Linux Process Memory Footprint view command

(1) Top mission

The code is as follows	Copy Code
$ top-u Oracle

1. Top command

The code is as follows	Copy Code
top-d 1-p pid [, pid ...]//set to delay 1s, default is delay 3s

If you want to sort by memory usage, you can shift + m (sort by memory usage)

(2) Pmap

You can view the memory usage of process-related information based on the process (the process number can be viewed through PS) as follows:

The code is as follows	Copy Code
$ pmap-d 14596

(3) PS
　　
As shown in the following example:

The code is as follows	Copy Code
$ ps-e-O ' pid,comm,args,pcpu,rsz,vsz,stime,user,uid ' where Rsz is the actual memory $ ps-e-o ' pid,comm,args,pcpu,rsz,vsz,stime,user,uid ' |  grep Oracle | Sort-nrk5

Where Rsz is the actual memory, the above example realizes by memory sort, from big to small

Static view of memory usage for a process

1, Pmap command

The code is as follows	Copy Code
Pmap PID

2. PS command

The code is as follows	Copy Code
PS Aux|grep process_name

3, view the status file under the/proc/process_id/folder

The code is as follows

Copy Code

name:php State:r (running) sleepavg:0% tgid:21574 pid:21574 ppid:10005 tracerpid:0 uid:1000 1000 1000 1000 GID:100 100 100 100 fdsize:256 Groups:16 100 vmpeak:161740 KB vmsize:161740 KB vmlck:0 KB vmhwm:107144 KB vmrss:107144 KB vmdata:106192 KB vmstk:84 KB vmexe:5588 KB vmlib:7884 KB vmpte:268 KB Threads:1 sigq:0/69632 sigpnd:0000000000000000 shdpnd:0000000000000000 sigblk:0000000000000000 sigign:0000000000001000 Sigcgt:00000001818040a7 capinh:0000000000000000 capprm:0000000000000000 capeff:0000000000000000 cpus_allowed:00000000,00000000,00000000,0000000f Mems_allowed:1

The size of the task virtual address space Vmsize
The size of the physical memory the application is using Vmrss

View memory We generally use the free command:

The code is as follows	Copy Code
[root@scs-2 tmp]# Free              total        used       free     shared    buffers     Cached mem:       3266180    3250004      16176          0      110652    2668236 -/+ buffers/cache:     471116     2795064 swap:      2048276      80160     1968116

The following is an explanation of these values:
Total: The amount of physical memory.
Used: How big it has been used.
Free: How many are available.
Shared: The total amount of memory shared by multiple processes.
Buffers/cached: The size of the disk cache.
Third line (-/+ buffers/cached):
Used: How big it has been used.
Free: How many are available.
The line four is not much explained.
Difference: The difference between the used/free of the second line (MEM) and the used/free of the third row (-/+ Buffers/cache). The difference between the two is that the first line is from the OS point of view, because for os,buffers/cached is used, so his available memory is 16176KB, the used memory is 3250004KB, which includes, the kernel (OS) uses + Application (X, oracle,etc) used by +buffers+cached.
The third line refers to the application from the point of view of the application, buffers/cached is equal to available, because buffer/cached is to improve the performance of file read, when the application needs to use memory, the buffer/cached will be quickly recycled.

Measurement of memory footprint

Measuring how much memory a process consumes, Linux provides us with a convenient way, the/proc directory provides us with all the information, in fact, top and other tools to get the appropriate information.

The code is as follows	Copy Code
Memory usage information for/proc/meminfo machines The/proc/pid/maps PID is the process number that displays the virtual address occupied by the current process. Memory consumed by the/PROC/PID/STATM process [Root@localhost ~]# CAT/PROC/SELF/STATM 654 57 44 0 0 334 0

Output explanation

CPU and CPU0 ... The meaning of each parameter (in the first act) of each row is:

Parameter Interpretation/proc//status

The code is as follows

Copy Code

Size (pages) task virtual address space VMSIZE/4 The size of the physical memory that the resident (pages) application is using VMRSS/4 Shared (pages) share pages 0 The size of the executable virtual memory owned by the TRS (pages) program VMEXE/4 Lrs (pages) the size of the library that is imaged to the virtual memory space of the task VMLIB/4 Drs (pages) program data segment and user state stack size (vmdata+ VMSTK) 4 DT (pages) 04

View Machine available memory

The code is as follows	Copy Code
/proc/28248/>free Total used free shared buffers Cached mem:1023788 926400 97388 0 134668 503688 -/+ buffers/cache:288044 735744 swap:1959920 89608 1870312

When we look at the idle memory of the machine by using the free command, we find that the value of the freed is very small. This is mainly because, in Linux, there is such a thought, not white memory, so it as much as possible cache and buffer some data to facilitate the next use. But in fact, these memory can also be used immediately.

So free memory =free+buffers+cached=total-used