3.2. Top-level Files within the proc File System
Below is a list of some of the more useful virtual files in the top-level of the /proc/ directory.
In most cases, the content of the files listed in this
section are not the same as those installed on your
machine. This is because much of the information is specific
to the hardware on which Red Hat Enterprise Linux is running
for this documentation effort.
This file provides information about the state of the
Advanced Power Management (APM) system
and is used by the apm
command. If a system with no battery is connected to an AC
power source, this virtual file would look similar to the
1.16 1.2 0x07 0x01 0xff 0x80 -1% -1 ?
Running the apm -v command
on such a system results in output similar to the following:
APM BIOS 1.2 (kernel driver 1.16ac) AC on-line, no system battery
For systems which do not use a battery as a power source,
apm is able do little more
than put the machine in standby mode. The apm command is much more useful on
laptops. For example, the following output is from the
command cat /proc/apm on a
laptop while plugged into a power outlet:
1.16 1.2 0x03 0x01 0x03 0x09 100% -1 ?
When the same laptop is unplugged from its power source for a
few minutes, the content of the apm file changes to something like
1.16 1.2 0x03 0x00 0x00 0x01 99% 1792 min
The apm -v command now
yields more useful data, such as the following:
APM BIOS 1.2 (kernel driver 1.16) AC off-line, battery status high: 99% (1 day, 5:52)
This file is used primarily for diagnosing memory
fragmentation issues. Using the buddy algorithm, each column
represents the number of pages of a certain order (a certain
size) that are available at any given time. For example, for
zone DMA (direct memory access), there are 90 of
2^(0*PAGE_SIZE) chunks of memory. Similarly, there are 6 of
2^(1*PAGE_SIZE) chunks, and 2 of 2^(2*PAGE_SIZE) chunks of
The DMA row references
the first 16 MB on a system, the HighMem row references all memory
greater than 4 GB on a system, and the Normal row references all memory
The following is an example of the output typical of
Node 0, zone DMA 90 6 2 1 1 ...
Node 0, zone Normal 1650 310 5 0 0 ...
Node 0, zone HighMem 2 0 0 1 1 ...
This file shows the parameters passed to the kernel at the
time it is started. A sample /proc/cmdline file looks like the
ro root=/dev/VolGroup00/LogVol00 rhgb quiet 3
This tells us that the kernel is mounted read-only (signified
located on the first logical volume (LogVol00) of the first
volume group (/dev/VolGroup00). LogVol00 is the equivalent
of a disk partition in a non-LVM system (Logical Volume
Management), just as /dev/VolGroup00 is similar
in concept to /dev/hda1,
but much more extensible.
For more information on LVM used in Red Hat Enterprise Linux,
refer to http://www.tldp.org/HOWTO/LVM-HOWTO/index.html.
signals that the rhgb
package has been installed, and graphical booting is
supported, assuming /etc/inittab shows a default
runlevel set to id:5:initdefault:.
Finally, quiet indicates all verbose
kernel messages are suppressed at boot time.
This virtual file identifies the type of processor used by
your system. The following is an example of the output
typical of /proc/cpuinfo:
processor : 0
vendor_id : GenuineIntel
cpu family : 15
model : 2
model name : Intel(R) Xeon(TM) CPU 2.40GHz
stepping : 7 cpu
MHz : 2392.371
cache size : 512 KB
physical id : 0
siblings : 2
runqueue : 0
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm
bogomips : 4771.02
Provides each processor with an identifying number. On
systems that have one processor, only a 0 is present.
family — Authoritatively
identifies the type of processor in the system. For an
Intel-based system, place the number in front of "86" to
determine the value. This is particularly helpful for
those attempting to identify the architecture of an
older system such as a 586, 486, or 386. Because some
RPM packages are compiled for each of these particular
architectures, this value also helps users determine
which packages to install.
name — Displays the common name
of the processor, including its project name.
— Shows the precise speed in megahertz for the
processor to the thousandths decimal place.
size — Displays the amount of
level 2 memory cache available to the processor.
Displays the number of sibling CPUs on the same physical
CPU for architectures which use hyper-threading.
— Defines a number of different qualities about
the processor, such as the presence of a floating point
unit (FPU) and the ability to process MMX instructions.
