1. A method implemented at least in part by a computer that includes first tier memory, second tier memory that is slower than the first tier memory, and third tier memory that is slower than the second tier memory, the method comprising: accessing metadata concerning a plurality of pages of a buffer pool, the buffer pool including one or more pages that are stored in the first tier memory, and one or more pages that are stored in the second tier memory; determining, from the metadata, a first threshold and a second threshold, wherein the first threshold and a second threshold are usable to classify the pages within one of at least three classifications, wherein: (i) a page is classified with a first classification if applying a function to access data represented by the metadata of the page returns a value less than the first threshold; (ii) the page is classified with a second classification if applying the function to access the data represented by the metadata of the page returns a value greater than the first threshold but less than the second threshold; or (iii) the page is classified with a third classification if applying the function to the access data of the metadata of the page returns a value greater than the second threshold; and based on the first and second thresholds: evicting a particular page from the second tier memory to the third tier memory, to free space for one or more other pages in the second tier memory, when the particular page is classified with the first classification; evicting the particular page from the first tier memory to the second tier memory, to free space for one or more other pages in the first tier memory, when the particular page is classified with the second classification; and leaving the particular page in the first tier when the particular page is classified with the third classification.