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417 lines
18 KiB
Markdown
[#]: collector: (lujun9972)
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[#]: translator: ( )
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (8 Commands to Check Memory Usage on Linux)
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[#]: via: (https://www.2daygeek.com/linux-commands-check-memory-usage/)
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[#]: author: (Magesh Maruthamuthu https://www.2daygeek.com/author/magesh/)
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8 Commands to Check Memory Usage on Linux
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======
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Linux is not like Windows and you will not get a GUI always, especially in a server environment.
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As a Linux administrator, it is important to know how to check your available and used resources, such as memory, CPU, disk space, etc.
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If there are any applications that use too much resources on the system to run your system at the optimum level you need to find and fix.
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If you want to **[find out the top 10 memory (RAM) consumption processes in Linux][1]**, go to the following article.
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In Linux, there are commands for everything, so use the corresponding commands.
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In this tutorial, we will show you eight powerful commands to check memory usage on a Linux system, including RAM and swap.
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**[Creating swap space on a Linux system][2]** is very important.
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The following commands can help you check memory usage in Linux in different ways.
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* free Command
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* /proc/meminfo File
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* vmstat Command
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* ps_mem Command
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* smem Command
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* top Command
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* htop Command
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* glances Command
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### 1) How to Check Memory Usage on Linux Using the free Command
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**[Free command][3]** is the most powerful command widely used by the Linux administrator. But it provides very little information compared to the “/proc/meminfo” file.
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Free command displays the total amount of free and used physical and swap memory on the system, as well as buffers and caches used by the kernel.
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These information is gathered from the “/proc/meminfo” file.
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```
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# free -m
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total used free shared buff/cache available
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Mem: 15867 9199 1702 3315 4965 3039
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Swap: 17454 666 16788
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```
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* **total:** Total installed memory
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* **used:** Memory is currently in use by running processes (used= total – free – buff/cache)
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* **free:** Unused memory (free= total – used – buff/cache)
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* **shared:** Memory shared between two or more processes (multiple processes)
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* **buffers:** Memory reserved by the kernel to hold a process queue request.
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* **cache:** Size of the page cache that holds recently used files in RAM
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* **buff/cache:** Buffers + Cache
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* **available:** Estimation of how much memory is available for starting new applications, without swapping.
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### 2) How to Check Memory Usage on Linux Using the /proc/meminfo File
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The “/proc/meminfo” file is a virtual file that contains various real-time information about memory usage.
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It shows memory stats in kilobytes, most of which are somewhat difficult to understand.
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However it contains useful information about memory usage.
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```
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# cat /proc/meminfo
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MemTotal: 16248572 kB
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MemFree: 1764576 kB
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MemAvailable: 3136604 kB
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Buffers: 234132 kB
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Cached: 4731288 kB
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SwapCached: 28516 kB
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Active: 9004412 kB
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Inactive: 3552416 kB
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Active(anon): 8094128 kB
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Inactive(anon): 2896064 kB
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Active(file): 910284 kB
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Inactive(file): 656352 kB
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Unevictable: 80 kB
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Mlocked: 80 kB
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SwapTotal: 17873388 kB
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SwapFree: 17191328 kB
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Dirty: 252 kB
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Writeback: 0 kB
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AnonPages: 7566736 kB
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Mapped: 3692368 kB
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Shmem: 3398784 kB
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Slab: 278976 kB
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SReclaimable: 125480 kB
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SUnreclaim: 153496 kB
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KernelStack: 23936 kB
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PageTables: 73880 kB
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NFS_Unstable: 0 kB
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Bounce: 0 kB
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WritebackTmp: 0 kB
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CommitLimit: 25997672 kB
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Committed_AS: 24816804 kB
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VmallocTotal: 34359738367 kB
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VmallocUsed: 0 kB
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VmallocChunk: 0 kB
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Percpu: 3392 kB
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HardwareCorrupted: 0 kB
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AnonHugePages: 0 kB
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ShmemHugePages: 0 kB
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ShmemPmdMapped: 0 kB
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HugePages_Total: 0
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HugePages_Free: 0
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HugePages_Rsvd: 0
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HugePages_Surp: 0
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Hugepagesize: 2048 kB
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Hugetlb: 0 kB
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DirectMap4k: 1059088 kB
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DirectMap2M: 14493696 kB
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DirectMap1G: 2097152 kB
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```
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### 3) How to Check Memory Usage on Linux Using the vmstat Command
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The **[vmstat command][4]** is another useful tool for reporting virtual memory statistics.