This file lists all installed cryptographic ciphers used by
the Linux kernel, including additional details for each. A
sample /proc/crypto file
looks like the following:
name : sha1
module : kernel
type : digest
blocksize : 64
digestsize : 20
name : md5
module : md5
type : digest
blocksize : 64
digestsize : 16
This file displays the various character and block devices
currently configured (not including devices whose modules are
not loaded). Below is a sample output from this file:
The output from /proc/devices includes the major
number and name of the device, and is broken into two major
devices and Block devices.
Character devices are similar to
block devices, except for two basic
Character devices do not require buffering. Block devices
have a buffer available, allowing them to order requests
before addressing them. This is important for devices
designed to store information — such as hard drives
— because the ability to order the information
before writing it to the device allows it to be placed in
a more efficient order.
Character devices send data with no preconfigured
size. Block devices can send and receive information in
blocks of a size configured per device.
For more information about devices refer to the following
This file contains a list of the registered ISA DMA channels
in use. A sample /proc/dma files looks like the
This file lists the execution domains
currently supported by the Linux kernel, along with the range
of personalities they support.
0-0 Linux [kernel]
Think of execution domains as the "personality" for an
operating system. Because other binary formats, such as
Solaris, UnixWare, and FreeBSD, can be used with Linux,
programmers can change the way the operating system treats
system calls from these binaries by changing the personality
of the task. Except for the PER_LINUX execution domain,
different personalities can be implemented as dynamically
This file contains a list of frame buffer devices, with the
frame buffer device number and the driver that controls
it. Typical output of /proc/fb for systems which contain
frame buffer devices looks similar to the following:
0 VESA VGA
This file displays a list of the file system types currently
supported by the kernel. Sample output from a generic
looks similar to the following:
The first column signifies whether the file system is mounted
on a block device. Those beginning with nodev are not mounted on a
device. The second column lists the names of the file systems
The mount command cycles
through the file systems listed here when one is not
specified as an argument.
This file records the number of interrupts per IRQ on the x86
architecture. A standard /proc/interrupts looks similar to
0: 80448940 XT-PIC timer
1: 174412 XT-PIC keyboard
2: 0 XT-PIC cascade
8: 1 XT-PIC rtc
10: 410964 XT-PIC eth0
12: 60330 XT-PIC PS/2 Mouse
14: 1314121 XT-PIC ide0
15: 5195422 XT-PIC ide1
For a multi-processor machine, this file may look slightly
0: 1366814704 0 XT-PIC timer
1: 128 340 IO-APIC-edge keyboard
2: 0 0 XT-PIC cascade
8: 0 1 IO-APIC-edge rtc
12: 5323 5793 IO-APIC-edge PS/2 Mouse
13: 1 0 XT-PIC fpu
16: 11184294 15940594 IO-APIC-level Intel EtherExpress Pro 10/100 Ethernet
20: 8450043 11120093 IO-APIC-level megaraid
30: 10432 10722 IO-APIC-level aic7xxx
31: 23 22 IO-APIC-level aic7xxx
The first column refers to the IRQ number. Each CPU in the
system has its own column and its own number of interrupts
per IRQ. The next column reports the type of interrupt, and
the last column contains the name of the device that is
located at that IRQ.
Each of the types of interrupts seen in this file, which
are architecture-specific, mean something different. For
x86 machines, the following values are common:
— This is the old AT computer interrupts.
The voltage signal on this interrupt transitions from
low to high, creating an edge,
where the interrupt occurs and is only signaled
once. This kind of interrupt, as well as the
interrupt, are only seen on systems with processors
from the 586 family and higher.
Generates interrupts when its voltage signal is high
until the signal is low again.
