Embedded Files
Memory/Swap Information
Memory/Swap Information
Linux/UNIX will use free RAM for things like disk caching. This artificially elevates the “used” memory figure and reduces the “free” memory figure. The RAM used as disk cache is flagged as both “used” and “available” because it can be very easily reclaimed at any time.
free
free -m
free -mt
free -gt
Show figures in KB
Show figures in MB
Show figures in MB with Totals
Show figures in GB with Totals
Example output from free... total used free shared buff/cache availableMem: 61580608 42263196 1706948 3940240 17610464 13240884Swap: 16777212 174308 16602904
This output from free shows that the system has a total of 61,580,608K of memory, of which 42,263,196K is considered used. This used figure includes 17,610,464K of OS buffers/caches and 3,940,240K of shared memory. The available memory is calculated based on some additional information (available from /proc/zoneinfo and /proc/meminfo).
See the awk script below for a reproduction of the internal available memory calculation (adapted from Stephen Kitt via unix.stackexchange)... zi=/proc/zoneinfomi=/proc/meminfoawk -v low=$(grep low ${zi}|awk '{k+=$2}END{print k}') \ '{a[$1]=$2} END{ print a["MemFree:"]+a["Active(file):"]+a["Inactive(file):"]+a["SReclaimable:"]-(12*low); }' ${mi}
Keeping available memory at around 20% of total memory is a good rule of thumb (but remember every rule of thumb has its exceptions). You can calculate your current percentage using...
awk '{a[$1]=$2} END{ print a["MemAvailable:"]/a["MemTotal:"]*100; }' /proc/meminfo
prtconf -m
Example output from prtconf -mMemory Size: 32768 MB
svmon -G
size inuse free pin virtual mmodememory 2490368 1661688 828680 524156 601823 Dedpg space 2490368 3796
work pers clnt otherpin 439364 0 3656 81136in use 601823 0 1059865
PageSize PoolSize inuse pgsp pin virtuals 4 KB - 1216136 3796 134348 156271m 64 KB - 27847 0 24363 27847L 16 MB - 0 0 0 0S 16 GB - 0 0 0 0
work pers clnt otherpin 439364 0 3656 81136in use 601823 0 1059865
PageSize PoolSize inuse pgsp pin virtuals 4 KB - 1216136 3796 134348 156271m 64 KB - 27847 0 24363 27847L 16 MB - 0 0 0 0S 16 GB - 0 0 0 0
svmon -O summary=basic,unit=auto
One of the key things to note in this output is that "free" memory is only 49.6M yet "available" memory is 3.06G. This is because, in normal operation, AIX will attempt to use all free memory as a filesystem cache. As long as you don't see much use of paging space then use the "available" figure when working out how much memory you have to spare for other things (like Oracle Database memory tunables).
