Puzzling change in performance

[Borja Marcos]

On Jan 31, 2009, at 7:27 PM, Robert Watson wrote:

> There are basically three ways to go about exploring this, none  
> particularly good:
>
> (1) Do a more formal before and after analysis of performance on the  
> box,
>   perhaps using tools like kernel profiling, hwpmc, dtrace, etc.

Machine in production, I cannot do it :(

> (2) Do a binary search to narrow down the date of the change that  
> improved
>   things until it becomes clear which mattered.


> (3) Hope someone annecdotally remembers something that might or  
> might not be
>   it and assume they're right.
>
> Of these, I'd guess (2) is actually the most effective way to go  
> about it, but is potentially time-consuming.  As you point out, the  
> most interesting question is whether, when you go back to 7.0,  
> things suddenly get slower again, or not.  Typically long uptimes  
> don't lead to performance problems on FreeBSD (in my experience) so  
> I think that's unlikely to be the source.  There are a lot of  
> improvements in 7.1 relating to performance, but none particularly  
> stands out for me as having the effect you describe.  If you're  
> really curious, I would try to pin it down with a binary search.

I will have to learn how to use dtrace, I think. This is quite weird.  
And in a lot of years I haven't seen a FreeBSD system degraded because  
of a long uptime. Something in userland must be the culprit...

As I see (I don't administer the machine but co-administer it) there's  
a Qmail system with some AV crap... and now I see that active memory  
had gone up, and is much lower after the update.

I'll keep investigating.. the kind of answer I was looking for was a  
"oh, yes, there was a problem that degraded, blah, blah, blah".

The graphs can be accessed here: http://194.30.110.21/orca/

It's behind an ADSL, so expect slow performance.






Borja.