Squid_ The Definitive Guide - Duane Wessels [133]
store_io
Store IO Interface Stats
pconn
Persistent Connection Utilization Histograms
refresh
Refresh Algorithm Statistics
delay
Delay Pool Levels
forward
Request Forwarding Statistics
client_list
Cache Client List
netdb
Network Measurement Database
asndb
AS Number Database
carp
CARP Information
server_list
Peer Cache Statistics
non_peers
List of Unknown Sites Sending ICP Messages
leaks: Memory Leak Tracking
This page is available only with the ./configure —enable-leakfinder option and is intended for developers trying to track down memory leaks. The page shows each memory pointer being tracked and where and when it was most recently referenced. See the Squid Programmer's Guide (http://www.squid-cache.org/Doc/Prog-Guide/) for more information about Squid's leak-finder feature.
mem: Memory Utilization
The memory utilization page shows a large table of numbers. Each row corresponds to a different pool of memory. The pools have names like acl_list and MemObject. Much of this information is of interest to developers only. However, a few columns are worth mentioning here.
* * *
Tip
It is important to keep in mind that this table doesn't represent all the memory allocated by Squid. Some memory allocations aren't tracked and don't appear in the table. Thus, the Total row may be much less than Squid's actual memory usage.
* * *
The impact column shows each pool's contribution to the total amount of memory allocated. Usually, the StoreEntry, MD5 digest, and LRU policy node pools take up most of the memory.
If you are a developer, you can use this page to look for memory leaks. The column labeled high (hrs) shows the amount of time elapsed since the pool reached its maximum size. A small value in this column may indicate that memory for that pool isn't being freed correctly.
You can also use this page to find out if certain features, such as netdb, the ipcache, and client_db consume too much memory. For example, the ClientInfo pool is associated with the client_db feature. The memory utilization page shows you how much memory you can save if you disable client_db in squid.conf.
cbdata: Callback Data Registry Contents
The Callback Data Registry is an internal Squid programming feature for managing memory pointers. Currently, this cache manager page doesn't provide much useful information, apart from the number of active cbdata pointers being tracked. In earlier Squid versions, the cbdata feature was implemented differently and this page provided some information to developers debugging their code.
events: Event Queue
Squid maintains an event queue for a number of tasks that must occur separately from user requests. Perhaps the most important of these is the periodic task that maintains the disk cache size. Every second or so, this task runs and looks for cache files to remove. On this page, you can see all tasks currently scheduled for execution. Most likely, you'll not find this very interesting unless you are hacking the source code.
squidaio_counts: Async IO Function Counters
This page is available only with the ./configure —enable-storeio=aufs option. It shows counters for the number of open, close, read, write, stat, and unlink requests received. For example:
ASYNC IO Counters:
Operation # Requests
open 15318822
close 15318813
cancel 15318813
write 0
read 19237139
stat 0
unlink 2484325
check_callback 311678364
queue 0
The cancel counter is normally equal to the close counter. This is because the close function always calls the cancel function to ensure that any pending I/O operations are ignored.
The write counter is zero because this version of Squid performs writes synchronously, even for aufs.
The check_callback counter shows how many times the main Squid process has checked the done queue for completed operations.
The queue value indicates the current length of the request queue. Normally, the queue length should be less than the number of threads × 5. If you repeatedly observe a queue length larger than this, you may be pushing Squid