memadvise is a Rust crate that can provide the operating system with hints about memory access patterns. For example, if the user calls memadvise::advise() with Advice::Sequential, the kernel may start bringing memory pages into RAM (if they were on disk) starting at the beginning of the block of memory passed.
```rust extern crate memadvise; extern crate page_size;
fn main() { // Allocate block of memory in a system specific manner.
// Get portion of memory block (must be aligned to system page size).
let address: *mut () = ...
let length = 320000;
// Tell the OS to start loading this portion into RAM starting at the beginning.
memadvise::advise(address, length, Advice::Sequential).unwrap();
// Do something with this portion of memory
// Tell the OS we do not need this portion right now.
// That way, the OS can safely swap it out to disk.
memadvise::advise(address, length, Advice::DontNeed).unwrap();
// Do some other stuff.
// Be sure to free block of memory (system specific) at the end.
}
```
memadvise features five different 'hints' used to tell the system how a program will use a certain range of memory.
Normal - no special usage
Random - will use range but in no particular order; OS should not read ahead much
WillNeed - will use range; OS should read ahead more than Random
Sequential - will use range in order; OS should read ahead more than WillNeed
DontNeed - will not use range right now; OS can swap it to disk
memadvise should Work on Windows and any POSIX compatible system (Linux, Mac OSX, etc.).
memadvise is continuously tested on:
* x86_64-unknown-linux-gnu (Linux)
* i686-unknown-linux-gnu
* x86_64-unknown-linux-musl (Linux w/ MUSL)
* i686-unknown-linux-musl
* x86_64-apple-darwin (Mac OSX)
* i686-apple-darwin
* x86_64-pc-windows-msvc (Windows)
* i686-pc-windows-msvc
* x86_64-pc-windows-gnu
* i686-pc-windows-gnu
memadvise is continuously cross-compiled for:
* arm-unknown-linux-gnueabihf
* aarch64-unknown-linux-gnu
* mips-unknown-linux-gnu
* aarch64-unknown-linux-musl
* i686-linux-android
* x86_64-linux-android
* arm-linux-androideabi
* aarch64-linux-android
* i386-apple-ios
* x86_64-apple-ios
* i686-unknown-freebsd
* x86_64-unknown-freebsd
* x86_64-unknown-netbsd
* asmjs-unknown-emscripten