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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 following is a portion of a typical

/proc/slabinfo

virtual file:

slabinfo   version: 1.1

kmem_cache

64

68

112

2

2

1

nfs_write_data

0

0

384

0

0

1

nfs_read_data

0

160

384

0

16

1

nfs_page

0

200

96

0

5

1

ip_fib_hash

10

113

32

1

1

1

journal_head

51

7020

48

2

90

1

revoke_table

2

253

12

1

1

1

revoke_record

0

0

32

0

0

1

clip_arp_cache

0

0

128

0

0

1

ip_mrt_cache

0

0

96

0

0

1

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.

Note that active in this case means an object is in use. Therefore an active object is one that is in use,

and an active slab is one that contains one or more active object.

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 to 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.