free command: display memory usage and the system is idle, including physical memory, interaction zone memory (the swap) and the kernel buffer memory.
[root@ipha-dev71-1 workspace]# free # kb total used free shared buff/cache available Mem: 16251672 13033660 254336 45824 2963676 2630624 Swap: 16777212 31512 16745700 [root@ipha-dev71-1 workspace]# free -m # MB total used free shared buff/cache available Mem: 15870 12728 248 44 2894 2569 Swap: 16383 30 16353 [@ IPha the root -dev71- . 1 Workspace] # Free - H # -H automatically selected to suit the capacity of the unit display appreciated Total Used Free Shared BUFF / Cache Available Mem: 248M 44M. 15G. 12G 2 0.8 g 2 .5 g Swap: 15G 15G 30M
Mem: represents the physical memory statistics, the remaining memory if the machine is very small, typically less than 20% of the total memory, it is determined that the system is not enough physical memory Swap: exchange of usage indicates partition on the hard disk, such as a small remaining space, the current system requires attention load and memory usage, when the value of the used Swap is greater than 0, then the operating system is not enough physical memory, a hard disk memory has started. Line 1 represents the total physical memory data 11G; 6.5G indicates a total allocated to the buffer (containing buffers and cache) the number of use, but may not actually use the cache portion; 1.3G represents unallocated memory; shared Shared represents memory; 4.0G system represents the number of buffers allocated but unused; 4.7G system represents the number of allocated but unused available
top command: view real-time load on the system, including processes, CPU load, memory usage, and so on;
[root@ipha-dev71-1 workspace]# top top - 20:15:25 up 23 days, 22:27, 2 users, load average: 0.01, 0.03, 0.05 Tasks: 173 total, 2 running, 171 sleeping, 0 stopped, 0 zombie %Cpu(s): 0.1 us, 0.1 sy, 0.0 ni, 99.8 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem : 16251672 total, 253612 free, 13034008 used, 2964052 buff/cache KiB Swap: 16777212 total, 16745700 free, 31512 used. 2630252 avail Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 46001 root 20 0 7575660 1.140g 16224 S 0.7 7.4 21:30.36 java 3616 root 20 0 5552312 151452 4008 S 0.3 0.9 93:50.14 beam.smp 46490 root 20 0 8365988 2.075g 16164 S 0.3 13.4 11:18.42 java 48345 root 20 0 8808752 2.448g 20224 S 0.3 15.8 34:00.03 java 78331 root 20 0 6818552 565924 11448 S 0.3 3.5 14:32.37 java 1 root 20 0 191288 3312 2124 S 0.0 0.0 0:51.12 systemd 2 root 20 0 0 0 0 S 0.0 0.0 0:00.33 kthreadd 3 root 20 0 0 0 0 S 0.0 0.0 0:00.53 ksoftirqd/0 5 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/0:0H 7 root rt 0 0 0 0 S 0.0 0.0 0:00.08 migration/0 8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcu_bh 9 root 20 0 0 0 0 S 0.0 0.0 5:57.72 rcu_sched 10 root rt 0 0 0 0 S 0.0 0.0 0:04.27 watchdog/0
11 root rt 0 0 0 0 S 0.0 0.0 0:03.38 watchdog/1 12 root rt 0 0 0 0 S 0.0 0.0 0:02.14 migration/1