os: make windows Stat as fast as Lstat for files and directories
Recent CL 41834 made windows Stat work for all symlinks.
But CL 41834 also made Stat slow.
John Starks sugested
(see https://github.com/golang/go/issues/19922#issuecomment-
300031421)
to use GetFileAttributesEx for files and directories instead.
This makes Stat as fast as at go1.9.
I see these improvements on my Windows 7
name old time/op new time/op delta
StatDot 26.5µs ± 1% 20.6µs ± 2% -22.37% (p=0.000 n=9+10)
StatFile 22.8µs ± 2% 6.2µs ± 1% -72.69% (p=0.000 n=10+10)
StatDir 21.0µs ± 2% 6.1µs ± 3% -71.12% (p=0.000 n=10+9)
LstatDot 20.1µs ± 1% 20.7µs ± 6% +3.37% (p=0.000 n=9+10)
LstatFile 6.23µs ± 1% 6.36µs ± 8% ~ (p=0.587 n=9+10)
LstatDir 6.10µs ± 0% 6.14µs ± 4% ~ (p=0.590 n=9+10)
and on my Windows XP
name old time/op new time/op delta
StatDot-2 20.6µs ± 0% 10.8µs ± 0% -47.44% (p=0.000 n=10+10)
StatFile-2 20.2µs ± 0% 7.9µs ± 0% -60.91% (p=0.000 n=8+10)
StatDir-2 19.3µs ± 0% 7.6µs ± 0% -60.51% (p=0.000 n=10+9)
LstatDot-2 10.8µs ± 0% 10.8µs ± 0% -0.48% (p=0.000 n=10+8)
LstatFile-2 7.83µs ± 0% 7.83µs ± 0% ~ (p=0.844 n=10+8)
LstatDir-2 7.59µs ± 0% 7.56µs ± 0% -0.46% (p=0.000 n=10+10)
Updates #19922
Change-Id: Ice1fb5825defb05c79bab4dec0692e0fd1bcfcd5
Reviewed-on: https://go-review.googlesource.com/43071
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>