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Ci-dessous, les différences entre deux révisions de la page.

--- tech:memoire_linux [2025/10/23 18:24] – Jean-Baptiste
+++ tech:memoire_linux [2026/07/20 09:54] (Version actuelle) – Jean-Baptiste
@@ Ligne 1: / Ligne 1: @@
+<!DOCTYPE markdown>
+{{tag>Mem SNMP}}
+# Mémoire Linux
+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
+* lsmem / chmem
+* https://linuxfr.org/news/sortie-du-noyau-linux-6-17 damon_stat
+* slabtop
+* memstrack
+* smem - memory reporting tool
+* smemcap - data collection tool for memory reporting
+* smemstat - memory usage monitoring tool
+## Fuite mémoire
+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://www.atoptool.nl/download/case_leakage.pdf)
+* https://github.com/iovisor/bcc/blob/master/README.md tools/memleak
+## Config
+### Kernel Linux param
+#### NUMA (Non-Uniform Memory Access)
+Voir :
+ * [What is NUMA ?](https://www.kernel.org/doc/html/v4.19/vm/numa.html)
+ * [La mémoire : numactl, lstopo, perf, etc.](https://www.it-connect.fr/chapitres/la-memoire-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
+~~~ini
+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
+#### NUMA (Non-Uniform Memory Access) - Useful Commands
+To identify NUMA nodes, socket memory and CPU core allocation
+~~~bash
+numactl -H
+~~~
+To identify the NUMA node local to an adapter
+~~~bash
+cat /sys/class/net/<interface>/device/numa_node
+~~~
+To identify memory allocation and use on a particular NUMA node:
+~~~bash
+cat /sys/devices/system/node/node<N>/numastat
+~~~
+To identify NUMA node mapping to cores, use one of the following
+~~~bash
+numactl --hardware
+cat /sys/devices/system/node/node<N>/cpulist
+~~~
+Driver Loading - NUMA Node
+~~~bash
+numactl --cpunodebind=1 onload_tool reload
+~~~
+### Memory usage per user
+~~~bash
+smem -u
+~~~
+### Transparent HugePages (THP)
+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
+#### Désactiver **Transparent HugePages (THP)**
+~~~bash
+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
+~~~ini
+transparent_hugepage=never
+~~~
+## Notes Free / Aviable
+~~~
+$ ./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
+~~~
+## Exemple
+~~~bash
+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
+~~~
+~~~bash
+read CommitLimit Committed_AS <<< $(egrep "CommitLimit|Committed_AS" /proc/meminfo | awk '{print $2}')
+echo $(( Committed_AS * 100 / CommitLimit))
+~~~
+~~~bash
+memused=$(free  | grep "buffers/cache" | awk '{print $3}')
+memtotal=$(free | grep ^Mem | awk '{print $2}')
+echo $(( memused * 100 / memtotal))
+~~~
+~~~bash
+memFree=$(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]
+~~~
+~~~bash
+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
+~~~
+~~~bash
+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
+~~~
+## Fonctionnement
+Voir :
+OOM Killer et Overcommit Memory
+http://www.blog.florian-bogey.fr/empecher-les-depassements-de-memoire-sur-un-serveur-linux.html
+## Autres
+Clearing KernelCare Cache
+Source : https://www.linuxjournal.com/content/how-install-and-uninstall-kernelcare
+~~~bash
+rm -rf /var/cache/kcare/patches
+echo 1 > /proc/sys/vm/compact_memory
+echo 3 > /proc/sys/vm/drop_caches
+kcarectl –update
+~~~