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vmstat reports information about processes, memory, paging, block IO, traps, disks, and cpu functionality.
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vmstat does not require special permissions, and it can help identify system bottlenecks.
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```
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# vmstat
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procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
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r b swpd free buff cache si so bi bo in cs us sy id wa st
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1 0 682060 1769324 234188 4853500 0 3 25 91 31 16 34 13 52 0 0
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```
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If you want to understand this in detail, read the field description below.
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**Procs**
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* **r:** The number of runnable processes (running or waiting for run time).
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* **b:** The number of processes in uninterruptible sleep.
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**Memory**
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* **swpd:** the amount of virtual memory used.
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* **free:** the amount of idle memory.
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* **buff:** the amount of memory used as buffers.
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* **cache:** the amount of memory used as cache.
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* **inact:** the amount of inactive memory. (-a option)
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* **active:** the amount of active memory. (-a option)
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**Swap**
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* **si:** Amount of memory swapped in from disk (/s).
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* **so:** Amount of memory swapped to disk (/s).
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**IO**
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* **bi:** Blocks received from a block device (blocks/s).
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* **bo:** Blocks sent to a block device (blocks/s).
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**System**
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* **in:** The number of interrupts per second, including the clock.
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* **cs:** The number of context switches per second.
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**CPU : These are percentages of total CPU time.**
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* **us:** Time spent running non-kernel code. (user time, including nice time)
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* **sy:** Time spent running kernel code. (system time)
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* **id:** Time spent idle. Prior to Linux 2.5.41, this includes IO-wait time.
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* **wa:** Time spent waiting for IO. Prior to Linux 2.5.41, included in idle.
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* **st:** Time stolen from a virtual machine. Prior to Linux 2.6.11, unknown.
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Run the following command for detailed information.
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```
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# vmstat -s
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16248580 K total memory
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2210256 K used memory
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2311820 K active memory
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2153352 K inactive memory
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11368812 K free memory
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107584 K buffer memory
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2561928 K swap cache
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17873388 K total swap
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0 K used swap
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17873388 K free swap
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44309 non-nice user cpu ticks
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164 nice user cpu ticks
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14332 system cpu ticks
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382418 idle cpu ticks
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1248 IO-wait cpu ticks
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1407 IRQ cpu ticks
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2147 softirq cpu ticks
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0 stolen cpu ticks
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1022437 pages paged in
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260296 pages paged out
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0 pages swapped in
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0 pages swapped out
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1424838 interrupts
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4979524 CPU context switches
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1577163147 boot time
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3318 forks
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```
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### 4) How to Check Memory Usage on Linux Using the ps_mem Command
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**[ps_mem][5]** is a simple Python script that allows you to get core memory usage accurately for a program in Linux.
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This can determine how much RAM is used per program (not per process).
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It calculates the total amount of memory used per program, total = sum (private RAM for program processes) + sum (shared RAM for program processes).
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The shared RAM is problematic to calculate, and the tool automatically selects the most accurate method available for the running kernel.
