Re: use of -z io,stat

[ronnie sahlberg <ronniesahlberg () gmail com>]

Hi,

"I want to calculate how much time the Client spent thinking:"

This is actually a very difficult question to answer. Especially since
with most clients/most protocols doing multithreaded concurrent i/o
"client-slowness" is usually never as simple as delta between a reply
and to the next request goes out but
much more complex things to model like "slow client does slightly less
concurrent i/o"

While measuring server performance is pretty straightforward,
measuring client performance is often surprisingly hard problem.



One method I have found that works surprisingly well (for me) is the
LOAD calculation in wireshark.
This is a measure of the average queue depth between a client and a
server. As the client issues new I/O, the queue grows, as the server
completes a request the queue shrinks.
This provides a metric to compare the relative speeds between a client
and a server and how they are matched/where the bottleneck is.


See this for a presentation I did a long time ago that contains a
description of LOAD :

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CC0QFjAA&url=http%3A%2F%2Fwww.snia.org%2Fsites%2Fdefault%2Ffiles2%2Fsdc_archives%2F2008_presentations%2Fmonday%2FRonnieSahlberg_UsingWireshark.pdf&ei=4XWmUc-gAqmqiQKM9oHQCQ&usg=AFQjCNFdiD93MJaGOBkol17t2KcncXEHvw&sig2=xIyIYZTOFoQs2gxKV8p0pA


regards
ronnie sahlberg


On Sun, May 26, 2013 at 8:42 AM, Stuart Kendrick <skendric () fhcrc org> wrote:
> I'm trying to teach myself how to use the '-z io,stat' options in tshark
>
> I was imagining that the following would tell me how many seconds the trace covers
>
> tshark -r sample-http.pcapng -o tcp.calculate_timestamps:TRUE -qz "io,stat,0,SUM(tcp.time_delta)tcp.time_delta"
>
> =============================================
> | IO Statistics                             |
> |                                           |
> | Interval size: 11.1 secs (dur)            |
> | Col 1: Frames and bytes                   |
> |     2: SUM(tcp.time_delta)tcp.time_delta  |
> |-------------------------------------------|
> |              |1               |2          |
> | Interval     | Frames | Bytes |    SUM    |
> |-------------------------------------------|
> |  0.0 <> 11.1 |    216 | 45453 | 23.817352 |
> =============================================
>
> capinfos sample-http.pcapng
> File name:           sample-http.pcapng
> [...]
> File size:           53 kB
> Data size:           45 kB
> Capture duration:    11 seconds
> [...]
>
> But apparently not:  '23.817352' does not equal '11 seconds'
>
> https://vishnu.fhcrc.org/wireshark/sample-http.pcapng
> I'm using wireshark 1.10.0rc2
>
> What am I not understanding about this '-z io,stat' feature?
>
> --sk
>
> Stuart Kendrick
> FHCRC
>
> P.S.
>
> My actual use case will be more complex than this.  This trace was taken next to the Client.
> I want to calculate how much time the Client spent thinking:
> tshark -r sample-http.pcapng -o tcp.calculate_timestamps:TRUE -qz "io,stat,0,SUM(tcp.time_delta)tcp.time_delta and 
> tcp.dstport==80"
>
> and how much time the Network + Server spent thinking:
> tshark -r sample-http.pcapng -o tcp.calculate_timestamps:TRUE -qz "io,stat,0,SUM(tcp.time_delta)tcp.time_delta and 
> tcp.srcport==80"
>
> To give myself insights into how much of the total transaction time the Client is contributing versus that of the 
> Network + Server.
>
> But I figure that if I cannot even persuade tshark to sum every value in the DeltaT column, then I'm not ready to 
> progress to the real-world use case.
>
>
> P.P.S.
> The Average function gives me a plausible answer:
>
> tshark -r sample-http.pcapng -o tcp.calculate_timestamps:TRUE -qz "io,stat,0,AVG(tcp.time_delta)tcp.time_delta"
>
> =============================================
> | IO Statistics                             |
> |                                           |
> | Interval size: 11.1 secs (dur)            |
> | Col 1: Frames and bytes                   |
> |     2: AVG(tcp.time_delta)tcp.time_delta  |
> |-------------------------------------------|
> |              |1                |2         |
> | Interval     | Frames |  Bytes |    AVG   |
> |-------------------------------------------|
> |  0.0 <> 11.1 |    473 | 349155 | 0.050354 |
> =============================================
>
>
> But when I sanity-check this calculation using Excel, I see a different result:
> 0.023518s
>
> ___________________________________________________________________________
> Sent via:    Wireshark-users mailing list <wireshark-users () wireshark org>
> Archives:    http://www.wireshark.org/lists/wireshark-users
> Unsubscribe: https://wireshark.org/mailman/options/wireshark-users
>              mailto:wireshark-users-request () wireshark org?subject=unsubscribe
___________________________________________________________________________
Sent via:    Wireshark-users mailing list <wireshark-users () wireshark org>
Archives:    http://www.wireshark.org/lists/wireshark-users
Unsubscribe: https://wireshark.org/mailman/options/wireshark-users
             mailto:wireshark-users-request () wireshark org?subject=unsubscribe