[matheusmoreira]

> the DB has information on access patterns and table format that the OS is not aware of

Aren't system calls such as madvise supposed to allow user space to let the kernel know precisely that information?

[jandrewrogers]

The madvise() functions and similar are a blunt and imprecise instrument. The kernel is free to ignore them, and frequently does in practice. It also does not prevent the kernel from proactively doing things you don't want it to do with your buffer pool at the worst possible time.

A user space buffer pool gives you precise and deterministic control of many of these behaviors.

[ayende]

That is an interesting statement, when discussing what you want to do

In this case, there is the issue of who is the you on question

For the database in isolation, maybe not ideal

For a system whre db and app run on the same machine? The OS can make sure you are on friendly terms and not fighting

Same for trying to SSH to a bust server and the OS can balance things out

[masklinn]

> precisely

Madvise is discussed in the paper, and it notes specifically that:

* madvise is not precise

* madvise is... an advice, which the system is completely free to disregard

* madvise is error-prone, providing the wrong hint can have dire consequences