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```
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# ps_mem
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Private + Shared = RAM used Program
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180.0 KiB + 30.0 KiB = 210.0 KiB xf86-video-intel-backlight-helper (2)
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192.0 KiB + 66.0 KiB = 258.0 KiB cat (2)
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312.0 KiB + 38.5 KiB = 350.5 KiB lvmetad
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380.0 KiB + 25.5 KiB = 405.5 KiB crond
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392.0 KiB + 32.5 KiB = 424.5 KiB rtkit-daemon
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852.0 KiB + 117.0 KiB = 969.0 KiB gnome-session-ctl (2)
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928.0 KiB + 56.5 KiB = 984.5 KiB gvfs-mtp-volume-monitor
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1.0 MiB + 42.5 KiB = 1.0 MiB dconf-service
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1.0 MiB + 106.5 KiB = 1.1 MiB gvfs-goa-volume-monitor
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1.0 MiB + 180.5 KiB = 1.2 MiB gvfsd
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.
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.
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5.3 MiB + 3.0 MiB = 8.3 MiB evolution-addressbook-factory
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8.5 MiB + 1.2 MiB = 9.7 MiB gnome-session-binary (4)
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7.5 MiB + 3.1 MiB = 10.5 MiB polkitd
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7.4 MiB + 3.3 MiB = 10.7 MiB pulseaudio (2)
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7.0 MiB + 7.0 MiB = 14.0 MiB msm_notifier
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12.7 MiB + 2.3 MiB = 15.0 MiB evolution-source-registry
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13.3 MiB + 2.5 MiB = 15.8 MiB gnome-terminal-server
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15.8 MiB + 1.0 MiB = 16.8 MiB tracker-miner-fs
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18.7 MiB + 1.8 MiB = 20.5 MiB python3.7
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16.6 MiB + 4.0 MiB = 20.5 MiB evolution-calendar-factory
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22.3 MiB + 753.0 KiB = 23.0 MiB gsd-keyboard (2)
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22.4 MiB + 832.0 KiB = 23.2 MiB gsd-wacom (2)
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20.8 MiB + 2.5 MiB = 23.3 MiB blueman-tray
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22.0 MiB + 1.8 MiB = 23.8 MiB blueman-applet
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23.1 MiB + 934.0 KiB = 24.0 MiB gsd-xsettings (2)
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23.7 MiB + 1.2 MiB = 24.9 MiB gsd-media-keys (2)
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23.4 MiB + 1.6 MiB = 25.0 MiB gsd-color (2)
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23.9 MiB + 1.2 MiB = 25.1 MiB gsd-power (2)
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16.5 MiB + 8.9 MiB = 25.4 MiB evolution-alarm-notify
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27.2 MiB + 2.0 MiB = 29.2 MiB systemd-journald
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28.7 MiB + 2.8 MiB = 31.5 MiB c
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29.6 MiB + 2.2 MiB = 31.8 MiB chrome-gnome-sh (2)
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43.9 MiB + 6.8 MiB = 50.7 MiB WebExtensions
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46.7 MiB + 6.7 MiB = 53.5 MiB goa-daemon
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86.5 MiB + 55.2 MiB = 141.7 MiB Xorg (2)
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191.4 MiB + 24.1 MiB = 215.4 MiB notepadqq-bin
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306.7 MiB + 29.0 MiB = 335.7 MiB gnome-shell (2)
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601.6 MiB + 77.7 MiB = 679.2 MiB firefox
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1.0 GiB + 109.7 MiB = 1.1 GiB chrome (15)
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2.3 GiB + 123.1 MiB = 2.5 GiB Web Content (8)
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----------------------------------
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5.6 GiB
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==================================
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```
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### 5) How to Check Memory Usage on Linux Using the smem Command
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**[smem][6]** is a tool that can provide numerous reports of memory usage on Linux systems. Unlike existing tools, smem can report Proportional Set Size (PSS), Unique Set Size (USS) and Resident Set Size (RSS).
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Proportional Set Size (PSS): refers to the amount of memory used by libraries and applications in the virtual memory system.
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Unique Set Size (USS) : Unshared memory is reported as USS (Unique Set Size).
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Resident Set Size (RSS) : The standard measure of physical memory (it typically shared among multiple applications) usage known as resident set size (RSS) will significantly overestimate memory usage.