This file shows you the current map of the system's memory
for each physical device:
00000000-0009fbff : System RAM
0009fc00-0009ffff : reserved
000a0000-000bffff : Video RAM area
000c0000-000c7fff : Video ROM
000f0000-000fffff : System ROM
00100000-07ffffff : System RAM
00100000-00291ba8 : Kernel code
00291ba9-002e09cb : Kernel data
e0000000-e3ffffff : VIA Technologies, Inc. VT82C597 [Apollo VP3] e4000000-e7ffffff : PCI Bus #01
e4000000-e4003fff : Matrox Graphics, Inc. MGA G200 AGP
e5000000-e57fffff : Matrox Graphics, Inc. MGA G200 AGP
e8000000-e8ffffff : PCI Bus #01
e8000000-e8ffffff : Matrox Graphics, Inc. MGA G200 AGP
ea000000-ea00007f : Digital Equipment Corporation DECchip 21140 [FasterNet]
ea000000-ea00007f : tulip ffff0000-ffffffff : reserved
The first column displays the memory registers used by each
of the different types of memory. The second column lists the
kind of memory located within those registers and displays
which memory registers are used by the kernel within the
system RAM or, if the network interface card has multiple
Ethernet ports, the memory registers assigned for each port.
The output of /proc/ioports provides a list of
currently registered port regions used for input or output
communication with a device. This file can be quite long. The
following is a partial listing:
0000-001f : dma1
0020-003f : pic1
0040-005f : timer
0060-006f : keyboard
0070-007f : rtc
0080-008f : dma page reg
00a0-00bf : pic2
00c0-00df : dma2
00f0-00ff : fpu
0170-0177 : ide1
01f0-01f7 : ide0
02f8-02ff : serial(auto)
0376-0376 : ide1
03c0-03df : vga+
03f6-03f6 : ide0
03f8-03ff : serial(auto)
0cf8-0cff : PCI conf1
d000-dfff : PCI Bus #01
e000-e00f : VIA Technologies, Inc. Bus Master IDE
e000-e007 : ide0
e008-e00f : ide1
e800-e87f : Digital Equipment Corporation DECchip 21140 [FasterNet]
e800-e87f : tulip
The first column gives the I/O port address range reserved
for the device listed in the second column.
This file represents the physical memory of the system and is
stored in the core file format. Unlike most /proc/ files, kcore displays a size. This value
is given in bytes and is equal to the size of the physical
memory (RAM) used plus 4 KB.
The contents of this file are designed to be examined by a
debugger, such as gdb, and
is not human readable.
Do not view the /proc/kcore virtual file. The
contents of the file scramble text output on the
terminal. If this file is accidentally viewed, press
to stop the process and then type reset to bring back the command
This file is used to hold messages generated by the
kernel. These messages are then picked up by other programs,
such as /sbin/klogd or
This file provides a look at the load average in regard to
both the CPU and IO over time, as well as additional data
used by uptime and other
commands. A sample /proc/loadavg file looks similar
to the following:
0.20 0.18 0.12 1/80 11206
The first three columns measure CPU and IO utilization of the
last one, five, and 10 minute periods. The fourth column
shows the number of currently running processes and the total
number of processes. The last column displays the last
process ID used.
This file displays the files currently locked by the
kernel. The contents of this file contain internal kernel
debugging data and can vary tremendously, depending on the
use of the system. A sample /proc/locks file for a lightly
loaded system looks similar to the following:
1: POSIX ADVISORY WRITE 3568 fd:00:2531452 0 EOF
2: FLOCK ADVISORY WRITE 3517 fd:00:2531448 0 EOF
3: POSIX ADVISORY WRITE 3452 fd:00:2531442 0 EOF
4: POSIX ADVISORY WRITE 3443 fd:00:2531440 0 EOF
5: POSIX ADVISORY WRITE 3326 fd:00:2531430 0 EOF
6: POSIX ADVISORY WRITE 3175 fd:00:2531425 0 EOF
7: POSIX ADVISORY WRITE 3056 fd:00:2548663 0 EOF
Each lock has its own line which starts with a unique
number. The second column refers to the class of lock used,
signifying the older-style UNIX file locks from a flock system call and
representing the newer POSIX locks from the lockf system call.
The third column can have two values: ADVISORY or MANDATORY. ADVISORY means that the lock
does not prevent other people from accessing the data; it
only prevents other attempts to lock it. MANDATORY means that no
other access to the data is permitted while the lock is
held. The fourth column reveals whether the lock is allowing
the holder READ or WRITE access to the
file. The fifth column shows the ID of the process holding
the lock. The sixth column shows the ID of the file being
locked, in the format of MAJOR-DEVICE:MINOR-DEVICE:INODE-NUMBER. The
seventh and eighth column shows the start and end of the
file's locked region.
