This is a freelist allocator with static size classes that works as a
complement to the generic kmalloc(). It's a lot faster than kmalloc()
since allocation just means popping from the freelist.
It's also significantly more compact when there are a lot of objects
smaller than the minimum kmalloc chunk size (32 bytes.)
This patch enables it for the Region and PhysicalPage classes.
In the PhysicalPage (8 bytes) case, it's a huge improvement since we
no longer waste 75% of the storage allocated.
There are also a number of ways this can be improved, so let's keep
working on it going forward.
This was a workaround to be able to build on case-insensitive file
systems where it might get confused about <string.h> vs <String.h>.
Let's just not support building that way, so String.h can have an
objectively nicer name. :^)
We were doing this for the initial kernel-spawned userspace process(es)
to work around instability in the page fault handler. Now that the page
fault handler is more robust, we can stop worrying about this.
Specifically, the page fault handler was previous not able to handle
getting a page fault in anything but the currently executing task's
page directory.
Remove the global hash tables and replace them with InlineLinkedLists.
This significantly reduces the kernel heap pressure from doing many
small mmap()'s.
Region now has is_user_accessible(), which informs the memory manager how
to map these pages. Previously, we were just passing a "bool user_allowed"
to various functions and I'm not at all sure that any of that was correct.
All the Region constructors are now hidden, and you must go through one of
these helpers to construct a region:
- Region::create_user_accessible(...)
- Region::create_kernel_only(...)
That ensures that we don't accidentally create a Region without specifying
user accessibility. :^)
This is obviously more readable. If we ever run into a situation where
ref count churn is actually causing trouble in the future, we can deal with
it then. For now, let's keep it simple. :^)
String&& is just not very practical. Also return const String& when the
returned string is a member variable. The call site is free to make a copy
if he wants, but otherwise we can avoid the retain count churn.
Also run it across the whole tree to get everything using the One True Style.
We don't yet run this in an automated fashion as it's a little slow, but
there is a snippet to do so in makeall.sh.
