[Pharo-project] Which are the limitations of MessageTally?? Re: new Cog VMs uploaded

Mariano Martinez Peck marianopeck at gmail.com
Mon May 16 22:01:17 CEST 2011


Thanks eliot for your explanations. I will give it a try to SystemProfiler

Thanks

On Tue, May 10, 2011 at 7:26 PM, Eliot Miranda <eliot.miranda at gmail.com>wrote:

>
>
> On Sun, May 8, 2011 at 5:07 AM, Mariano Martinez Peck <
> marianopeck at gmail.com> wrote:
>
>>
>>
>>  What approach do you suggest should I take?
>>>>
>>>
>>> I have no idea.  You could try and break down the various activities and
>>> benchmark them separately I suppose.  You could look at the profiles you're
>>> already generating in higher resolution to see where the time is going.  You
>>> could also try and extract the SystemProfiler from OpenQwaq, which will run
>>> on Cog, and is better than MessageTally.  Andreas wrote it to get around
>>> some of MessageTally's limitations.  It should hopefully show primitives
>>> quite accurately.
>>>
>>>
>> Hi. I have already read this several times. From you now, from Alexandre
>> Bergel, from Henrik Johansen, etc. But no one (or maybe I didn't see it)
>> give a list of the real existent MessageTally limitations or problems. So
>> far, the only thing I read is what Eliot says here: "show primitives quite
>> accurately"
>>
>> So...which are the rest and what is solved by the SystemProfiler from
>> OpenQwaq ??
>>
>
> MessageTally works by using delays to cause a high-priority process to
> interrupt the process being profiled.  So the sample is taken only at a
> suspension point.  The SystemProfiler support in the VM takes a sample
> either after a primitive has run or when the VM is checking for events, so
> it takes more accurate samples.  Further, the SystemProfiler's VM support
> also samples the active process when collecting the sampled method, so it
> more accurately ascribes profiles to processes.  MessageTally only profiles
> a single process.
>
>  Both suffer from a bug my colleague Yaron Kashai observed this week at
> Cadence, which is that if GC pauses are long then both profilers will
> under-measure the GC costs because they both take a single sample before
> measurement.  So e.g. if a GC pause lasts five times longer than the poll
> time only one sample will be takem.  Ideally the SystemProfiler would be
> extended to maintain a list of sampled methods and processes.
>
>
> best,
> Eliot
>
>
>> Thanks in advance,
>>
>>
>> Mariano
>>
>>
>>
>>
>>
>>> HTH
>>> Eliot
>>>
>>>
>>>>
>>>> Cheers
>>>> Philippe
>>>>
>>>>
>>>>
>>>
>>
>>
>> --
>> Mariano
>> http://marianopeck.wordpress.com
>>
>>
>


-- 
Mariano
http://marianopeck.wordpress.com
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