This file contains the current information for multiple-disk,
RAID configurations. If the system does not contain such a
configuration, then /proc/mdstat looks similar to the
Personalities : read_ahead not set unused devices: <none>
This file remains in the same state as seen above unless a
software RAID or md
device is present. In that case, view /proc/mdstat to find the current
status of mdX
The /proc/mdstat file
below shows a system with its md0 configured as a RAID 1 device,
while it is currently re-syncing the disks:
Personalities : [linear] [raid1] read_ahead 1024 sectors
md0: active raid1 sda2 sdb2 9940 blocks [2/2] [UU] resync=1% finish=12.3min algorithm 2 [3/3] [UUU]
unused devices: <none>
This is one of the more commonly used files in the /proc/ directory, as it reports a
large amount of valuable information about the systems RAM
The following sample /proc/meminfo virtual file is from
a system with 256 MB of RAM and 512 MB of swap space:
MemTotal: 255908 kB
MemFree: 69936 kB
Buffers: 15812 kB
Cached: 115124 kB
SwapCached: 0 kB
Active: 92700 kB
Inactive: 63792 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 255908 kB
LowFree: 69936 kB
SwapTotal: 524280 kB
SwapFree: 524280 kB
Dirty: 4 kB
Writeback: 0 kB
Mapped: 42236 kB
Slab: 25912 kB
Committed_AS: 118680 kB
PageTables: 1236 kB
VmallocTotal: 3874808 kB
VmallocUsed: 1416 kB
VmallocChunk: 3872908 kB
Hugepagesize: 4096 kB
Much of the information here is used by the free, top, and ps commands. In fact, the output of
the free command is
similar in appearance to the contents and structure of
/proc/meminfo. But by
looking directly at /proc/meminfo, more details are
— Total amount of physical RAM, in kilobytes.
— The amount of physical RAM, in kilobytes, left
unused by the system.
— The amount of physical RAM, in kilobytes, used
for file buffers.
— The amount of physical RAM, in kilobytes, used as
SwapCached — The
amount of swap, in kilobytes, used as cache memory.
— The total amount of buffer or page cache memory,
in kilobytes, that is in active use. This is memory that
has been recently used and is usually not reclaimed for
— The total amount of buffer or page cache memory,
in kilobytes, that are free and available. This is memory
that has not been recently used and can be reclaimed for
— The total and free amount of memory, in
kilobytes, that is not directly mapped into kernel
space. The HighTotal value can vary
based on the type of kernel used.
and LowFree — The
total and free amount of memory, in kilobytes, that is
directly mapped into kernel space. The LowTotal value can vary
based on the type of kernel used.
SwapTotal — The
total amount of swap available, in kilobytes.
— The total amount of swap free, in kilobytes.
— The total amount of memory, in kilobytes, waiting
to be written back to the disk.
Writeback — The
total amount of memory, in kilobytes, actively being
written back to the disk.
— The total amount of memory, in kilobytes, which
have been used to map devices, files, or libraries using
the mmap command.
— The total amount of memory, in kilobytes, used by
the kernel to cache data structures for its own use.
Committed_AS — The
total amount of memory, in kilobytes, estimated to
complete the workload. This value represents the worst
case scenario value, and also includes swap memory.
PageTables — The
total amount of memory, in kilobytes, dedicated to the
lowest page table level.
VMallocTotal — The
total amount of memory, in kilobytes, of total allocated
virtual address space.
VMallocUsed — The
total amount of memory, in kilobytes, of used virtual
VMallocChunk — The
largest contiguous block of memory, in kilobytes, of
available virtual address space.
The total number of hugepages for the system. The number
is derived by dividing Hugepagesize by the
megabytes set aside for hugepages specified in /proc/sys/vm/hugetlb_pool. This
statistic only appears on the x86, Itanium, and AMD64
The total number of hugepages available for the
system. This statistic only appears on the x86,
Itanium, and AMD64 architectures.
