[pbs-devel] [PATCH proxmox-backup 4/4] docs: add description for gc-cache-capacity tuning parameter

[Lukas Wagner]

On  2025-04-03 14:27, Christian Ebner wrote:
> Adds a bullet point to the listed datastore tuning parameters,
> describing its functionality, implications and typical values.
> 
> Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
> ---
>  docs/storage.rst | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/docs/storage.rst b/docs/storage.rst
> index 490302955..cab65ef79 100644
> --- a/docs/storage.rst
> +++ b/docs/storage.rst
> @@ -435,9 +435,17 @@ There are some tuning related options for the datastore that are more advanced:
>  
>    This can be set with:
>  
> -.. code-block:: console
> +  .. code-block:: console
> +
> +    # proxmox-backup-manager datastore update <storename> --tuning 'sync-level=filesystem'
>  
> -  # proxmox-backup-manager datastore update <storename> --tuning 'sync-level=filesystem'
> +* ``gc-cache-capacity``: Datastore GC least recently used cache capacity:
> +  Allows to control the cache capacity used to keep track of chunks for which
> +  the access time has already been updated during phase 1 of garbage collection.
> +  This avoids multiple updates and increases GC runtime performance. The
> +  capacity is set as the given value multiplied by 1024. Higher values can
> +  reduce GC runtime at the cost of increase memory usage, setting the value to 0
> +  disables caching.

I think we could completely omit the "the capacity is set as the given value multiplied by 1024" sentence here
and consider the fact that the LRU cache size is value * 1024 an implementation detail.
For the user, the exact number of cached digests in the backend is probably not really that important, right?
In reality, they just want some knob that they can adjust in a range from 0 (no caching) to some maximum.

Same of course applies also for the GUI patch and the log message.

What do you think?

-- 
- Lukas