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>
