I learnt that when we manage a data structure such as a tree or other graph its nodes are stored in the computer in something called a block and nodes of the graph can make up the block and it is the block that is transferred between secondary and primary memory when a data structure gets moved between primary and secondary memory. So I think it’s pretty clear what a block is, it can consist of different sizes depending on architecture but is often 4K. Now I want to know how a block relates to memory pages. Do pages consist of blocks or what is the relation of blocks to pages? Can we define what a page is in memory in terms of a block?
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You typically try to define a block so it’s either the same size as a memory page, or its size is evenly divisible by the size of a memory page, so an integral number of blocks will fit in a page.
As you mentioned, 4K tends to work well — typical memory page sizes are 4K and 8K. Most also support at least one larger page size (e.g., 1 megabyte) but you can typically more or less ignore them; they’re used primarily for mapping single, large chunks of contiguous memory (e.g., the part of graphics memory that’s directly visible to the CPU).