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>
Functions `GetMounts()` and `parseMountTable()` return all the entries
as read and parsed from /proc/self/mountinfo. In many cases the caller
is only interested only one or a few entries, not all of them.
One good example is `Mounted()` function, which looks for a specific
entry only. Another example is `RecursiveUnmount()` which is only
interested in mount under a specific path.
This commit adds `filter` argument to `GetMounts()` to implement
two things:
1. filter out entries a caller is not interested in
2. stop processing if a caller is found what it wanted
`nil` can be passed to get a backward-compatible behavior, i.e. return
all the entries.
A few filters are implemented:
- `PrefixFilter`: filters out all entries not under `prefix`
- `SingleEntryFilter`: looks for a specific entry
Finally, `Mounted()` is modified to use `SingleEntryFilter()`, and
`RecursiveUnmount()` is using `PrefixFilter()`.
Unit tests are added to check filters are working.
[v2: ditch NoFilter, use nil]
[v3: ditch GetMountsFiltered()]
[v4: add unit test for filters]
[v5: switch to gotestyourself]
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Files that are suffixed with `_linux.go` or `_windows.go` are
already only built on Linux / Windows, so these build-tags
were redundant.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Fix the following warnings:
pkg/mount/mountinfo.go:5:6: type name will be used as mount.MountInfo by other packages, and that stutters; consider calling this Info
pkg/mount/mountinfo.go:7:2: struct field Id should be ID
Signed-off-by: Antonio Murdaca <runcom@linux.com>
