Différences

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

--- tech:notes_swap_memoire [2026/06/07 19:12] – modification externe 127.0.0.1
+++ tech:notes_swap_memoire [2026/07/20 09:51] (Version actuelle) – Jean-Baptiste
@@ Ligne 1: / Ligne 1: @@
 <!DOCTYPE markdown>
-{{tag>Brouillon}}
+{{tag>Brouillon Mémoire SWAP Kernel Linux}}
 # Notes swap mémoire
 Voir :
+* https://wiki.debian.org/Swap
 * https://chrisdown.name/2018/01/02/in-defence-of-swap.html
 * https://kubernetes.io/blog/2025/03/25/swap-linux-improvements/
@@ Ligne 63: / Ligne 64: @@
 ~~~
+ou
+~~~bash
+for file in /proc/*/status ; do awk '/Tgid|VmSwap|Name/{printf $2 " " $3}END{ print ""}' $file; done | grep kB | sort -k 3 -n
+~~~
@@ Ligne 70: / Ligne 76: @@
 dphys-swapfile swapoff
 ~~~
 ## Recommandations SWAP
@@ Ligne 102: / Ligne 109: @@
+## Utilisation de SWAP alors que la RAM n'est que partiellement utilisé
+En anglais sur les forums :
+  * Why is Swap used when there is RAM available?
+  * Swap being used when RAM is almost half free
+  * Why linux has enough memory but swap is used
+  * Why is Linux not using RAM but only Swap ?
+  * System suddenly using all available swap, but plenty of free memory
+  * High swap usage in spite of low RAM usage
+Voir :
+* https://en.wikipedia.org/wiki/Memory_paging
+* https://www.reddit.com/r/linux4noobs/comments/1aep2bc/why_is_swap_used_when_there_is_ram_available/
+Voir aussi :
+* Shared Memory
+* zramctl
+~~~bash
+cat /proc/meminfo
+cat /proc/sys/vm/swappiness
+cat /proc/sys/vm/dirty_ratio
+cat /proc/sys/vm/dirty_background_ratio
+cat /proc/sys/vm/overcommit_ratio
+~~~
+Voir VmSwap ou VmSize
+~~~bash
+ps -eo pmem,pcpu,rss,vsize,args --sort rss
+grep VmSwap /proc/*/status | sort -n -r --key=2.1 | head -5
+grep Vm /proc/3593/status
+~~~
+## Tests SWAP
+Utiliser 2 giga de mémoire
+~~~bash
+stress --vm 1 --vm-bytes 2G --timeout 30
+~~~
+Vérif
+~~~bash
+journalctl -k | grep -i "out of memory"
+~~~
+Autres test
+~~~c
+#include <stdlib.h>
+#include <strings.h>
+#include <unistd.h>
+int main()
+{
+    char *p;
+    size_t s = 100 * 1024 * 1024;
+    for (;;)
+    {
+        p = malloc(s);
+        bzero(p, s);
+        sleep(1);
+    }
+    /* unreached */
+}
+~~~
+Source : https://bbs.archlinux.org/viewtopic.php?id=212750