Kir Kolyshkin 96e23c4152 pkg/mount/mountinfo_linux: parser speed up ...

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`, when a linear search for '-' field,
when a split for the last 3 fields. The new code relies on a single
split.

I have also added more comments to aid in future development.

Finally, the test data is fixed to now have white space before the first field.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Upstream-commit: c611f18a7f16d8aa878a5a5c7537d23a0937c40a
Component: engine

2018-04-19 14:49:42 -07:00

..

engine

pkg/mount/mountinfo_linux: parser speed up

2018-04-19 14:49:42 -07:00