Processes widget fails with ps from BusyBox about gotop

[xxxserxxx]

On a suggestion over in shirou/gopsutil#842 by @AtakanColak, I tried go-sysinfo. Despite eliminating the forking & parsing of output, and string manipulation and parsing to produce numbers, it's still twice as slow as forking ps. It's significantly faster than gopsutil, but still more CPU intensive than forking. I feel like I have to keep saying that, because it's so difficult to believe. In any case, it stays how it is on Linux, and I think the way forward is one of the suggestions above: detect when gotop is running in busybox and use go-sysinfo there.

[xxxserxxx]

Gory details are in shirou/gopsutil#842, but the summary is: a benchmark shows that elastic/go-sysinfo is marginally faster than the current forking/parsing code. It doesn't explain why top showed that version as having higher CPU use, but I'm willing to give it a shot if it means supporting more environments.

[xxxserxxx]

Another hiccup: go-sysinfo fails to get information about many processes when run as a user because it doesn't have access to all processes in /proc. This may be insurmountable.

[xxxserxxx]

Busbox support sounds good to me. It would probably require us to do some check on the environment on start and adjust the ps flags. I'm curious what the adjustments would be. Is that actually the entirety of the man page? 😂 If not, could you copy the contents into a gist or link it?

So can you test this command: ps -o pid,comm,pcpu,pmem,args? Also, there's been some issues with the ps columns being cropped, so if that happens when running that, then you can try doing ps -o pid,comm=superlongheaderasdfasdfasdfsdaf etc.

[xxxserxxx]

Unfortunately it is the complete manpage :(

[~] # ps -h
ps: invalid option -- 'h'
BusyBox v1.24.1 (2018-12-28 02:26:16 CST) multi-call binary.

Usage: ps [-o COL1,COL2=HEADER] [-T]

Show list of processes

        -o COL1,COL2=HEADER     Select columns for display
        -T                      Show threads

QNAP Options:
        --columns N
[~] #

With yours commands i get :

ps -o pid,comm,pcpu,pmem,args 
ps: bad -o argument 'pcpu', supported arguments: user,group,comm,args,pid,ppid,pgid,etime,nice,rgroup,ruser,time,tty,vsz,stat,rss

I removed pcpu and pmem (because it's not recognized) and i get things like this :

[~] # ps -o pid,comm,args
  PID  COMMAND          Command
    1 init             init
    2 kthreadd         [kthreadd]
    3 ksoftirqd/0      [ksoftirqd/0]
    5 kworker/0:0H     [kworker/0:0H]
    7 rcu_sched        [rcu_sched]
...

I don't see any problems with cropping (i have some very long "Command" entries).

[xxxserxxx]

So it looks like ps on busybox doesn't support per process cpu usage or memory reporting. So we should check if we're on busybox and then our only option is to remove the unsupported flags and only show PID and command.

[xxxserxxx]

The only way i find to get cpu or memory reporting is to use top.
If you need other tests, i'm available ;)

[xxxserxxx]

Some new ideas about different ways to fix this:

1. detect when a system uses busybox, then use cli args appropriate for ps on a busybox system, but we won't be able to get per-process cpu or memory usage
2. require users to download and install procps on their system as a workaround
3. directly gather process information ourselves by traversing /proc, or use the implementation provided by gopsutil

3 sounds best to me. We were originally using gopsutil to gather process information but I forget why we switched of it. And it should be easy to test gopsutil's implementation (I've just been busy).

[xxxserxxx]

Note to self:

docker run -it --name gotopbb --rm busybox
CGO_ENABLED=0 go build -a -v -o gotop ./cmd/gotop
docker cp ./gotop gotopbb:/bin/

[xxxserxxx]

• directly gather process information ourselves by traversing /proc, or use the implementation provided by gopsutil

3 sounds best to me. We were originally using gopsutil to gather process information but I forget why we switched of it. And it should be easy to test gopsutil's implementation (I've just been busy).

(Emphasis mine). Well, I found out why. CPU use quadruples under the gopsutil library vs repeatedly forking ps. Frankly, this surprises the heck out of me. However, changing to gopsutil does (a) remove the need for all of the OS-specific procs sources, and (b) enable procs to work properly on BusyBox.

I've filed shirou/gopsutil#842, and will leave this ticket open until a clear path forward is defined.

@Mikiya83 FYI