Adds documentation for new tiered spillover cache policy setting (#9374)

* add new TSC policy setting

Signed-off-by: Peter Alfonsi <petealft@amazon.com>

* Update _search-plugins/caching/tiered-cache.md

Co-authored-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Signed-off-by: Peter Alfonsi <peter.alfonsi@gmail.com>

* Update _search-plugins/caching/tiered-cache.md

Co-authored-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Signed-off-by: Peter Alfonsi <peter.alfonsi@gmail.com>

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Signed-off-by: Peter Alfonsi <petealft@amazon.com>
Signed-off-by: Peter Alfonsi <peter.alfonsi@gmail.com>
Co-authored-by: Peter Alfonsi <petealft@amazon.com>
Co-authored-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>

Author: 3 people

_search-plugins/caching/tiered-cache.md

@@ -74,7 +74,8 @@ The following table lists additional settings for the `tiered_spillover` store s
 
 Setting | Data type | Default | Description
 :--- | :--- | :--- | :---
-`indices.requests.cache.tiered_spillover.disk.store.policies.took_time.threshold` | Time unit | `10ms` | A policy used to determine whether to cache a query into a disk cache based on its took time. This is a dynamic setting. Optional.
+`indices.requests.cache.tiered_spillover.policies.took_time.threshold` | Time unit | `0ms` | A policy used to determine whether to cache a query into the cache based on its query phase execution time. This is a dynamic setting. Optional.
+`indices.requests.cache.tiered_spillover.disk.store.policies.took_time.threshold` | Time unit | `10ms` | A policy used to determine whether to cache a query into the disk tier of the cache based on its query phase execution time. This is a dynamic setting. Optional.
 `indices.requests.cache.tiered_spillover.disk.store.enabled` | Boolean | `True` | Enables or disables the disk cache dynamically within a tiered spillover cache. Note: After disabling a disk cache, entries are not removed automatically and requires the cache to be manually cleared. Optional.
 `indices.requests.cache.tiered_spillover.onheap.store.size` | Percentage | 1% of the heap size | Defines the size of the on-heap cache within tiered cache. Optional.
 `indices.requests.cache.tiered_spillover.disk.store.size` | Long | `1073741824` (1 GB) | Defines the size of the disk cache within tiered cache. Optional.