Voir :

• Supervision - sonde Nagios - Memoire Linux
• https://linuxblog.io/free-vs-available-memory-in-linux/
• https://en.pingcap.com/blog/linux-kernel-vs-memory-fragmentation-2/
• /proc/sys/vm/compact_memory
• procmap
• pmap
• smem
• lsmem / chmem
• https://linuxfr.org/news/sortie-du-noyau-linux-6-17 damon_stat

Voir :

• Valgrind
• https://www.hebergementwebs.com/tutoriels/linux-recherche-de-fuites-de-memoire-dans-les-programmes
• https://qastack.fr/unix/36450/how-can-i-find-a-memory-leak-of-a-running-process
• https://www.linuxtricks.fr/wiki/performance-memoire-avec-free-et-vmstat
• http://www.ordinateur.cc/syst%C3%A8mes/Linux/205699.html
• Atop - Case study with atop: memory leakage
• https://github.com/iovisor/bcc/blob/master/README.md tools/memleak

Voir :

• What is NUMA ?
• La mémoire : numactl, lstopo, perf, etc.
• numatop

Disable NUMA (Pour Oracle DB) /usr/share/doc/kernel-doc-4.18.0/Documentation/x86/x86_64/boot-options.txt

numa=off      Only set up a single NUMA node spanning all memory.

Vérif

numactl command can be used to check the status of NUMA

# numactl -H | grep available
available: 8 nodes (0-7)

# numactl -H | grep available
available: 2 nodes (0-1)

If the number of available nodes is 2 nodes (0-1) or 8 nodes (0-7) then NUMA is enabled

If the number of available nodes is 1 nodes (0) then NUMA is not enabled.

Voir aussi :

• numastat
• numademo

To identify NUMA nodes, socket memory and CPU core allocation

numactl -H

To identify the NUMA node local to an adapter

cat /sys/class/net/<interface>/device/numa_node

To identify memory allocation and use on a particular NUMA node:

cat /sys/devices/system/node/node<N>/numastat

To identify NUMA node mapping to cores, use one of the following

numactl --hardware
cat /sys/devices/system/node/node<N>/cpulist

Driver Loading - NUMA Node

numactl --cpunodebind=1 onload_tool reload

smem -u

Voir

• https://blog.zwindler.fr/2020/02/24/transparent-hugepages-mesurer-limpact-sur-les-performances/
• https://www.postgresql.org/docs/9.4/kernel-resources.html

cat /sys/kernel/mm/transparent_hugepage/enabled

The following is a sample output that shows Transparent HugePages are being used as the [always] flag is enabled.

[always] never

Paramètre Kernel Linux

transparent_hugepage=never

$ ./centreon_plugins.pl --plugin os::linux::snmp::plugin --mode memory --hostname localhost --help
...
    --patch-redhat
            If using Red Hat distribution with net-snmp >= 5.7.2-43 and
            net-snmp < 5.7.2-47. But you should update net-snmp!!!!

            This version: used = memTotalReal - memAvailReal // free =
            memAvailReal

            Others versions: used = memTotalReal - memAvailReal - memBuffer
            - memCached // free = total - used

free -mt
vmstat -SM 45 10
vmstat -SM -a 45 10
ps -C apache2 -o rss --no-headers |tr "\n" "+" | sed -e 's/+$/\n/' |bc
ps -e -o pid,user,%mem,rss,vsize,cmd --sort rss
ps -e -o pid,user,%mem,rss,vsize,cmd --sort vsize
ps -u $USER -o comm,vsz,pcpu | sort -nrk2
ps -eo comm,pcpu,pmem,rss --sort rss | tail -n 30 | tac

read CommitLimit Committed_AS <<< $(egrep "CommitLimit|Committed_AS" /proc/meminfo |awk '{print $2}')
echo $(( Committed_AS * 100 / CommitLimit))

memused=$(free  |grep "buffers/cache" |awk '{print $3}')
memtotal=$(free |grep ^Mem | awk '{print $2}')
echo $(( memused * 100 / memtotal))

memFree=$(free |grep ^-|awk '{print $3}')
memTot=$(free |grep ^Mem |awk '{print $2}')
memUsed=$(echo "scale=2 ; 100 * $memFree / $memTot" |bc)
echo "$memUsed %  Mem used" | grep ^[3-9][0-9]

ps -C apache2 -o rss --no-headers |tr "\n" "+" | sed -e 's/+$/\n/' |bc
read CommitLimit Committed_AS <<< $(egrep "CommitLimit|Committed_AS" /proc/meminfo |awk '{print $2}')
echo $(( Committed_AS * 100 / CommitLimit))
memused=$(free  |grep "buffers/cache" |awk '{print $3}')
memtotal=$(free |grep ^Mem | awk '{print $2}')
echo $(( memused * 100 / memtotal))
ps -e -o pid,user,rss,vsize,cmd --sort rss

smem -u
smem -u -t -k
top -b -n 1 -u apache

Taille totale de la mémoire physique de la RAM (sans la swap)

# head -1 /proc/meminfo
MemTotal:       65391036 kB

# awk '/MemTotal/ { print $2 }' /proc/meminfo
65391036

Voir : OOM Killer et Overcommit Memory http://www.blog.florian-bogey.fr/empecher-les-depassements-de-memoire-sur-un-serveur-linux.html

Clearing KernelCare Cache

Source : https://www.linuxjournal.com/content/how-install-and-uninstall-kernelcare

rm -rf /var/cache/kcare/patches
echo 1 > /proc/sys/vm/compact_memory
echo 3 > /proc/sys/vm/drop_caches
kcarectl –update