[ofa-general] IB performance stats (revisited)

[Hal Rosenstock]

On Wed, 2007-06-27 at 13:24, Mark Seger wrote:
> Hal Rosenstock wrote:
> 
> >On Wed, 2007-06-27 at 13:07, Mark Seger wrote:
> >  
> >
> >>>The performance managers deal with the counter stickiness (by resetting
> >>>them when they think they need to). They typically export their data
> >>>although this is not specified by IBA so it is in a vendor proprietary
> >>>manner.
> >>> 
> >>>
> >>>      
> >>>
> >>so I guess these guys are poor citizens as well...
> >>    
> >>
> >
> >Not sure what you mean.
> >  
> >
> I consider it poor form to zero counters out from someone else who might 
> be in the middle of trying to read them and though that's what you mean 
> when you said why I was doing was "Yes, it is _bad_ if there are 
> essentially multiple performance managers resetting the counters."  I am 
> most definately guilty as charged and trying real hard to get out from 
> under which is why I suggested a module that exports wrapping counters 
> to /proc.  Then, as long as ALL utilities rely on those numbers, the 
> module can reset them all likes and nobody interfers with each other 
> since there is only one program doing that.

Another approach would be to have the PMA inform the kernel that the
counters were reset (perhaps including the values prior to the reset) so
that these could be factored into the local set of counters. There is
nothing in the spec that precludes this although it has not been
implemented this way. Then there would't be a reason for a local manager
to have to play these games. It would mean that there would need to be a
performance manager running in the subnet which may not be acceptable
for some installations; not sure.

> >>the real issue as I see it then means nobody can trust the data if 
> >>randon tools randomly reset the counters.  a real shame...
> >>    
> >>
> >
> >I consider this to be a real rather than random app for this. Guess it
> >depends on what one considers random.
> >  
> >
> I used the term 'random' loosely, but my point is as long as anyone can 
> reset the counters and you never know if it's happening or not, you'll 
> get bogus data 

Agreed.

> and I'm trying to find a way to get around it.

Understood.

-- Hal

> -mark
> 
> >-- Hal
> >
> >  
> >
> >>-mark
> >>
> >>
> >>    
> >>
>