linux内存学习
1.vmstat
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
1 0 750568 298464 232836 1440800 1 1 4 5 5 18 4 7 87 1
vmstat -a
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r b swpd free inact active si so bi bo in cs us sy id wa
3 0 748720 261968 1347780 1250832 1 1 4 5 6 19 4 7 87 1
procs:
r:The number of processes waiting for run time.
b:The number of processes in uninterruptible sleep.
Memory:
swpd:the amount of swapped memory used. =/proc/meminfo中的Swaptotal -Swapfree.
free:the amount of idle memory.=/proc/meminfo中的Memfree
buffer:the amount of memory used as buffers.
cache:the amount of memory used as cache.
inact:the amount of inactive memory.
active:the amount of active memory.
swap:
si: Amount of memory swapped in from disk (/s).单位为KB
so:Amount of memory swapped to disk (/s).
IO:
bi:Blocks received from a block device (blocks/s).
bo:Blocks sent to a block device (blocks/s).
system:
in: The number of interrupts per second, including the clock.
cs: The number of context switches per second.
CPU:
us:Time spent running non-kernel code.(user time , including the clock)
sy:Time spent running kernel code.(system time)
id:Time spent idle.Prior to Linux 2.5.41, this includes IO-wait time.
wa:Time spent waiting for IO.Prior to Linux 2.5.41, included in idle.
st:Time stolen from a virtual machine.Prior to Linux 2.6.11, unkown.
2.free
free
total used free shared buffers cached
Mem: 4081868 3833076 248792 0 200816 1575716
-/+ buffers/cache: 2056544 2025324
Swap: 4094972 740156 3354816
total:总计物理内存的大小
used:已使用多大.
free:可用有多少.
shared:多个进程共享内存总额.
Buffers/cached:磁盘缓存的大小.
这里着重讲一下mem的used/free与-/+ buffers/cache的used/free的区别.它们的区别主要是从观察的角度来看:
mem是从OS的角度,对于OS,buffers/cached都属于被使用,所以可用内存是248792KB,已用内存是3833076 KB,其中包括内核使用+Application(X,postgres,etc) 使用的+buffers+cached;
-/+ buffers/cache是从应用程序的角度:可用内存=系统free memory+buffers+cached.上例中free2025324=248792+200816+1575716
所以机器的物理内存free的值很小,这是因为,在linux中有这么一种思想,内存不用白不用,因此它尽可能的cache和buffer一些数据,以方便下次使用.但实际这些内存也可以直接拿来使用的.
3./proc/下的东东
(1)/proc/meminfo
MemTotal: 4081868 kB ---total usable physical ram
MemFree: 191436 kB ---sum of LowFree and High Free of physical ram.
Buffers: 300408 kB---The amount of physical RAM used for file buffers
Cached: 1522444 kB---The amount of physical RAM used as cache memory
SwapCached: 170456 kB---The amount of swap used as cache memory.The swap cache is similar in concept to the page cache.
Active: 1317960 kB---total amount of buffer or page cache memory that is in active use.
Inactive: 1354336 kB---total amount of buffer or page cache memory that are free and available.
Active(anon): 409912 kB
Inactive(anon): 441508 kB
Active(file): 908048 kB
Inactive(file): 912828 kB
Unevictable: 16 kB
Mlocked: 16 kB
HighTotal: 3237336 kB---total and free amount of memory that is not directly mapped into kernel space
HighFree: 94236 kB
LowTotal: 844532 kB---total and free amount of memory that is directly mapped into kernel space
LowFree: 97200 kB
SwapTotal: 4094972 kB---total amount of swap available.
SwapFree: 3352716 kB---total amount of swap free.
Dirty: 3856 kB---total amount of memory, waiting to be written back to the disk.
Writeback: 0 kB---total amount of memory actively being written back to the disk.
AnonPages: 775216 kB
Mapped: 1128872 kB---The total amount of memory, which have been used to map devices, files, or libraries using the mmap command.All "Mapped:" memory is "Cached", but not all "Cached:" memory is "Mapped:". The first time the mmap area is acessed, the page will be brought in from the disk and mapped into memory.
Shmem: 1976 kB
Slab: 134180 kB---total amount of memory used by the kernel to cache data structures for its own use.
SReclaimable: 108112 kB---the recliamable memory of slab.
SUnreclaim: 26068 kB
KernelStack: 4552 kB
PageTables: 15876 kB---the total amount of memory dedicated to the lowest page table level.管理内存分页页面的索引表的大小.
NFS_Unstable: 0 kB---不稳定页表的大小.
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 6135904 kB---based on the overcommit ratio('vm.overcommit_ratio'),this is the total amount of memory currently available to be allocated on the system.This limit is only adhered to if strict overcommit acounting is enabled(mode 2 in 'vm.overcommit_memory').The Commit limit is calculated with the following formula:CommitLimit=('vm.overcommit_ratio'*Physical RAM)+Swap.
