ban_lurker_age, ban_lurker_sleep

[Poul-Henning Kamp]

--------
In message <571112C2.5070607 at schokola.de>, Nils Goroll writes:

>I've just pushed two minor improvements on the documentation, but I'd suggest
>two changes
>
>* ban_lurker_age:

>but we also increase the likelihood of bans requiring request-time evaluation,
>which is bad for latency.

The important thing is for the lurker to not get in the way of
request-time evaluation, because it will be definition waste a lot
of time on objects clients don't care for, thus needlessly delaying
the ones the clients ask for.

The right thing to do with respect to both ban_lurker_{age|sleep}
is probably to look at the rate of req-time evaluations and modulate
the lurker activity to minimize interference.

Likewise the mutex contest delay should increase in response to
rate of req-time evaluations.

For instance we could make a param which says how many ban-checks
per second we allow.  If the req-time processing leaves any
unused, the lurker is free to "fill up the quota".  Unfortunately
such "quota" parameters need to scale and I have no idea on what (ncpu ?)

But again, data-driven analysis is most welcome.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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