Re: [squid-users] object cached with certainty

On 2014-02-14 10:53, Carlos Defoe wrote:
> It's squid 3.3.8.
>
> Yeah, I had forgotten about the replacement policies... in fact, I
> read the "definitive guide", but it was almost 10 years ago.
>
> I tried with an empty disk cache, default replacement policies, clean
> start, and now it gets cached, but in memory. I'll wait till both
> cache_mem and cache_dir get full, to test again.
>
> Another possiblity that comes in mind is that the aufs threads could
> have been very busy, thus discarding the objects instead of writing it
> to disk.
>
> One more question: how squid decides that an object should be stored
> on disk instead of RAM?

When they first arrive this is the sole consideration is whether it is
bigger or smaller than this limit:
   http://www.squid-cache.org/Doc/config/maximum_object_size_in_memory/

Objects with undefined length are assumed to be infinitely big and thus
require disk backing until further information is known about it (ie
delivered info causes it to exceed the memory limit, or the
end-of-object proves its best place).

> Those jpeg images that are now cached on RAM,
> will they ever be stored on disk?

Maybe, if the RAM is full and a new object needs space the least-popular
objects will be either dropped (if expired already) or pushed out to
disk cache.

Where "least-popular" is defined by the
http://www.squid-cache.org/Doc/config/memory_replacement_policy/
algorithm.

Amos
Received on Thu Feb 13 2014 - 23:51:53 MST