Unit: auto-------------------------------------------------------------------------------------- size inuse free pin virtual available mmodememory 32.0G 32.0G 49.6M 6.04G 28.5G 3.06G Dedpg space 25.6G 2.26G
work pers clnt otherpin 5.09G 0K 14.3M 962.50Min use 27.6G 0K 4.31G
work pers clnt otherpin 5.09G 0K 14.3M 962.50Min use 27.6G 0K 4.31G
vmstat
vmstat 5 5
vmstat -a
vmstat -Itw 5 5
5 iterations, 5 seconds apart
Show inactive and active memory (instead of buff and cache)
(AIX) I/O oriented view ,with timestamp, wide mode
Example output from vmstat -Itw 5 5System configuration: lcpu=16 mem=32768MB ent=2.00
kthr memory page faults cpu time----------- --------------------- ------------------------------------ ------------------- ----------------------- -------- r b p avm fre fi fo pi po fr sr in sy cs us sy id wa pc ec hr mi se 27 13 0 8138927 5875 69120 10313 0 0 78175 155309 15391 56136 118802 45 47 3 5 3.90 195.0 13:12:35 32 11 0 8128587 5929 62101 5547 0 0 63686 159470 14366 184458 105148 47 46 3 4 3.90 194.8 13:12:40 30 7 0 8110765 5545 48682 2918 0 0 45613 105090 13471 330653 93227 54 36 5 5 3.88 193.9 13:12:45 18 7 0 8107437 6394 52499 3051 0 0 52707 109837 14381 391281 99667 55 35 5 5 3.93 196.4 13:12:50 43 14 0 8106457 5310 92296 2260 0 0 92307 207717 12866 367300 91384 48 42 4 6 3.92 196.1 13:12:55
kthr memory page faults cpu time----------- --------------------- ------------------------------------ ------------------- ----------------------- -------- r b p avm fre fi fo pi po fr sr in sy cs us sy id wa pc ec hr mi se 27 13 0 8138927 5875 69120 10313 0 0 78175 155309 15391 56136 118802 45 47 3 5 3.90 195.0 13:12:35 32 11 0 8128587 5929 62101 5547 0 0 63686 159470 14366 184458 105148 47 46 3 4 3.90 194.8 13:12:40 30 7 0 8110765 5545 48682 2918 0 0 45613 105090 13471 330653 93227 54 36 5 5 3.88 193.9 13:12:45 18 7 0 8107437 6394 52499 3051 0 0 52707 109837 14381 391281 99667 55 35 5 5 3.93 196.4 13:12:50 43 14 0 8106457 5310 92296 2260 0 0 92307 207717 12866 367300 91384 48 42 4 6 3.92 196.1 13:12:55
System Configuration
Note: Entitled capacity relates to AIX LPAR functionality
- lcpu - logical processors
- mem - amount of memory
- ent - entitled capacity
Note: Entitled capacity relates to AIX LPAR functionality
kthrKernel Thread states
- r - average runnable threads over the sampling interval
- b - average kernel threads placed in VMM wait queue (awaiting resourcem awaiting I/O) over the sampling interval
- p - average threads waiting for I/O messages from raw devices
SMT
In our example (on AIX) we can see (using smtctl) that 16 lcpu equates to 4 physical cpu with 4 SMT threads each
memory
- avm - active virtual pages shown as 4K chunks. Divide by 256 to convert to MB.
- fre - size of the free list.
If we divide mem by avm (in MB) we can see that, on this system, virtual memory accounts for over 96% of total memory.
The free list often remains small because a large proportion of real memory will be used as a filesystem cache.
page
- fi - file page-ins per second
- fo - file page-outs per second
- pi - number of pages paged in from paging space over the sampling interval
- po - number of pages paged out to paging space over the sampling interval
- fr - pages freed (page replacement)
- sr - pages scanned by page-replacement algorithm
faults
- in - device interrupts
- sy - system calls
- cs - kernel thread context switches
CPU
- us - % user time
- sy - system time
- id - idle time
- wa - wait time (idle time during which the system had outstanding disk/NFS I/O requests)
- pc - processors consumed
- ec - entitled capacity
If the current processor consumption exceeds the entitled capacity, the percentage becomes relative to the physical processor consumed (pc)
More information...
cat /proc/meminfo
dmidecode --type 17
lshw -short -C memory
Pagesize...
getconf PAGESIZE
Memory Nodes/Zones/Fragmentation...
cat /proc/buddyinfo
Information about storage used for swap...
cat /proc/swaps
cat /etc/fstab
Processes by Memory Usage
Processes by Memory Usage
dstat -d --top-mem
Processes by % Memory Usage...
for file in /proc/*/status
do
awk '/VmSize|Name|Uid/{printf $2 " " $3}END{ print ""}' $file
done | grep 101 | awk '{sum+=$3;} END{print sum;}'
For a breakdown of memory usage for a specifc process (e.g. 222)...
pmap 222
For a breakdown of shared memory usage...
ipcs -b
Processes by % Memory Usage...
ps -o pid,user,%mem,command ax | sort -b -k3 -r
ps -eo pid,cmd,%mem,%cpu --sort=-%mem
ps -eo pid,euser,cmd,vsz --sort=-vsz
ps -eo pid,euser,comm,vsz --sort=-vsz | grep grid | awk '{sum+=$4;} END{print sum;}'
VSZ = Virtual Memory Size - indicates the maximum amount of memory a process would use if it loaded all of its functions and libraries into physical memory. Linux uses "demand" paging which means pages are only loaded into memory when the application uses them. i.e. VSZ does not show how much memory a process is actually using.