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```
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# smem -tk
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PID User Command Swap USS PSS RSS
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3383 daygeek cat 0 92.0K 123.0K 1.7M
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3384 daygeek cat 0 100.0K 129.0K 1.7M
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1177 daygeek /usr/lib/gnome-session-ctl 0 436.0K 476.0K 4.6M
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1171 daygeek /usr/bin/dbus-daemon --conf 0 524.0K 629.0K 3.8M
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1238 daygeek /usr/lib/xdg-permission-sto 0 592.0K 681.0K 5.9M
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1350 daygeek /usr/lib/gsd-screensaver-pr 0 652.0K 701.0K 5.8M
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1135 daygeek /usr/lib/gdm-x-session --ru 0 648.0K 723.0K 6.0M
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.
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.
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1391 daygeek /usr/lib/evolution-data-ser 0 16.5M 25.2M 63.3M
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1416 daygeek caffeine-ng 0 28.7M 31.4M 66.2M
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4855 daygeek /opt/google/chrome/chrome - 0 38.3M 46.3M 120.6M
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2174 daygeek /usr/lib/firefox/firefox -c 0 44.0M 50.7M 120.3M
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1254 daygeek /usr/lib/goa-daemon 0 46.7M 53.3M 80.4M
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3416 daygeek /opt/google/chrome/chrome - 0 44.7M 54.2M 103.3M
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4782 daygeek /opt/google/chrome/chrome - 0 57.2M 65.8M 142.3M
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1137 daygeek /usr/lib/Xorg vt2 -displayf 0 77.2M 129.6M 192.3M
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3376 daygeek /opt/google/chrome/chrome 0 117.8M 131.0M 210.9M
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4448 daygeek /usr/lib/firefox/firefox -c 0 124.4M 133.8M 224.1M
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3558 daygeek /opt/google/chrome/chrome - 0 157.3M 165.7M 242.2M
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2310 daygeek /usr/lib/firefox/firefox -c 0 159.6M 169.4M 259.6M
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4331 daygeek /usr/lib/firefox/firefox -c 0 176.8M 186.2M 276.8M
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4034 daygeek /opt/google/chrome/chrome - 0 179.3M 187.9M 264.6M
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3911 daygeek /opt/google/chrome/chrome - 0 183.1M 191.8M 269.4M
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3861 daygeek /opt/google/chrome/chrome - 0 199.8M 208.2M 285.2M
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2746 daygeek /usr/bin/../lib/notepadqq/n 0 193.5M 217.5M 261.5M
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1194 daygeek /usr/bin/gnome-shell 0 203.7M 219.0M 285.1M
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2945 daygeek /usr/lib/firefox/firefox -c 0 294.5M 308.0M 410.2M
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2786 daygeek /usr/lib/firefox/firefox -c 0 341.2M 354.3M 459.1M
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4193 daygeek /usr/lib/firefox/firefox -c 0 417.4M 427.6M 519.3M
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2651 daygeek /usr/lib/firefox/firefox -c 0 417.0M 430.1M 535.6M
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2114 daygeek /usr/lib/firefox/firefox -c 0 430.6M 473.9M 610.9M
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2039 daygeek /usr/lib/firefox/firefox -- 0 601.3M 677.5M 840.6M
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-------------------------------------------------------------------------------
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90 1 0 4.8G 5.2G 8.0G
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```
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### 6) How to Check Memory Usage on Linux Using the top Command
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**[top command][7]** is one of the most frequently used commands by Linux administrators to understand and view the resource usage for a process on a Linux system.
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It displays the total memory of the system, current memory usage, free memory and total memory used by the buffers.
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In addition, it displays total swap memory, current swap usage, free swap memory, and total cached memory by the system.
