[scott_s]

It's commonly done in memory allocators at various levels. You inherently want to manage pages, and you'll carve out the start of the page itself to hold its own data structure.

You can see an example of this technique here: https://github.com/scotts/streamflow/blob/master/streamflow....

This bit of code executes when a call to malloc() could not find any free memory, and it has to request more memory from the operating system. The function supermap() allocates a large chunk of memory from the kernel. We then write the meta-information to keep track of that chunk of memory directly to itself - that "meta-information" is the pageblock_t struct. In malloc(), we then use that chunk of memory to find a sub-chunk inside of it to return to the user.

Note that internal to malloc(), we will maintain lists of these pageblock_t structures, and they will all be page-aligned. So, anytime we want to search for free memory among the managed pages, we're going to access page-aligned structures.