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[CI:DOCS] performance: document sometimes slow native overlayfs

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Signed-off-by: Erik Sjölund <erik.sjolund@gmail.com>
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Erik Sjölund
2023-11-27 17:07:47 +01:00
parent 3a841ce6a9
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docs/tutorials/performance.md
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@ -65,6 +65,24 @@ The following storage drivers are listed from fastest to slowest:
2. fuse-overlayfs
3. vfs
There is one notable exception to this speed ranking.
Creating a container takes significantly longer with _native overlayfs_ than _fuse-overlayfs_
when these conditions are all met:
* rootless Podman is used
* a modified UID/GID mapping is used
* _native overlayfs_ is used
* no container has yet been created with the specified container image and UID/GID mapping
Runtime speed is not affected. Only __podman create__ and the container creation phases of
__podman run__ and __podman build__ are affected.
For more details, see [GitHub comment](https://github.com/containers/podman/issues/16541#issuecomment-1352790422).
Command-line options that modify the UID/GID mapping are for example __--userns__, __--uidmap__ and __--gidmap__.
The command-line option `--userns auto` is particularly affected by this performance penalty,
because different UID/GID mappings could potentially be used on each invocation. For other uses of
__--userns__, __--uidmap__ and __--gidmap__ the performance penalty is a one-time cost
that only occurs the first time the command is run.
Using native overlayfs as an unprivileged user is only available for Podman version >= 3.1 on a Linux kernel version >= 5.12.
To show the current storage driver