RSS = Resident Set Size -indicates used memory. But shared libraries are counted for each process.
RSS = Resident Set Size -indicates used memory. But shared libraries are counted for each process.
Using top...
top
See the MEM% columnShift+m - sort by memory usage.m - toggle memory displayc - toggle full command
Using htop...
htop
See the MEM% columnF6 then select %MEM using cursor keys to sort processes by memory usage
htop
Top 15 Memory Hogs
svmon -Pt15 | perl -e 'while(<>){print if($.==2||$&&&!$s++);$.=0 if(/^-+$/)}'
Sorts on Resident Set Size
ps aux | sort -n -k 6
ps alxww | sort -n -k 11
topas
c - to cycle through CPU detailsd - to cycle through Disk details
Topas Monitor for host:myaixhost1 EVENTS/QUEUES FILE/TTYTue Oct 18 17:27:55 2022 Interval:2 Cswitch 94537 Readch 197.5M Syscall 329.8K Writech 7896.2KCPU User% Kern% Wait% Idle% Physc Entc% Reads 25978 Rawin 0Total 50.3 31.5 10.8 7.4 3.81 190.66 Writes 2468 Ttyout 387 Forks 3 Igets 106Network BPS I-Pkts O-Pkts B-In B-Out Execs 4 Namei 2062Total 975K 363.0 1.00K 39.6K 935K Runqueue 8.00 Dirblk 0 Waitqueue 10.0Disk Busy% BPS TPS B-Read B-Writ MEMORYTotal 32.4 223M 29.0K 210M 12.3M PAGING Real,MB 32768 Faults 36019 % Comp 88FileSystem BPS TPS B-Read B-Writ Steals 54725 % Noncomp 11Total 204M 27.6K 198M 6.87M PgspIn 0 % Client 11 PgspOut 0Name PID CPU% PgSp Owner PageIn 53722 PAGING SPACEoracle 29622312 8.5 20.1M oracle PageOut 3150 Size,MB 26240oracle 55050446 7.9 21.7M oracle Sios 56910 % Used 44oracle 50724986 7.7 10.5M oracle % Free 56oracle 59703408 6.8 19.5M oracle NFS (calls/sec)oracle 36372720 4.7 19.4M oracle SerV2 0 WPAR Activ 0lrud 262152 3.8 640K root CliV2 0 WPAR Total 0oracle 57409682 3.2 25.1M oracle SerV3 0 Press: "h"-helporacle 17367170 2.6 11.6M oracle CliV3 0 "q"-quitoracle 46137462 2.6 18.8M oracle SerV4 0oracle 33095710 2.3 17.3M oracle CliV4 0oracle 63242434 2.3 18.4M oracleoracle 62980230 2.2 18.9M oraclejava 18874548 2.1 329M oracleoracle 39649322 2.1 41.2M oraclevtiol 786456 2.1 1.06M rootoracle 36765752 2.1 18.8M oracleoracle 43122878 2.0 33.2M oracleaioserve 66846838 1.2 448K oracleoracle 62914612 0.8 18.0M oracleoracle 9109524 0.5 22.4M oracle
Bibliography
Bibliography
https://www.golinuxcloud.com/check-memory-usage-per-process-linux/https://www.golinuxcloud.com/how-to-find-memory-leaks/https://www.cyberciti.biz/tips/how-much-ram-does-my-linux-system.html
https://linuxize.com/post/free-command-in-linux/ https://linuxhint.com/check_memory_usage_process_linux/
https://stackoverflow.com/questions/1971422/linux-how-to-put-a-load-on-system-memoryhttps://stackoverflow.com/questions/7880784/what-is-rss-and-vsz-in-linux-memory-management
