file, it also reads directories
concurrently. The old goimports code did that too, but now that logic
is removed from goimports and the code is simplified.

This also adds some profiling command line flags to goimports that I
found useful.

Updates golang/go#16367 (goimports is slow)
Updates golang/go#16399 (filepath.Walk is slow)

Change-Id: I708d570cbaad3fa9ad75a12054f5a932ee159b84
Reviewed-on: https://go-review.googlesource.com/25001
Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>