The mountinfo parser implemented via `fmt.Sscanf()` is slower than the one
using `strings.Split()` and `strconv.Atoi()`. This rewrite helps to speed it
up to a factor of 8x, here is a result from `go bench`:
> BenchmarkParsingScanf-4 300 22294112 ns/op
> BenchmarkParsingSplit-4 3000 2780703 ns/op
I tried other approaches, such as using `fmt.Sscanf()` for the first
three (integer) fields and `strings.Split()` for the rest, but it slows
things down considerably:
> BenchmarkParsingMixed-4 1000 8827058 ns/op
Note the old code uses `fmt.Sscanf` first, then a linear search for the
'-' field, then a split for the last 3 fields. The new code relies
on a single split.
One other thing is, the new code is more future proof as it skips
extra optional fields before the separator (currently there are none).
I have also added more comments to aid in future development.
Finally, the test data is fixed to not have white space before
the first field.
Based on a similar change in Moby,
https://github.com/moby/moby/pull/36091
[v2: remove no-op break statement to silence staticcheck]
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This moves both the Mount type and mountinfo into a single mount
package.
This also opens up the root of the repo to hold the containerd client
implementation.
Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