Hugepagesize — The
size for each hugepages unit in kilobytes. By default,
the value is 4096 KB on uniprocessor kernels for 32 bit
architectures. For SMP, hugemem kernels, and AMD64, the
default is 2048 KB. For Itanium architectures, the
default is 262144 KB. This statistic only
appears on the x86, Itanium, and AMD64
This file lists miscellaneous drivers registered on the
miscellaneous major device, which is device number 10:
63 device-mapper 175 agpgart 135 rtc 134 apm_bios
The first column is the minor number of each device, while
the second column shows the driver in use.
This file displays a list of all modules loaded into the
kernel. Its contents vary based on the configuration and use
of your system, but it should be organized in a similar
manner to this sample /proc/modules file output:
This example has been reformatted into a readable
format. Most of this information can also be viewed via the
nfs 170109 0 - Live 0x129b0000
lockd 51593 1 nfs, Live 0x128b0000
nls_utf8 1729 0 - Live 0x12830000
vfat 12097 0 - Live 0x12823000
fat 38881 1 vfat, Live 0x1287b000
autofs4 20293 2 - Live 0x1284f000
sunrpc 140453 3 nfs,lockd, Live 0x12954000
3c59x 33257 0 - Live 0x12871000
uhci_hcd 28377 0 - Live 0x12869000
md5 3777 1 - Live 0x1282c000
ipv6 211845 16 - Live 0x128de000
ext3 92585 2 - Live 0x12886000
jbd 65625 1 ext3, Live 0x12857000
dm_mod 46677 3 - Live 0x12833000
The first column contains the name of the module.
The second column refers to the memory size of the module, in
The third column lists how many instances of the module are
currently loaded. A value of zero represents an unloaded
The fourth column states if the module depends upon another
module to be present in order to function, and lists those
The fifth column lists what load state the module is in:
Live, Loading, or Unloading are the only possible
The sixth column lists the current kernel memory offset for
the loaded module. This information can be useful for
debugging purposes, or for profiling tools such as oprofile.
This file provides a list of all mounts in use by the system:
rootfs / rootfs rw 0 0
/proc /proc proc rw,nodiratime 0 0 none
/dev ramfs rw 0 0
/dev/mapper/VolGroup00-LogVol00 / ext3 rw 0 0
none /dev ramfs rw 0 0
/proc /proc proc rw,nodiratime 0 0
/sys /sys sysfs rw 0 0
none /dev/pts devpts rw 0 0
usbdevfs /proc/bus/usb usbdevfs rw 0 0
/dev/hda1 /boot ext3 rw 0 0
none /dev/shm tmpfs rw 0 0
none /proc/sys/fs/binfmt_misc binfmt_misc rw 0 0
sunrpc /var/lib/nfs/rpc_pipefs rpc_pipefs rw 0 0
The output found here is similar to the contents of /etc/mtab, except that /proc/mount is more up-to-date.
The first column specifies the device that is mounted, the
second column reveals the mount point, and the third column
tells the file system type, and the fourth column tells you
if it is mounted read-only (ro) or read-write
fifth and sixth columns are dummy values designed to match
the format used in /etc/mtab.
This file refers to the current Memory Type Range Registers
(MTRRs) in use with the system. If the system architecture
supports MTRRs, then the /proc/mtrr file may look similar
to the following:
reg00: base=0x00000000 ( 0MB), size= 256MB: write-back, count=1
reg01: base=0xe8000000 (3712MB), size= 32MB: write-combining, count=1
MTRRs are used with the Intel P6 family of processors
(Pentium II and higher) and control processor access to
memory ranges. When using a video card on a PCI or AGP bus, a
properly configured /proc/mtrr file can increase
performance more than 150%.
Most of the time, this value is properly configured by
default. More information on manually configuring this file
can be found locally at the following location:
This file contains partition block allocation information. A
sampling of this file from a basic system looks similar to
major minor #blocks name
3 0 19531250 hda
3 1 104391 hda1
3 2 19422585 hda2
253 0 22708224 dm-0
253 1 524288 dm-1
Most of the information here is of little importance to the
user, except for the following columns:
— The major number of the device with this
partition. The major number in the /proc/partitions,
corresponds with the block device ide0, in /proc/devices.