https://blogs.oracle.com/linux/anticipating-your-memory-needshttps://www.fosslinux.com/43296/linux-ps-command-with-examples.htmhttps://man7.org/linux/man-pages/man1/ps.1.htmlhttps://www.kernel.org/doc/html/latest/filesystems/proc.htmlhttps://linuxconfig.org/ps-output-difference-between-vsz-vs-rss-memory-usagehttps://linuxconfig.org/how-to-monitor-ram-usage-on-linuxhttps://phoenixnap.com/kb/vmstat-commandhttps://www.linuxatemyram.com/
https://unix.stackexchange.com/questions/99334/how-to-fill-90-of-the-free-memoryhttps://unix.stackexchange.com/questions/478443/how-shall-i-understand-the-output-of-freehttps://unix.stackexchange.com/questions/261247/how-can-i-get-the-amount-of-available-memory-portably-across-distributionshttps://unix.stackexchange.com/questions/586249/swap-grows-slowly-with-80-available-memory
https://www.ibm.com/support/pages/memory-analysis-aixhttps://www.ibm.com/docs/en/aix/7.2?topic=usage-memory-determination-ps-commandhttps://developer.ibm.com/articles/using-svmon-to-display-available-memory-on-aix/
https://tecadmin.net/add-swap-partition-on-ec2-linux-instance/
TODO:smemslabtophttps://unix.stackexchange.com/questions/361408/calculate-lpar-cpu-utilization-aix
https://support.oracle.comVirtual Memory Paging Reported Incorrectly on 11.2.0.3 (Doc ID 1515849.1)
AIX Memory Leakshttps://www.ibm.com/support/pages/memory-leak-diagnosis-aix
https://linuxize.com/post/free-command-in-linux/ https://linuxhint.com/check_memory_usage_process_linux/
https://stackoverflow.com/questions/1971422/linux-how-to-put-a-load-on-system-memoryhttps://stackoverflow.com/questions/7880784/what-is-rss-and-vsz-in-linux-memory-management
https://blogs.oracle.com/linux/anticipating-your-memory-needshttps://www.fosslinux.com/43296/linux-ps-command-with-examples.htmhttps://man7.org/linux/man-pages/man1/ps.1.htmlhttps://www.kernel.org/doc/html/latest/filesystems/proc.htmlhttps://linuxconfig.org/ps-output-difference-between-vsz-vs-rss-memory-usagehttps://linuxconfig.org/how-to-monitor-ram-usage-on-linuxhttps://phoenixnap.com/kb/vmstat-commandhttps://www.linuxatemyram.com/
https://unix.stackexchange.com/questions/99334/how-to-fill-90-of-the-free-memoryhttps://unix.stackexchange.com/questions/478443/how-shall-i-understand-the-output-of-freehttps://unix.stackexchange.com/questions/261247/how-can-i-get-the-amount-of-available-memory-portably-across-distributionshttps://unix.stackexchange.com/questions/586249/swap-grows-slowly-with-80-available-memory
https://www.ibm.com/support/pages/memory-analysis-aixhttps://www.ibm.com/docs/en/aix/7.2?topic=usage-memory-determination-ps-commandhttps://developer.ibm.com/articles/using-svmon-to-display-available-memory-on-aix/
https://tecadmin.net/add-swap-partition-on-ec2-linux-instance/
TODO:smemslabtophttps://unix.stackexchange.com/questions/361408/calculate-lpar-cpu-utilization-aix
https://support.oracle.comVirtual Memory Paging Reported Incorrectly on 11.2.0.3 (Doc ID 1515849.1)
AIX Memory Leakshttps://www.ibm.com/support/pages/memory-leak-diagnosis-aix
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