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Update section about swap with cgroups v2 info

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Jerome Petazzoni
2020-11-15 16:44:18 +01:00
parent bdede6de07
commit 32250f8053
1 changed files with 6 additions and 4 deletions
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10
slides/k8s/resource-limits.md
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@@ -56,8 +56,6 @@
- Exceeding the memory limit will cause the container to be killed
---
## Limits vs requests
@@ -122,13 +120,17 @@ Each pod is assigned a QoS class (visible in `status.qosClass`).
- The semantics of memory and swap limits on Linux cgroups are complex
- In particular, it's not possible to disable swap for a cgroup
- With cgroups v1, it's not possible to disable swap for a cgroup
(the closest option is to [reduce "swappiness"](https://unix.stackexchange.com/questions/77939/turning-off-swapping-for-only-one-process-with-cgroups))
- It is possible with cgroups v2 (see the [kernel docs](https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html) and the [fbatx docs](https://facebookmicrosites.github.io/cgroup2/docs/memory-controller.html#using-swap))
- Cgroups v2 aren't widely deployed yet
- The architects of Kubernetes wanted to ensure that Guaranteed pods never swap
- The only solution was to disable swap entirely
- The simplest solution was to disable swap entirely
---