Re: Fwd: Any way to find the network usage by a process?

[Mike Mason <mmlnx@us.ibm.com>]

Frank Ch. Eigler wrote:
> Mike Mason <mmlnx@us.ibm.com> writes:
>
> > Here's a variation of Jose's script that uses the networking tapset
> > and prints top-like output for transmits and receives.  [...]
>
> Thanks for posting it to the systemtap wiki.
>
> Some minor style suggestions follow:
>
> > [...]
> >          ifxmit_p[pid(), dev_name] ++
> >          ifxmit_b[pid(), dev_name] += length
>
> These could be collapsed into a single statistics-aggregate array: 
> #          ifxmit[pid(), dev_name] <<< length
> Then the printing routine would use @count(ifxmit[...]) and @sum(ifxmit[...])
> to extract the two values.  Same of course for ifrecv.

I tried that and got the following output:

  PID   UID DEV     XMIT_PK RECV_PK XMIT_KB RECV_KB COMMAND
    0     0 eth0          9      10     486     672 swapper
ERROR: empty aggregate near identifier 'execname' at nettop.stp:35:4
WARNING: Number of errors: 1, skipped probes: 0

Apparently using @sum on empty aggregates isn't allowed. I expected 0's to 
be returned. The only way to avoid the error is use @sum only if @count > 
0, which makes the printf too complex in my opinion.

> >          execname[pid()] = execname()
> >          user[pid()] = uid()
> >          ifdevs[pid(), dev_name] = dev_name
>
> Calling pid() so many times is worse than calling it once and caching
> the result in a local variable ("p = pid()").  

Agreed.  I'll change that.

> The way that the script tracks pid-to-uid and pid-to-execname mappings
> is not bad, though if that part were moved to new probes on fork or
> exec, it would allow the network-related probes to run concurrently on
> an SMP without fighting over locks.

But that would only catch processes created after the script starts, correct?

- Mike

> - FChE

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