— The minor number of the device with this
partition. This serves to separate the partitions into
different physical devices and relates to the number at
the end of the name of the partition.
— Lists the number of physical disk blocks
contained in a particular partition.
— The name of the partition.
This file contains a full listing of every PCI device on the
system. Depending on the number of PCI devices, /proc/pci can be rather long. A
sampling of this file from a basic system looks similar to
Bus 0, device 0, function 0: Host bridge: Intel Corporation 440BX/ZX - 82443BX/ZX Host bridge (rev 3). Master Capable. Latency=64. Prefetchable 32 bit memory at 0xe4000000 [0xe7ffffff].
Bus 0, device 1, function 0: PCI bridge: Intel Corporation 440BX/ZX - 82443BX/ZX AGP bridge (rev 3). Master Capable. Latency=64. Min Gnt=128.
Bus 0, device 4, function 0: ISA bridge: Intel Corporation 82371AB PIIX4 ISA (rev 2).
Bus 0, device 4, function 1: IDE interface: Intel Corporation 82371AB PIIX4 IDE (rev 1). Master Capable. Latency=32. I/O at 0xd800 [0xd80f].
Bus 0, device 4, function 2: USB Controller: Intel Corporation 82371AB PIIX4 USB (rev 1). IRQ 5. Master Capable. Latency=32. I/O at 0xd400 [0xd41f].
Bus 0, device 4, function 3: Bridge: Intel Corporation 82371AB PIIX4 ACPI (rev 2). IRQ 9.
Bus 0, device 9, function 0: Ethernet controller: Lite-On Communications Inc LNE100TX (rev 33). IRQ 5. Master Capable. Latency=32. I/O at 0xd000 [0xd0ff].
Bus 0, device 12, function 0: VGA compatible controller: S3 Inc. ViRGE/DX or /GX (rev 1). IRQ 11. Master Capable. Latency=32. Min Gnt=4.Max Lat=255.
This output shows a list of all PCI devices, sorted in the
order of bus, device, and function. Beyond providing the
name and version of the device, this list also gives
detailed IRQ information so an administrator can quickly
look for conflicts.
To get a more readable version of this information, type:
This file gives full information about memory usage on the
slab level. Linux kernels greater than
version 2.2 use slab pools to manage
memory above the page level. Commonly used objects have their
own slab pools.
Instead of parsing the highly verbose /proc/slabinfo file manually, the
displays kernel slab cache information in real time. This
program allows for custom configurations, including column
sorting and screen refreshing.
A sample screen shot of /usr/bin/slabtop usually looks
like the following example:
Active / Total Objects (% used) : 133629 / 147300 (90.7%)
Active / Total Slabs (% used) : 11492 / 11493 (100.0%)
Active / Total Caches (% used) : 77 / 121 (63.6%)
Active / Total Size (% used) : 41739.83K / 44081.89K (94.7%)
Minimum / Average / Maximum Object : 0.01K / 0.30K / 128.00K
OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
44814 43159 96% 0.62K 7469 6 29876K ext3_inode_cache
36900 34614 93% 0.05K 492 75 1968K buffer_head
35213 33124 94% 0.16K 1531 23 6124K dentry_cache
7364 6463 87% 0.27K 526 14 2104K radix_tree_node
2585 1781 68% 0.08K 55 47 220K vm_area_struct
2263 2116 93% 0.12K 73 31 292K size-128
1904 1125 59% 0.03K 16 119 64K size-32
1666 768 46% 0.03K 14 119 56K anon_vma
1512 1482 98% 0.44K 168 9 672K inode_cache
1464 1040 71% 0.06K 24 61 96K size-64
1320 820 62% 0.19K 66 20 264K filp
678 587 86% 0.02K 3 226 12K dm_io
678 587 86% 0.02K 3 226 12K dm_tio
576 574 99% 0.47K 72 8 288K proc_inode_cache
528 514 97% 0.50K 66 8 264K size-512
492 372 75% 0.09K 12 41 48K bio
465 314 67% 0.25K 31 15 124K size-256
452 331 73% 0.02K 2 226 8K biovec-1
420 420 100% 0.19K 21 20 84K skbuff_head_cache
305 256 83% 0.06K 5 61 20K biovec-4
290 4 1% 0.01K 1 290 4K revoke_table
264 264 100% 4.00K 264 1 1056K size-4096
260 256 98% 0.19K 13 20 52K biovec-16
260 256 98% 0.75K 52 5 208K biovec-64
Some of the more commonly used statistics in /proc/slabinfo that are included
— The total number of objects (memory blocks),
including those in use (allocated), and some spares not
— The number of objects (memory blocks) that are
in use (allocated).
