Re: Squid slow during cleanup

> > The performance degradation is a major issue, with over 5,000 local
users
> > generating almost 2 million requests a week, as well as 6 squid
neighbours
> > generating another 4+ million ICP and TCP requests. Users report that
the
> > proxy performance is almost unbearable when it is in this state.
> >
> > Has anyone else encountered such a problem and have any suggestions?

The best idea is probably the one others on this list have suggested: to
use ttl's to keep the cache naturally to size. But that's a black art!
 And I've just started experimenting in this direction.

Since the problem was pressing, though, and since I knew that the total
amount of virtual memory used by Squid far exceeded the main memory of our
machine, I succeeded in getting our management to buy more memory.

Adding enough main memory to keep the complete set of Squid processes
(including perhaps system processes that are involved in, say, DNS
lookups) has helped reduce the impact of a garbage collection somewhat
(from a factor of 10 in average transmission rate degradation to a factor
of 3 or so, which slows it down to roughly what you'd get without the
cache). For our now 300000 TCP + 250000 UDP requests handled per day (user
base is 20000 potentially; no idea how many for real), and a cache size of
7GB, the minimum amount of memory turned out to be 256MB, and even that is
on the low side. To figure out how much you'd need, just add up the sizes
of the squid, dnsserver and ftpget processes (on SUN: add nscd size) that
you get during the garbage collection, add a couple percent, and make sure
all of it fits in your hardware main memory. If you can afford it, that
is.

(I wish the slow scan were smart enough to know how many files it has to
delete each time it's called in order to keep up with the current growth
rate of the swap space).

Hope this helps.

Andreas

-- 
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