/proc/meminfo

[mahiapkum]

can anyone help me with detailed explanation of cat /proc/meminfo and cat /proc/iomem command:
MemTotal: 1018132 kB
MemFree: 597464 kB
Buffers: 20220 kB
Cached: 197856 kB
SwapCached: 0 kB
Active: 243500 kB
Inactive: 121264 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 1018132 kB
LowFree: 597464 kB
SwapTotal: 2048248 kB
SwapFree: 2048248 kB
Dirty: 884 kB
Writeback: 0 kB
Mapped: 192916 kB
Slab: 32680 kB
Committed_AS: 329560 kB
PageTables: 7044 kB
VmallocTotal: 536870911 kB
VmallocUsed: 264172 kB
VmallocChunk: 536606655 kB
HugePages_Total: 0
HugePages_Free: 0
Hugepagesize: 2048 kB

00000000-0009fbff : System RAM
0009fc00-0009ffff : reserved
000a0000-000bffff : Video RAM area
000c0000-000c7fff : Video ROM
000f0000-000fffff : System ROM
00100000-3f72f7ff : System RAM
00100000-002fbcb8 : Kernel code
002fbcb9-0043361b : Kernel data
3f72f800-3f72ffff : ACPI Non-volatile Storage
3f730000-3f73ffff : ACPI Tables
3f740000-3f7effff : ACPI Non-volatile Storage
3f7f0000-3f7fffff : reserved
cfb00000-cfbfffff : PCI Bus #05
cfc00000-cfcfffff : PCI Bus #04
cfd00000-cfdfffff : PCI Bus #03
cfe00000-cfefffff : PCI Bus #02
cff00000-cfffffff : PCI Bus #01
d0000000-dfffffff : 0000:00:02.0
e0000000-efffffff : reserved
fed13000-fed19fff : reserved
fed1c000-fed9ffff : reserved
ff33fc00-ff33ffff : 0000:00:1d.7
ff33fc00-ff33ffff : ehci_hcd
ff340000-ff37ffff : 0000:00:02.0
ff380000-ff3fffff : 0000:00:02.0
ff400000-ff4fffff : 0000:06:01.0
ff400000-ff402fff : CS46xx_BA1_data0
ff410000-ff4137ff : CS46xx_BA1_data1
ff420000-ff426fff : CS46xx_BA1_pmem
ff430000-ff4300ff : CS46xx_BA1_reg
ff500000-ff500fff : 0000:06:01.0
ff500000-ff500fff : CS46xx_BA0
ff501000-ff501fff : 0000:06:08.0
ff501000-ff501fff : e100
ff600000-ff6fffff : PCI Bus #05
ff700000-ff7fffff : PCI Bus #04
ff800000-ff8fffff : PCI Bus #03
ff900000-ff9fffff : PCI Bus #02
ffa00000-ffafffff : PCI Bus #01

[svlsr2000]

Under linux all data's are stored as files. you might be familiar with two types of file systems i.e. binary files and text files.

In linux there is one more type of files called virtual file system. /proc/ containts these virtual files, hence /proc/ is also called as virtual file system.

Though (Most of the time) the size of these files are zero, but whe these files are read using cat, less or more they give lot of informations.


cat /proc/meminfo":

root: total: used: free: shared: buffers: cached:Mem: 1055760384 1041887232 13873152 0 100417536 711233536Swap: 1077501952 8540160 1068961792 MemTotal: 1031016 kB MemFree: 13548 kBMemShared: 0 kBBuffers: 98064 kBCached: 692320 kBSwapCached: 2244 kBActive: 563112 kBInact_dirty: 309584 kBInact_clean: 79508 kBInact_target: 190440 kBHighTotal: 130992 kBHighFree: 1876 kBLowTotal: 900024 kBLowFree: 11672 kBSwapTotal: 1052248 kBSwapFree: 1043908 kBCommitted_AS: 332340 kBAt top we can see some of the values which users usually peopleare keen on.MemTotal: Total usable ram (i.e. physical ram minus a few reserved bits and the kernel binary code)

MemFree: Is sum of LowFree+HighFree (overall stat)

MemShared: 0; is here for compat reasons but always zero.

Buffers: Memory in buffer cache. mostly useless as metric nowadays

Cached: Memory in the pagecache (diskcache) minus SwapCache

SwapCache: Memory that once was swapped out, is swapped back in but still also is in the swapfile (if memory is needed it doesn't need to be swapped out AGAIN because it is already in the swapfile. This saves I/O)