— Percentage of total objects that are
SIZE — The size of the objects.
— The total number of slabs.
OBJ/SLAB — The
number of objects that fit into a slab.
SIZE — The cache size of the
— The name of the slab.
For more information on the /usr/bin/slabtop program, refer
to the slabtop man
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, usually begins like the following
cpu 259246 7001 60190 34250993 137517 772 0
cpu0 259246 7001 60190 34250993 137517 772 0
intr 354133732 347209999 2272 0 4 4 0 0 3 1 1249247 0 0 80143 0 422626 5169433
cpu 209841 1554 21720 118519346 72939 154 27168
cpu0 42536 798 4841 14790880 14778 124 3117
cpu1 24184 569 3875 14794524 30209 29 3130
cpu2 28616 11 2182 14818198 4020 1 3493
cpu3 35350 6 2942 14811519 3045 0 3659
cpu4 18209 135 2263 14820076 12465 0 3373
cpu5 20795 35 1866 14825701 4508 0 3615
cpu6 21607 0 2201 14827053 2325 0 3334
cpu7 18544 0 1550 14831395 1589 0 3447
intr 15239682 14857833 6 0 6 6 0 5 0 1 0 0 0 29 0 2 0 0 0 0 0 0 0 94982 0 286812
Some of the more commonly used statistics include:
— Measures the number of
jiffies (1/100 of a second for
x86 systems) that the system has been in user mode, user
mode with low priority (nice), system mode, idle task,
I/O wait, IRQ (hardirq), and softirq respectively. The
IRQ (hardirq) is the direct response to a hardware
event. The IRQ takes minimal work for queuing the
"heavy" work up for the softirq to execute. The softirq
runs at a lower priority than the IRQ and therefore may
be interrupted more frequently. The total for all CPUs
is given at the top, while each individual CPU is listed
below with its own statistics. The following example is
a 4-way Intel Pentium Xeon configuration with
multi-threading enabled, therefore showing four physical
processors and four virtual processors totaling eight
— The number of memory pages the system has
written in and out to disk.
— The number of swap pages the system has brought
in and out.
— The number of interrupts the system has
— The boot time, measured in the number of seconds
since January 1, 1970, otherwise known as the
This file measures swap space and its utilization. For a
system with only one swap partition, the output of /proc/swaps may look similar to
Filename Type Size Used Priority
/dev/mapper/VolGroup00-LogVol01 partition 524280 0 -1
While some of this information can be found in other files
in the /proc/
provides a snapshot of every swap file name, the type of
swap space, the total size, and the amount of space in use
(in kilobytes). The priority column is useful when multiple
swap files are in use. The lower the priority, the more
likely the swap file is to be used.
Using the echo command to
write to this file, a remote root user can execute most
System Request Key commands remotely as if at the local
terminal. To echo values
to this file, the /proc/sys/kernel/sysrq must be
set to a value other than 0. For more information
about the System Request Key, refer to Section 18.104.22.168, “/proc/sys/kernel/”.
Although it is possible to write to this file, it cannot be
read, even by the root user.
This file contains information detailing how long the system
has been on since its last restart. The output of /proc/uptime is quite minimal:
The first number is the total number of seconds the system
has been up. The second number is how much of that time the
machine has spent idle, in seconds.
This file specifies the version of the Linux kernel and
gcc in use, as well as
the version of Red Hat Enterprise Linux installed on the
Linux version 2.6.8-1.523 ([email protected]) (gcc version 3.4.1 20040714 \ (Red Hat Enterprise Linux 3.4.1-7)) #1 Mon Aug 16 13:27:03 EDT 2004
This information is used for a variety of purposes,
including the version data presented when a user logs in.