Helm: persistent cache item_size_max: 5242880 cannot be larger than ext_wbuf_size: 4194304

[rknightion]

Describe the bug
In the latest helm chart that adds persistent memcached, the default chart values lead to a failure of memcached to start with:
persistent cache item_size_max: 5242880 cannot be larger than ext_wbuf_size: 4194304
This is on both the chunks and results cache

This will be because the item_size_max is set to 5mb.

Additionally, I can see the template does the following:
--extended=modern,track_sizes{{ if .persistence.enabled }},ext_path={{ .persistence.mountPath }}/file:{{ .persistence.storageSize }}{{ end }}{{ with .extraExtendedOptions }},{{ . }}{{ end }}
However the docs on this at https://github.com/memcached/memcached/wiki/ConfiguringLokiExtstore indicate a few more settings need changing or optimising such as:

• ext_wbuf_size (the cause of this issue I think)
• ext_threads
• ext_max_sleep
• slab_automove_freeratio

Simply enabling ext cache without doing any of the other performance tweaks I worry could lead users to a subpar experience?
This should at least be documented somewhere if the feat isn't 'complete'?

To Reproduce
Steps to reproduce the behavior:
Set chunksCache.persistence.enabled to true

Expected behavior
The chunks cache and results memcached starts up with persistence enabled

[AndreZiviani]

In #13619 that adds persistent memcached, the default chart values lead to a failure of memcached to start

my bad, implementing a fix for this now

However the docs on this at https://github.com/memcached/memcached/wiki/ConfiguringLokiExtstore indicate a few more settings need changing or optimising

this doc was made before Loki version 3.0, I have based the implementation on this blog post which does not set those values (at least it was not mentioned), but you can always add them yourself via extraExtendedOptions

Simply enabling ext cache without doing any of the other performance tweaks I worry could lead users to a subpar experience?

I don't think so but like I said you can always add them yourself