How to check memory usage per process in Linux
https://www.golinuxcloud.com/check-memory-usage-per-process-linux/#:~:text=There%20are%20several%20metrics%20available%20to%20check%20memory,sum%20of%20all%20the%20regions%20shown%20in%20%2Fproc%2F%3CPID%3E%2Fmap.
Table of Contents
- Using top and ps to check memory usage per process (VSS and RSS)
- Using smem to check memory usage per process
Linux check memory usage per process. how to check which process is using more memory in Linux. Linux how much memory is a process using. Linux track process memory usage over time. linux check memory usage per process in mb. Linux check memory. linux show memory usage. linux see memory usage. linux memory usage info. linux process memory usage. how to check memory usage in linux.
There are several metrics available to check memory usage per process in Linux. I will begin with the two that are easiest to obtain
- the virtual set size (vss)
- the resident memory size (rss)
both of which are available in most implementations of the ps and top commands.
-
Vss: called
VSZin thepscommand and VIRT intop, is the total amount of memory mapped by a process. It is the sum of all the regions shown in/proc/<PID>/map. This number is of limited interest, since only part of the virtual memory is committed to physical memory at any one time. -
Rss: called
RSSinpsandRESintop, is the sum of memory that is mapped to physical pages of memory. This gets closer to the actual memory budget of the process, but there is a problem, if you add up theRssof all the processes, you will get an overestimate the memory in use because some pages will be shared.
ALSO READ:
A detailed overview on Linux memory management and different types on memory in Linux
Using top and ps to check memory usage per process (VSS and RSS)
The ps command shows Vss (VSZ) and Rss (RSS) with the options, -Aly, and a custom format which includes vsz and rss, as shown here
# ps -eo pid,tid,class,rtprio,stat,vsz,rss,comm PID TID CLS RTPRIO STAT VSZ RSS COMMAND 1283 1283 TS - S<sl 59636 1116 auditd 1337 1337 TS - Ssl 476848 9996 NetworkManager 1366 1366 TS - Ssl 553488 13196 polkitd 1456 1456 TS - S 267684 31768 sssd_nss 1617 1617 TS - Ss+ 116376 872 agetty 2955 2955 TS - Ss 93728 2236 master 4843 4843 TS - Ss 156356 5156 sshd
Likewise free and top also shows a summary of the free memory and memory usage per process:
# free -m
total used free shared buff/cache available
Mem: 128814 7603 52253 153 68957 120183
Swap: 4091 0 4091
NOTE:
These simple commands give you a feel of the memory usage and give the first indication that you have a memory leak when you see that the Rss of a process keeps on increasing. However, they are not very accurate in the absolute measurements of memory usage.
Using smem to check memory usage per process
In 2009, Matt Mackall began looking at the problem of accounting for shared pages in process memory measurement and added two new metrics called the unique set size or Uss, and the proportional set size or Pss
- Uss: This is the amount of memory that is committed to physical memory and is unique to a process; it is not shared with any other. It is the amount of memory that would be freed if the process were to terminate.
-
Pss: This splits the accounting of shared pages that are committed to physical memory between all the processes that have them mapped. For example, if an area of library code is 12 pages long and is shared by six processes, each will accumulate two pages in
Pss. Thus, if you add thePssnumbers for all processes, you will get the actual amount of memory being used by those processes. In other words,Pssis the number we have been looking for.
ALSO READ:
Shell script to check top memory & cpu consuming process in Linux
The information is available in /proc/<PID>/smaps, which contains additional information for each of the mappings shown in /proc/<PID>/maps. Here is one section from such a file which provides information about the mapping for the libc code segment:
# cat /proc/31768/smaps | grep -i pss Pss: 1132 kB Pss: 4 kB Pss: 44 kB Pss: 48 kB Pss: 54632 kB Pss: 1 kB << Output trimmed >> Pss: 0 kB Pss: 0 kB Pss: 4 kB Pss: 4 kB Pss: 4 kB Pss: 0 kB
# cat /proc/31768/smaps | grep -i pss | awk '{Total+=$2} END {print Total/1024" MB"}'
56.4102 MB
# cat /proc/31768/smaps | grep -i rss | awk '{Total+=$2} END {print Total/1024" MB"}'
58.7109 MB
NOTE:
Note that the Rss is 58.7 M but because it is shared between many other processes, the Pss is only 56.4 MB.
