Re: meanings of variables in MIB?

From: Scott Prater <>
Date: Tue, 04 Apr 2000 14:12:00 +0200

Okay, here´s a list of some of the basic variables I think a cache
manager would want to track, with their definitions, as far as I
understand them. Many questions have I.

Basically, I want to start by tracking the following:

  * amount of memory squid has allocated (obtainable by "ps"?)
  * amount of memory squid is actually using (to contrast with the
above, and identify possible memory leaks)

  * amount of disk space squid is actually using (as opposed to simply
marking as its own -- obtainable by "du"?)

  * number of objects in cache

  * number of requests (HTTP and all) that have come into squid
  * number of requests (HTTP and all) that have been served from cache

  * number of requests (HTTP and all) that have been retrieved from

  (ideally, number of requests served from cache + number of requests
served from internet + number of unrealizable requests = number of
requests from clients)

  * byte hit ratio (percentage of requests, in bytes, served from cache)

  * object hit ratio (percentage of requests, in number, served from

As I understand the MIB, I can obtain all the above with the variables
described below. Please correct me if I'm wrong. Also, If I've made
any mistakes in the descriptions below, I'd appreciate corrections.

cacheSysVMsize: size of Virtual Memory in KB. Is this the amount of
disk space squid is currently using for as a form of virtual memory?
Does this include swap? I'm unclear on what exactly this variable
means, and how it relates to operating system virtual memory. I've read
the squid FAQ on this topic, but I need a little bit more of the
in-a-nutshell introduction.

cacheSysStorage: size of cache stored on disk in KB (should be roughly
the same as du output for cache directory tree?)

cacheMemUsage: amount of system memory allocated by the cache (subset
of total memory squid occupies, as seen by "ps"?)

cacheNumObjectCount: number of objects in cache (total of objects in
disk storage, in memory (current objects), and in Virtual Memory?)

cacheServerRequests: total number of requests (of all kinds) to server
from clients (value that only grows)

(Is there an equivalent to the non-existent cacheServerHits value that I
can use to determine the object hit ratio?)

cacheServerInKb: total number of kilobytes read from internet into
server (value that only grows)

cacheServerOutKb: total number of kilobytes sent from server to clients
(value that only grows)

If I understand the above cacheServerInKb and cacheServerOutKb variables
correctly, I can obtain the byte hit ratio (as opposed to the object hit
ratio) this way:

        byte hit ratio =
                (cacheServerOutKb - cacheServerInKb)/cacheServerOutKb
        the closer this number is to 1 (100%), the better my

cacheRequestHitRatio: object hit ratio (see above)

cacheRequestByteRatio: byte hit ratio (see above)

cacheClientHttpRequests: number of HTTP requests from client (value
that only grows)

cacheHttpHits: number of HTTP requests satisfied from within cache
(value that only grows)

cacheHttpInKb: number of KB of HTTP requests squid had to retrieve from
outside (value that only grows)

cacheHttpOutKb: number of KB of HTTP requests squid served to clients
(value that only grows)


Scott Prater

Duane Wessels escribió:
> On Wed, 29 Mar 2000, Scott Prater wrote:
> > lists, and using logic and intuition. Is there one place where all the
> > different statistics are explained, for the benefit of new cache
> > managers like myself?
> There probably is not such a document/place. If you have specifc
> questions that I can answer, I will be happy to put them in the
> FAQ.
> Duane W.

Scott Prater			
Analista de Sistemas
Ramón Gordillo 1-entlo
46010 Valencia
+34-96-361-8776 (tel)
+34-96-360-5508 (fax)
Received on Tue Apr 04 2000 - 06:17:32 MDT

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