Re: [Xen-devel] how to trace scheduling overheads using xentrace/xenalyze

[Dario Faggioli <raistlin@xxxxxxxx>]

On Tue, 2015-10-06 at 20:46 -0700, Yu-An(Victor) Chen wrote:
> Hi,
> 
Hi,

> I am new to xen environment 
>
Welcome :-)

> and I am wondering how to trace scheduling overhead of guest vm using
> xentrace/xenalyze ?
> 
Have you had a look at this blog entry? It's from some time ago, but
the basic concepts should still hold.

 https://blog.xenproject.org/2012/09/27/tracing-with-xentrace-and-xenal
yze/

Of course, that tells how to use the tools (xentrace and xenalyze), not
how to "trace scheduling overhead". For doing so, I think you should
first define what it is really that you want to measure (many
definitions of scheduling overhead are possible) and, only after that,
check whether it is possible to do that with existing tools.

> I have tried using $xentrace -D -e all -S 256 {filename}
> 
> and then use various xenalyze options but most of them gave me empty
> result, and I dont really see where I can get scheduling overhead so

>
Mmm... The command above works for me (just tried). However, '-e all'
is a lot of data, and it may actually take a bit to xenalyze to parse
it.

Maybe, if you are interested in tracing scheduling related events, use
the appropriate event mask?

> I can see how are the jobs are scheduled and its execution time and
> stuff. Please point me to a direction. Thank you!
> 
Again, you should detail more what you think 'scheduling overhead' is.
If you are interested in seeing how and where the vcpus are scheduled,
you want a dump.

With this:

 xentrace -D -e 0x0002f000 trace.bin

and then this:

 xenalyze --dump-all trace.bin

Here's an excerpt of what I get:

]  0.000019647 x----------  -- d32767v0   22802(2:2:802) 0 [ ]
]  0.000019969 x----------  -- d32767v0   22805(2:2:805) 5 [ 7fff 0 0 0 0 ]
   0.000020474 x----------  -- d32767v0 runstate_continue d32767v0 
running->running
]  0.000021170 ----x------  -- d32767v4   22802(2:2:802) 0 [ ]
]  0.000021370 ----x------  -- d32767v4   22805(2:2:805) 5 [ 47fff 0 0 0 0 ]
   0.000021817 ----x------  -- d32767v4 runstate_continue d32767v4 
running->running
]  0.000022235 ---------x-  -- d32767v9   22802(2:2:802) 0 [ ]
]  0.000022467 ---------x-  -- d32767v9   22805(2:2:805) 5 [ 97fff 0 0 0 0 ]
   0.000022983 ---------x-  -- d32767v9 runstate_continue d32767v9 
running->running
]  0.000023438 --------x--  -- d32767v8   22802(2:2:802) 0 [ ]
]  0.000023638 --------x--  -- d32767v8   22805(2:2:805) 5 [ 87fff 0 0 0 0 ]

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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