Re: LRU expiration age

Neale Banks wrote:

> Just to make sure I have this right:
>
> This would mean that we are expiring from the disk cache objects which
> have been "Least Recently Used" and that these have been sitting in the
> cache unrequested for "about one week", to make room for new objects
> (which have just been requested)?

Yes.

> And the stastical game we are playing here in the optimisation is
> something like how long we need to keep unreferenced objects before the
> probability that they will be referenced in the "near future" and still
> "current" diminishes to a level "suitably" close to zero.

Yes.

> Lastly, the LRU age is not something we configure, but is the measure of
> the age of objects dropped from the cache as above? The obvious
> changeable inputs that influence the LRU age are the size of the disk
> cache and the volume of (cacheable traffic) through the squid?

Correct.

All you can possibly configure is an upper bound. The lower bound is the
maximum capacity to store objects.

If you'd like to read up a bit on the subject of cache object
replacement, then see many of the papers presented at the yearly Web
Cache Workshops and the references therein (4 workshops held so far).

--
Henrik Nordstrom
Squid hacker