Différences

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

--- tech:memoire_linux [2026/08/01 23:15] – Jean-Baptiste
+++ tech:memoire_linux [2026/09/18 10:19] (Version actuelle) – Jean-Baptiste
@@ Ligne 6: / Ligne 6: @@
 Voir :
 * [[Supervision - sonde Nagios - Memoire Linux]]
+* psacct [[Suivre la conso CPU par utilisateurs]]
 * https://linuxblog.io/free-vs-available-memory-in-linux/
 * https://en.pingcap.com/blog/linux-kernel-vs-memory-fragmentation-2/
@@ Ligne 23: / Ligne 24: @@
 Linux Memory Management :
+* https://fr.wikipedia.org/wiki/Gestionnaire_de_m%C3%A9moire_virtuelle
 * https://lambdafunc.medium.com/linux-memory-management-2c13b5e386f1
 * https://zedas.fr/posts/linux-explained-7-memory-management/
@@ Ligne 30: / Ligne 32: @@
 * https://www.youtube.com/watch?v=Gpm2-ktMLWs
 * https://www.youtube.com/watch?v=A9WLYbE0p-I
+* https://docs.kernel.org/mm/page_tables.html
+Exemples :
+* http://shtroumbiniouf.free.fr/CoursInfo/Systeme2/Cours/GestionMemoire/PageFault/PageFault.html#DebutPage
@@ Ligne 174: / Ligne 178: @@
             - memCached // free = total - used
 ~~~
 ## Exemple
+Voir psacct [[Suivre la conso CPU par utilisateurs]]
 ~~~bash
 free -mt
+ps aux --sort=-%mem | head -n 11
 vmstat -SM 45 10
 vmstat -SM -a 45 10
@@ Ligne 188: / Ligne 196: @@
 ps -eo comm,pcpu,pmem,rss --sort rss | tail -n 30 | tac
 ~~~
 ~~~bash
@@ Ligne 260: / Ligne 270: @@
+-----------------
+* https://www.postgresql.org/docs/current/kernel-resources.html
+Overcommit Memory
+Overcommit Accounting
+Voir :
+* https://clickhouse.com/blog/strict-memory-overcommit-for-postgres
+vm.overcommit_memory=0
+Default
+Heuristic overcommit handling
+vm.overcommit_memory=1
+Always overcommit. Appropriate for some scientific applications. Classic example is code using sparse arrays and just relying on the virtual memory consisting almost entirely of zero pages.
+vm.overcommit_memory=2
+Strict
+setting vm.overcommit_memory=2
+DOES allow overcommit. If you set overcommit_ratio to (say) 200, then memory can be committed to the extent of swap +(RAM * 200/100).
+The current overcommit limit and amount committed are viewable in /proc/meminfo as CommitLimit and Committed_AS
+A la place de overcommit_ratio
+Il est possible d'utiliser vm.overcommit_kbytes
+OOM
+~~~bash
+echo -1000 > /proc/self/oom_score_adj
+cat /proc/<pid>/oom_score
+echo -1000 > /proc/<pid>/oom_score_adj # protect from OOM kill
+~~~
+Or in a specific cgroup, set oom_kill_disable to 1.
+~~~bash
+echo 1000 > /proc/<pid>/oom_score_adj # mark as first target
+~~~
+For systemd services, use `OOMScoreAdjust=-1000` in the unit file to protect critical processes.
+`cgroup_enable=memory swapaccount=1`
+~~~
+$ echo $(($(cat /sys/fs/cgroup/memory/memory.max_usage_in_bytes) / 2**20)) MB
+MB
+$ cat /sys/fs/cgroup/memory/memory.stat
+~~~
+----
+OOM is not invoked when memory.high is reached.
+However, if cgroup memory.max is reached then OOM is invoked.
+TLB hit TLB miss
+~~~bash
+sudo perf stat -e dTLB-loads,dTLB-load-misses,iTLB-loads,iTLB-load-misses -a sleep 60
+perf list | grep -i tlb
+~~~
+Slub
+~~~bash
+slabtop --sort=1
+~~~
+~~~bash
+slabinfo -v
+~~~
+access.redhat.com/
+page_owner=on
+## Premature swapping while there is still plenty of pagecache to be reclaimed
+Cgroup v1
+  * https://access.redhat.com/solutions/6785021
+  * https://fatdba.com/2025/12/12/when-linux-swaps-away-my-sleep-mysql-rhel8-and-the-curious-case-of-high-swap-usage/
+  * https://docs.couchbase.com/server/current/install/install-swap-space.html
+  * https://support.axway.com/kb/192440/language/en
+  * https://communities.sas.com/t5/Administration-and-Deployment/Red-Hat-RHEL-8-Release-Swappiness-Algorithm-Setting-Requires/td-p/921008
+  * https://docs.acceldata.io/odp/documentation/troubleshooting-premature-swapping
+  * [Change in swap behavior between RHEL 7 and RHEL 8 kernels](https://access.redhat.com/solutions/7042476)