There is a tool named smem that collates the information from the smaps files and presents it in various ways, including as pie or bar charts. The project page for smem is https://www.selenic.com/smem.
There are various filters which you can apply with smem as shown below with the latest available release (1.4) at the time of writing this article
# ./smem --help
Usage: smem [options]
Options:
-h, --help show this help message and exit
-H, --no-header disable header line
-c COLUMNS, --columns=COLUMNS
columns to show
-t, --totals show totals
-R REALMEM, --realmem=REALMEM
amount of physical RAM
-K KERNEL, --kernel=KERNEL
path to kernel image
-m, --mappings show mappings
-u, --users show users
-w, --system show whole system
-P PROCESSFILTER, --processfilter=PROCESSFILTER
process filter regex
-M MAPFILTER, --mapfilter=MAPFILTER
map filter regex
-U USERFILTER, --userfilter=USERFILTER
user filter regex
-n, --numeric numeric output
-s SORT, --sort=SORT field to sort on
-r, --reverse reverse sort
-p, --percent show percentage
-k, --abbreviate show unit suffixes
--pie=PIE show pie graph
--bar=BAR show bar graph
-S SOURCE, --source=SOURCE
/proc data source
To check memory usage per process in total we can execute below command
# ./smem -t -k PID User Command Swap USS PSS RSS 5496 ssrun ssRelay -pidfile /opt/mgtse 0 112.0K 152.0K 460.0K 5522 ssrun ssProbeframework -pidfile / 0 116.0K 156.0K 464.0K 2072 root rhnsd 0 172.0K 194.0K 616.0K 2013 root /usr/bin/rhsmcertd 0 172.0K 195.0K 684.0K 1617 root /sbin/agetty --noclear tty1 0 184.0K 196.0K 876.0K 1493 root /usr/sbin/atd -f 0 260.0K 271.0K 1.1M 22058 root /usr/sbin/rpc.idmapd 0 380.0K 384.0K 676.0K 7802 root /usr/sbin/xinetd -stayalive 0 396.0K 408.0K 1.1M << Output trimmed >> 10901 rpc /sbin/rpcbind -w 0 608.0K 655.0K 1.4M 11885 oamsys -bash 0 524.0K 739.0K 2.2M 4847 oamsys -bash 0 528.0K 743.0K 2.2M 2008 root /usr/sbin/oddjobd -n -p /va 0 632.0K 764.0K 1.9M 22202 sufuser /usr/sbin/httpd -DFOREGROUN 0 372.0K 768.0K 5.4M 22203 sufuser /usr/sbin/httpd -DFOREGROUN 0 372.0K 768.0K 5.4M 27326 sufuser /usr/sbin/httpd -DFOREGROUN 0 372.0K 768.0K 5.4M 22199 sufuser /usr/sbin/httpd -DFOREGROUN 0 372.0K 769.0K 5.4M 27327 sufuser /usr/sbin/httpd -DFOREGROUN 0 372.0K 769.0K 5.4M 22201 sufuser /usr/sbin/httpd -DFOREGROUN 0 380.0K 775.0K 5.4M 22200 sufuser /usr/sbin/httpd -DFOREGROUN 0 380.0K 776.0K 5.4M 12096 root -bash 0 580.0K 809.0K 2.3M 7989 ntp /usr/sbin/ntpd -u ntp:ntp - 0 780.0K 814.0K 1.7M 11564 oamsys /usr/libexec/openssh/sftp-s 0 744.0K 834.0K 2.4M 5523 ssrun ssProbeframework -pidfile / 0 185.3M 191.3M 198.4M ------------------------------------------------------------------------------- 93 11 0 1.9G 2.0G 2.1G
This will give you memory usage detail of every process active on your system.
To get the memory usage of a single process we can grep the process from the list
# ./smem -k | sed -e '1p' -e '/amsHelper/!d' | grep -v sed PID User Command Swap USS PSS RSS 31768 root /sbin/amsHelper -f 0 56.0M 56.4M 58.7M
Here as you see we get similar results as above with /proc/31768/smaps and with smem tool. So the actual memory usage of amsHelper is 56.4 MB
Lastly I hope the steps from the article to check memory usage per process on Linux was helpful. So, let me know your suggestions and feedback using the comment section.