Squid_ The Definitive Guide - Duane Wessels [134]
diskd: DISKD Stats
This page is available only with the ./configure —enable-storeio=diskd option. It provides various statistics relating to the diskd storage scheme.
The sent_count and recv_count lines are counters for the number of I/O requests sent between Squid and the group of diskd processes. The two numbers should be very close to each other and could possibly be equal. The difference indicates how many requests are currently outstanding.
The max_away value indicates the largest number of outstanding requests. Similarly, the max_shmuse counter indicates the maximum number of shared memory blocks in use at once. These two values are reset (to zero) each time you request this page. Thus, if you wait longer between requests for this page, these maximum counters are likely to be larger.
The open_fail_queue_len counter indicates the number of times that the diskd code decided to return failure in response to a request to open a file because the message queue exceeded its configured limit. In other words, this is the number of times a diskd queue reached the Q1 limit. Similarly, block_queue_len shows how many times the Q2 limit has been reached. See the descriptions of Q1 and Q2 in Section 8.5.1.
The diskd page also shows how many requests Squid sent to the diskd processes for each of the six I/O operations: open, create, close, unlink, read, and write. It also shows how many times each operation succeeded or failed. Note, these counters are incremented only for requests sent. The open_fail_queue_len check occurs earlier, and in that case, Squid doesn't send a request to a diskd process.
config: Current Squid Configuration*
This option dumps Squid's current configuration in the squid.conf format. Thus, if you ever accidentally remove the configuration file, you can recover it from the running Squid process. By saving the output to a file, you can also compare (e.g., with the diff command) the running configuration to the saved configuration. Note, however, that comments and blank lines aren't preserved.
This option reveals potentially sensitive information, so it's available only with a password. You must add a cache manager password for the config option with the cachemgr_passwd directive. See Section 14.2.2 for specifics. Additionally, these cache manager passwords aren't displayed in this output.
comm_incoming: comm_incoming( ) Stats
This page provides low-level network I/O information to developers and Squid wizards. The loop that checks for activity on file descriptors is called comm_poll( ). Over the years, this function has become increasingly complicated in order to improve Squid's performance. One of those performance improvements relates to how often Squid checks certain network sockets relative to the others.
For example, the incoming HTTP socket is where Squid accepts new client connections. This socket tends to be busier than a normal data socket because each new connection comes through the incoming socket. To provide good performance, Squid makes an extra effort to check the incoming socket more frequently than the others.
At the top of the comm_incoming page, you'll see three incoming interval numbers: one each for ICP, DNS, and HTTP. The interval is the number of normal I/O events that Squid handles before checking the incoming socket again. For example, if incoming_dns_interval is set to 140, Squid checks the incoming DNS socket after 140 I/Os on normal connections. Unless your Squid is very busy, you'll probably see 256 for all incoming intervals.
The page also contains three histograms that show how many events occur for each incoming function call. Normally, the majority of the histogram counts occur in the low values. In other words, functions such as comm_select_http_incoming( ) usually handle between one and four events.
ipcache: IP Cache Stats and Contents
The IP cache contains cached results of hostname-to-address lookups. This cache manager page displays quite a lot of information. At the top of this page you'll