Add a summary line of the ZFS Compressed ARC to top(1)

[allanjude]

Summary

This provides details about the compression of cached ZFS data

Example output:
CPU: 0.1% user, 0.0% nice, 0.0% system, 0.0% interrupt, 99.9% idle
Mem: 72M Active, 13G Inact, 30G Wired, 81G Free
ARC: 20G Total, 12G MFU, 6304M MRU, 1853K Anon, 369M Header, 1685M Other
_ 17G Compressed, 36G Uncompressed, 1.81:1 Ratio, 1238M Overhead
Swap: 4096M Total, 4096M Free

The compression ratio is logical_size / actual_size.

Sponsored By: FreeBSD Storage Summit

[bcr]

No comments about the actual change other than I really want to see this going into the tree. Thanks for working on it.

[allanjude]

I considered putting it behind a flag, but, decided against it.

[jpaetzel]

LGTM

[smh]

Some may find it useful if it was bit shorter, currently its 82 chars in the example.

May be change "Compressed ARC:" to just "ARC:" as the detail gives whats compressed and whats not?

Edit: Or not as I just spotted the line above is already just ARC :(

[allanjude]

In D9829#202940, @smh wrote:

Some may find it useful if it was bit shorter, currently its 82 chars in the example.

May be change "Compressed ARC:" to just "ARC:" as the detail gives whats compressed and whats not?

Edit: Or not as I just spotted the line above is already just ARC :(

I didn't notice it was that wide, yes, let me fix that.

[jhb]

I agree with shortening the line a bit so it fits in 80 cols. If you are worried about duplicating "ARC:" you could perhaps just use a whitespace prefix so you end up with something like:

Mem: 754M Active, 836M Inact, 75M Laundry, 3761M Wired, 10G Free
ARC: 2476M Total, 914M MFU, 1302M MRU, 1696K Anon, 140M Header, 118M Other
     1899M Compressed, 6065M Uncompressed, 2.45:1 Ratio, 318M Overhead
Swap: 3072M Total, 3072M Free

Also, "Sponsored by:" usually implies funding, but "Suggested by:" might work.

[smh]

In D9829#203014, @jhb wrote:

I agree with shortening the line a bit so it fits in 80 cols. If you are worried about duplicating "ARC:" you could perhaps just use a whitespace prefix so you end up with something like:

Mem: 754M Active, 836M Inact, 75M Laundry, 3761M Wired, 10G Free
ARC: 2476M Total, 914M MFU, 1302M MRU, 1696K Anon, 140M Header, 118M Other
     1899M Compressed, 6065M Uncompressed, 2.45:1 Ratio, 318M Overhead
Swap: 3072M Total, 3072M Free

I like this idea, looks nice

[allanjude]

Update the output to fit within 80 columns

Use jhb@'s suggestion and don't bother with a header

CPU: 0.1% user, 0.0% nice, 0.0% system, 0.0% interrupt, 99.9% idle
Mem: 72M Active, 13G Inact, 30G Wired, 81G Free
ARC: 20G Total, 12G MFU, 6304M MRU, 1853K Anon, 369M Header, 1685M Other

17G Compressed, 36G Uncompressed, 1.81:1 Ratio, 1238M Overhead

Swap: 4096M Total, 4096M Free