Update default object store page size to 4k

[badrishc]

Update default object store page size to 4k. See discussion here: #1097 (comment) and the documentation here: https://microsoft.github.io/garnet/docs/getting-started/memory#log-size-object-store

Default object store page size of 1m is way too large, as memory is reclaimed in chunks of page-worth of objects. This PR will allow the ObjectStoreHeapMemorySize setting to reclaim heap space in reasonable granularity (around 170 objects at a time).

10::50::31 info: Options[0] [Object Store] Using page size of 4k
10::50::31 info: Options[0] [Object Store] Each page can hold ~170 key-value pairs of objects
10::50::31 info: Options[0] [Object Store] Using log memory size of 32m
10::50::31 info: Options[0] [Object Store] This can hold ~1398101 key-value pairs of objects in memory total
10::50::31 info: Options[0] [Object Store] There are 8k log pages in memory

[Copilot]

Pull Request Overview

This PR updates the default object store page size from "1m" to "4k" to allow for more granular memory reclamation.

• Updated the default page size in the server options.
• Updated the default configuration file accordingly.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
libs/server/Servers/GarnetServerOptions.cs	Default object store page size updated from "1m" to "4k".
libs/host/defaults.conf	Default configuration updated to reflect the new page size "4k".