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36 Chapter 2. The /proc File System

2.2.26. /proc/slabinfo

This ﬁle gives information about memory usage on the slab level. Linux kernels greater than 2.2 use

slab pools to manage memory above the page level. Commonly used objects have their own slab

pools.

The values in this ﬁle occur in the following order: cache name, number of active objects, number of

total objects, size of the object, number of active slabs (blocks) of the objects, total number of slabs

of the objects, and the number of pages per slab.

It should be noted that active in this case means in use. An active object is one that is in use, and an

active slab is one that contains any used objects.

2.2.27. /proc/stat

This ﬁle keeps track of a variety of different statistics about the system since it was last restarted. The

contents of /proc/stat, which can be quite long, begins something like this:

cpu 1139111 3689 234449 84378914

cpu0 1139111 3689 234449 84378914

page 2675248 8567956

swap 10022 19226

intr 93326523 85756163 174412 0 3 3 0 6 0 1 0 428620 0 60330 0 1368304 5538681

disk_io: (3,0):(1408049,445601,5349480,962448,17135856)

ctxt 27269477

btime 886490134

processes 206458

Some of the more popular statistics include:

• cpu — Measures the number of jifﬁes (1/100 of a second) that the system has been in user mode,

user mode with low priority (nice), system mode, and the idle task, respectively. The total for all

CPUs is given at the top, and each individual CPU is listed below with its own statistics.

• page — The number of memory pages the system has written in and out from the disk.

• swap — The number of swap pages the system has brought in and out.

• intr — The number of interrupts the system has experienced.

• btime — The boot time, measured in the number of seconds since January 1, 1970, otherwise

known as the epoch.

2.2.28. /proc/swaps

This ﬁle measures swap space and its utilization. For a system with only one swap partition, the output

of /proc/swap may look similar to this:

Filename Type Size Used Priority

/dev/hda6 partition 136512 20024 -1

While some of this information can be found in other /proc ﬁles, swap provides for a very quick

snapshot of every swap ﬁlename, type of swap space, and total and used sizes (in kilobytes). The

priority column is useful when multiple swap ﬁles are in use, and some of them are preferred over

others, such as if they are on faster hard disks. The lower the priority, the more likely the swap ﬁle

will be used.

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Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Guida di Installazione Pagina 36