Erik Darling, despite being on Team Profiler, has something important to say:
If you’re the kind of person who cares about various caches on your server, like the buffer pool or the plan cache, then you’d wanna measure something totally different. You’d wanna measure how much free space you have on each page, because having a bunch of empty space on each page means your data will take up more space in memory when you read it in there from disk.
You could do that with the column avg_page_space_used_in_percent.
BUT…
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