systemtap/pcp integration pmda 0.1

[David Smith <dsmith at redhat dot com>]

Here's version 0.1 (up from 0.01!) of my systemtap/pcp integration work
that uses systemtap (https://sourceware.org/systemtap/) to export JSON
data and a pcp (http://www.performancecopilot.org/) python pmda that
reads and processes the JSON data.

At this point things work reasonably well (at least with the test
systemtap script I've attached). There are still lots of "FIXME"
comments spread throughout the code. This time the systemtap side of
things has come along and you no longer have to hand-write JSON to
output data. The script itself is based on some work that Will
Cohen has been doing to measure network latency. Note that the script
does output live data.

The biggest addition this time is array handling, which was a bit
tricky. I'm still not sure the indom handling on the pcp side is correct
(but it seems to follow the other python pmdas).

Here's what live data looks like from pcp:

====
# pminfo -df stap_json

stap_json.json.dummy2
    Data Type: string  InDom: PM_INDOM_NULL 0xffffffff
    Semantics: instant  Units: none
    value "dummy2"

stap_json.json.dummy_array.dummy2
    Data Type: string  InDom: 130.1 0x20800001
    Semantics: instant  Units: none
    inst [0 or "1"] value "def"
    inst [1 or "0"] value "abc"
    inst [2 or "2"] value "ghi"

stap_json.json.dummy_array.dummy1
    Data Type: 64-bit int  InDom: 130.1 0x20800001
    Semantics: counter  Units: none
    inst [0 or "1"] value 2
    inst [1 or "0"] value 1
    inst [2 or "2"] value 3

stap_json.json.net_xmit_data.xmit_latency
    Data Type: 64-bit int  InDom: 130.0 0x20800000
    Semantics: counter  Units: none
    inst [0 or "fake1"] value 0
    inst [1 or "fake2"] value 0
    inst [2 or "eth0"] value 319

stap_json.json.net_xmit_data.xmit_count
    Data Type: 64-bit int  InDom: 130.0 0x20800000
    Semantics: counter  Units: none
    inst [0 or "fake1"] value 0
    inst [1 or "fake2"] value 0
    inst [2 or "eth0"] value 2304551

stap_json.json.read_count
    Data Type: 64-bit int  InDom: PM_INDOM_NULL 0xffffffff
    Semantics: counter  Units: none
    value 8

stap_json.json.xstring
    Data Type: string  InDom: PM_INDOM_NULL 0xffffffff
    Semantics: instant  Units: none
    value "testing, 1, 2, 3"
====

The pcp pmda still only supports one systemtap script at this point. I
ran the attached systemtap script using the following command line to
produce the output above.

# stap -m json -v ./net_xmit_json5.stp eth0 fake1 fake2

Any comments/feedback would be appreciated.

-- 
David Smith
dsmith@redhat.com
Red Hat
http://www.redhat.com
256.217.0141 (direct)
256.837.0057 (fax)

Attachment: net_xmit_json5.stp
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