mirror of
https://github.com/ceph/ceph-csi.git
synced 2024-11-23 14:50:24 +00:00
55 lines
1.9 KiB
Markdown
55 lines
1.9 KiB
Markdown
|
## pwalkdir: parallel implementation of filepath.WalkDir
|
||
|
|
|
||
|
|
This is a wrapper for [filepath.WalkDir](https://pkg.go.dev/path/filepath#WalkDir)
|
||
|
|
which may speed it up by calling multiple callback functions (WalkDirFunc)
|
||
|
|
in parallel, utilizing goroutines.
|
||
|
|
|
||
|
|
By default, it utilizes 2\*runtime.NumCPU() goroutines for callbacks.
|
||
|
|
This can be changed by using WalkN function which has the additional
|
||
|
|
parameter, specifying the number of goroutines (concurrency).
|
||
|
|
|
||
|
|
### pwalk vs pwalkdir
|
||
|
|
|
||
|
|
This package is very similar to
|
||
|
|
[pwalk](https://pkg.go.dev/github.com/opencontainers/selinux/pkg/pwalkdir),
|
||
|
|
but utilizes `filepath.WalkDir` (added to Go 1.16), which does not call stat(2)
|
||
|
|
on every entry and is therefore faster (up to 3x, depending on usage scenario).
|
||
|
|
|
||
|
|
Users who are OK with requiring Go 1.16+ should switch to this
|
||
|
|
implementation.
|
||
|
|
|
||
|
|
### Caveats
|
||
|
|
|
||
|
|
Please note the following limitations of this code:
|
||
|
|
|
||
|
|
* Unlike filepath.WalkDir, the order of calls is non-deterministic;
|
||
|
|
|
||
|
|
* Only primitive error handling is supported:
|
||
|
|
|
||
|
|
* fs.SkipDir is not supported;
|
||
|
|
|
||
|
|
* no errors are ever passed to WalkDirFunc;
|
||
|
|
|
||
|
|
* once any error is returned from any walkDirFunc instance, no more calls
|
||
|
|
to WalkDirFunc are made, and the error is returned to the caller of WalkDir;
|
||
|
|
|
||
|
|
* if more than one WalkDirFunc instance will return an error, only one
|
||
|
|
of such errors will be propagated to and returned by WalkDir, others
|
||
|
|
will be silently discarded.
|
||
|
|
|
||
|
|
### Documentation
|
||
|
|
|
||
|
|
For the official documentation, see
|
||
|
|
https://pkg.go.dev/github.com/opencontainers/selinux/pkg/pwalkdir
|
||
|
|
|
||
|
|
### Benchmarks
|
||
|
|
|
||
|
|
For a WalkDirFunc that consists solely of the return statement, this
|
||
|
|
implementation is about 15% slower than the standard library's
|
||
|
|
filepath.WalkDir.
|
||
|
|
|
||
|
|
Otherwise (if a WalkDirFunc is actually doing something) this is usually
|
||
|
|
faster, except when the WalkDirN(..., 1) is used. Run `go test -bench .`
|
||
|
|
to see how different operations can benefit from it, as well as how the
|
||
|
|
level of paralellism affects the speed.
|