mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 19:00:25 +00:00
![Mike Rapoport (IBM)](/assets/img/avatar_default.png)
It is enough to use a file name to cross-reference another rst document. Jon says: The right things will happen in the HTML output, readers of the plain-text will know immediately where to go, and we don't have to add the label clutter. Drop reference markup and unnecessary labels and use plain file names. Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org> Link: https://lore.kernel.org/r/20230201094156.991542-3-rppt@kernel.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
28 lines
1.2 KiB
ReStructuredText
28 lines
1.2 KiB
ReStructuredText
======
|
|
z3fold
|
|
======
|
|
|
|
z3fold is a special purpose allocator for storing compressed pages.
|
|
It is designed to store up to three compressed pages per physical page.
|
|
It is a zbud derivative which allows for higher compression
|
|
ratio keeping the simplicity and determinism of its predecessor.
|
|
|
|
The main differences between z3fold and zbud are:
|
|
|
|
* unlike zbud, z3fold allows for up to PAGE_SIZE allocations
|
|
* z3fold can hold up to 3 compressed pages in its page
|
|
* z3fold doesn't export any API itself and is thus intended to be used
|
|
via the zpool API.
|
|
|
|
To keep the determinism and simplicity, z3fold, just like zbud, always
|
|
stores an integral number of compressed pages per page, but it can store
|
|
up to 3 pages unlike zbud which can store at most 2. Therefore the
|
|
compression ratio goes to around 2.7x while zbud's one is around 1.7x.
|
|
|
|
Unlike zbud (but like zsmalloc for that matter) z3fold_alloc() does not
|
|
return a dereferenceable pointer. Instead, it returns an unsigned long
|
|
handle which encodes actual location of the allocated object.
|
|
|
|
Keeping effective compression ratio close to zsmalloc's, z3fold doesn't
|
|
depend on MMU enabled and provides more predictable reclaim behavior
|
|
which makes it a better fit for small and response-critical systems.
|