ffcnt

Fast file counting and listing for spinning rust, in rust.

ffcnt's purpose is to provide a faster alternatives to some common filesystem operations as a frontend for the platter-walk crate.

• ffcnt --type f replaces find -type f | wc -l
• ffcnt --type f --ls --leaf-order content replaces find -type f and returns files in optimized order for reading
• ffcnt -s replaces du -s --apparent-size

Requirements

• Linux
• A filesystem that supports the fiemap ioctl on directories.
  Currently ext4 is known to provide that. If you know other ones, please report!
  Incompatible filesystems will work but gain no speedup over find.

You can test filesystem support with the filefrag tool.

```

supported

$ filefrag /tmp/ /tmp/: 3 extents found

unsupported

$ filefrag /mnt/test/ /mnt/test/: FIBMAP unsupported ```

Binary

You can find prebuilt x86_64-linux-glibc binaries without debug information under releases. For troubleshooting and other environments you'll have to build your own.

Build

• clone repo
• install liblzo2 and libz (build-time dependencies)
• install rust and cargo
• cargo build --release

Usage

``` fast file counting 0.3.0

USAGE: ffcnt [FLAGS] [OPTIONS] [dirs]...

FLAGS: -h, --help Prints help information --ls list files --prefetch attempt to prefetch directory indices from underlying mount device. requires read permission on device -s sum apparent length of matched files. Only counts hardlinked files once. Does not follow symlinks. Implies --leaf-order inode. -V, --version Prints version information

OPTIONS: --leaf-order optimize order for listing/stat/reads [values: inode, content, dentry] --type filter type [values: f, l, d, s, b, c, p]

ARGS: ... directories to traverse [default: cwd] ```

Unscientific Benchmark

Idle system:

``` $ echo 3 > /proc/sys/vm/drop_caches ; time find /tmp/foo/ -type f | wc -l 826536

real 0m52.289s user 0m0.680s sys 0m4.361s

$ echo 3 > /proc/sys/vm/drop_caches ; time ffcnt /tmp/foo/ --type f files: 826536

real 0m17.072s user 0m1.230s sys 0m2.190s

$ echo 3 > /proc/sys/vm/drop_caches ; time sudo ffcnt /tmp/foo/ --prefetch --type f files: 826536

real 0m13.311s user 0m2.029s sys 0m1.440s ```

Busy system with mixed read/write workload. Differences in file counts arose due to writes happening in the meantime:

```

echo 3 > /proc/sys/vm/drop_caches ; time ffcnt .

4411262

real 10m36.288s user 0m3.656s sys 0m7.588s

echo 3 > /proc/sys/vm/drop_caches ; time find . -type f | wc -l

4412101

real 45m54.955s user 0m3.212s sys 0m12.044s ```

Both tests were performed on HDDs with a directory structure of at least 2 nesting levels and a branching factor of 256

Ideas

• 1 thread per block device in tree