Date: Sun, 1 Feb 2009 23:40:42 +0100 From: Borja Marcos <borjamar@sarenet.es> To: Robert Watson <rwatson@FreeBSD.org> Cc: freebsd-stable@freebsd.org Subject: Re: Puzzling change in performance Message-ID: <2C4CD129-43B3-49FA-8208-FAC25191D2F2@sarenet.es> In-Reply-To: <alpine.BSF.2.00.0901311823490.46645@fledge.watson.org> References: <C99CD0EF-F42D-43BC-9FFC-0A37FE0251E4@sarenet.es> <alpine.BSF.2.00.0901311823490.46645@fledge.watson.org>
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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.
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