[bind10-dev] Enabling/disabling logging on per-message basis

[JINMEI Tatuya / 神明達哉]

At Tue, 27 Mar 2012 12:36:44 +0200,
Michal 'vorner' Vaner <michal.vaner at nic.cz> wrote:

> > To me, it's not so obvious.  We have quite a lot of debug level log
> > messages in performance sensitive path, so a downgrade of 27% looks
> > still alarming, even if I understand other stuff should dominate the
> > overall process.
> > 
> > Personally, I'd still keep this overhead minimum (e.g. within 5%
> > range) unless the optimization requires hundreds of additional code.
> 
> OK, I made another small experiment. I configured bind10 here with
> full debug output and counted 7 messages per successful query, 7 per
> NXDOMAIN and 3 when no such zone (for in-memory). This can differ by
> amount of additional data and like that, so lets count 10 per query
> to be safe and have easier mathematics.
> 
> Looking at the emails Jeremy sent, we have something 40k QPS per
> core. OK, count 50k, again to be on the safe side.
> 
> As measured by me, the orders of logging messages is above 50M MPS
> (again error to the safe side). That means our .5M messages output
> for that form 1% of the time of the answering process. Even by
> making the process of determining the message should not be logged
> twice as slow would be 1% difference in the total performance.

I'm afraid I don't understand the measurement description.  But if you
mean you compared the two versions of BIND 10:
A: the current (= something like the latest release) version
B: the current version with the proposed change in this thread,
and B is only 1% slower than A in terms of max qps it can handle
(measured by queryperf or something), then I agree the performance
wouldn't be an issue.

> So I'm stating it again: we don't have to worry about it making the
> server too slow. Now we need to worry if the feature provides enough
> benefits (both in usability and „marketing“) to be worth the work we
> would put into implementing it and the one more item in the Logging
> configuration module. I think the feature is worth it.

I see it could be useful.  On the other hand, as an armature operator
I've never needed to suppress particular log message, so I'm not sure
(just because of the lack of experience) if the benefit is imaginary
or is widely desired.  Ideally we could get more input about serious
operators rather than developers.  But if we cannot get that
information easily, I don't oppose to trying to implement it.

---
JINMEI, Tatuya
Internet Systems Consortium, Inc.