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```
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# top -b | head -10
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top - 11:04:39 up 40 min, 1 user, load average: 1.59, 1.42, 1.28
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Tasks: 288 total, 2 running, 286 sleeping, 0 stopped, 0 zombie
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%Cpu(s): 13.3 us, 1.5 sy, 0.0 ni, 84.4 id, 0.0 wa, 0.3 hi, 0.5 si, 0.0 st
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KiB Mem : 16248572 total, 7755928 free, 4657736 used, 3834908 buff/cache
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KiB Swap: 17873388 total, 17873388 free, 0 used. 9179772 avail Mem
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PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
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2114 daygeek 20 3182736 616624 328228 R 83.3 3.8 7:09.72 Web Content
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2039 daygeek 20 4437952 849616 261364 S 13.3 5.2 7:58.54 firefox
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1194 daygeek 20 4046856 291288 165460 S 4.2 1.8 1:57.68 gnome-shell
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4034 daygeek 20 808556 273244 88676 S 4.2 1.7 1:44.72 chrome
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2945 daygeek 20 3309832 416572 150112 S 3.3 2.6 4:04.60 Web Content
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1137 daygeek 20 564316 197292 183380 S 2.5 1.2 2:55.76 Xorg
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2651 daygeek 20 3098420 547260 275700 S 1.7 3.4 2:15.96 Web Content
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2786 daygeek 20 2957112 463912 240744 S 1.7 2.9 3:22.29 Web Content
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1 root 20 182756 10208 7760 S 0.8 0.1 0:04.51 systemd
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442 root -51 S 0.8 0:05.02 irq/141-iw+
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1426 daygeek 20 373660 48948 29820 S 0.8 0.3 0:03.55 python3
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2174 daygeek 20 2466680 122196 78604 S 0.8 0.8 0:17.75 WebExtensi+
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```
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### 7) How to Check Memory Usage on Linux Using the htop Command
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The **[htop command][8]** is an interactive process viewer for Linux/Unix systems. It is a text-mode application and requires the ncurses library, it was developed by Hisham.
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It is designed as an alternative to the top command.
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This is similar to the top command, but allows you to scroll vertically and horizontally to see all the processes running the system.
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htop comes with Visual Colors, which have added benefits and are very evident when it comes to tracking system performance.
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You are free to carry out any tasks related to processes, such as process killing and renicing without entering their PIDs.
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[![][9]][10]
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### 8) How to Check Memory Usage on Linux Using the glances Command
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**[Glances][11]** is a cross-platform system monitoring tool written in Python.
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You can see all information in one place such as CPU usage, Memory usage, running process, Network interface, Disk I/O, Raid, Sensors, Filesystem info, Docker, System info, Uptime, etc,.
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![][9]
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--------------------------------------------------------------------------------
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via: https://www.2daygeek.com/linux-commands-check-memory-usage/
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作者：[Magesh Maruthamuthu][a]
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选题：[lujun9972][b]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://www.2daygeek.com/author/magesh/
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[b]: https://github.com/lujun9972
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[1]: https://www.2daygeek.com/how-to-find-high-cpu-consumption-processes-in-linux/
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[2]: https://www.2daygeek.com/add-extend-increase-swap-space-memory-file-partition-linux/
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[3]: https://www.2daygeek.com/free-command-to-check-memory-usage-statistics-in-linux/
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[4]: https://www.2daygeek.com/linux-vmstat-command-examples-tool-report-virtual-memory-statistics/
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[5]: https://www.2daygeek.com/ps_mem-report-core-memory-usage-accurately-in-linux/
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[6]: https://www.2daygeek.com/smem-linux-memory-usage-statistics-reporting-tool/
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[7]: https://www.2daygeek.com/linux-top-command-linux-system-performance-monitoring-tool/
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[8]: https://www.2daygeek.com/linux-htop-command-linux-system-performance-resource-monitoring-tool/
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[9]: data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
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[10]: https://www.2daygeek.com/wp-content/uploads/2019/12/linux-commands-check-memory-usage-2.jpg
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[11]: https://www.2daygeek.com/linux-glances-advanced-real-time-linux-system-performance-monitoring-tool/
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