Committed_AS: 5440204 kB---the total amount of memory estimated to complete the workload.This value represents the worst case scennario value, and also includes swap memory.
VmallocTotal: 122880 kB---the total amount of memory of total allocated virtual address space.
VmallocUsed: 86444 kB---the total amount of memory of used virtual address space.
VmallocChunk: 17432 kB---the largetst contiguous block of memory of avalible virtual address space.
HardwareCorrupted: 0 kB
AnonHugePages: 0 kB
HugePages_Total: 0---the total number of hugepages for the system.
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB---the size for each hugepages .4096KB on uniprocessor kernels for 32 bit architectures.For SMP, hugemem kenels, and AMD64, the default is 2048 KB.
DirectMap4k: 206840 kB
DirectMap2M: 706560 kB
(2)/proc/pid/maps 进程所占用的虚拟地址
cat /proc/1164/maps
08048000-08375000 r-xp 00000000 fd:01 873683 /usr/local/pgsql/bin/postgres
08375000-0837e000 rw-p 0032c000 fd:01 873683 /usr/local/pgsql/bin/postgres
0837e000-083e7000 rw-p 0837e000 00:00 0 [heap]
5dd2a000-7769c000 rw-s 00000000 00:08 16089088 /SYSV0052e2c1 (deleted)
7769c000-776a4000 r-xp 00000000 fd:00 36924 /lib/libnss_files.so.2
776a4000-776a6000 rw-p 00007000 fd:00 36924 /lib/libnss_files.so.2
776a6000-776b7000 r-xp 00000000 fd:00 36916 /lib/libnsl.so.1
776b7000-776b9000 rw-p 00010000 fd:00 36916 /lib/libnsl.so.1
776b9000-776bb000 rw-p 776b9000 00:00 0
776bb000-776c1000 r-xp 00000000 fd:00 36888 /lib/libnss_compat.so.2
776c1000-776c3000 rw-p 00006000 fd:00 36888 /lib/libnss_compat.so.2
776c3000-776c4000 rw-p 776c3000 00:00 0
776c4000-777d2000 r-xp 00000000 fd:00 36920 /lib/libc.so.6
777d2000-777d3000 r--p 0010e000 fd:00 36920 /lib/libc.so.6
777d3000-777d6000 rw-p 0010f000 fd:00 36920 /lib/libc.so.6
777d6000-777d8000 rw-p 777d6000 00:00 0
777d8000-777f8000 r-xp 00000000 fd:00 36903 /lib/libm.so.6
777f8000-777fa000 rw-p 00020000 fd:00 36903 /lib/libm.so.6
777fa000-777fc000 r-xp 00000000 fd:00 36904 /lib/libdl.so.2
777fc000-777fe000 rw-p 00001000 fd:00 36904 /lib/libdl.so.2
777fe000-77802000 r-xp 00000000 fd:00 36885 /lib/libcrypt.so.1
77802000-77804000 rw-p 00004000 fd:00 36885 /lib/libcrypt.so.1
77804000-7782c000 rw-p 77804000 00:00 0
7782e000-77843000 r-xp 00000000 fd:00 36894 /lib/ld-linux.so.2
77843000-77844000 r--p 00014000 fd:00 36894 /lib/ld-linux.so.2
77844000-77845000 rw-p 00015000 fd:00 36894 /lib/ld-linux.so.2
7f896000-7f8ab000 rw-p 7ffeb000 00:00 0 [stack]
ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
(3)/proc/pid/statm 进程所占用的虚拟内存
cat /proc/1164/statm
106189 3902 3824 813 0 171 0
man 5 proc,搜statm,provides infomation about memory usage, measured in pages.
size total program size(same as VmSize in /proc/[pid]/status)
used resident set size(same as VmRSS in /proc/[pid]/status)常驻内存空间页大小
shared shared pages(from shared mappings)
text text(code) (same as exe in /proc/[pid]/status)
lib library(unused in Linux 2.6q)(same as vmLib in /proc/[pid]/status)
data data+stack(same as vmData+vmStack in /proc/[pid]/status)
dt dirty pages(unused in Linux 2.6)
(4)/proc/pid/status
cat /proc/1164/status
Name: postgres
State: S (sleeping)
Tgid: 1164
Pid: 1164
PPid: 1
TracerPid: 0
Uid: 70 70 70 70
Gid: 70 70 70 70
FDSize: 1024
Groups: 70
VmPeak: 424760 kB
VmSize: 424756 kB
VmLck: 0 kB
VmHWM: 17056 kB
VmRSS: 15608 kB
VmData: 600 kB
VmStk: 84 kB
VmExe: 3252 kB
VmLib: 1440 kB
VmPTE: 60 kB
Threads: 1
SigQ: 0/69632
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000001303000
SigCgt: 0000000000014a07
CapInh: 00000000fffffeff
CapPrm: 0000000000000000
CapEff: 0000000000000000
CapBnd: ffffffffffffffff
voluntary_ctxt_switches: 8726984
nonvoluntary_ctxt_switches: 1159326
