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SubjectRe: [RFC PATCH 0/9] mm/zbud: support highmem pages
On Tue, Oct 14, 2014 at 7:59 AM, Heesub Shin <> wrote:
> zbud is a memory allocator for storing compressed data pages. It keeps
> two data objects of arbitrary size on a single page. This simple design
> provides very deterministic behavior on reclamation, which is one of
> reasons why zswap selected zbud as a default allocator over zsmalloc.
> Unlike zsmalloc, however, zbud does not support highmem. This is
> problomatic especially on 32-bit machines having relatively small
> lowmem. Compressing anonymous pages from highmem and storing them into
> lowmem could eat up lowmem spaces.
> This limitation is due to the fact that zbud manages its internal data
> structures on zbud_header which is kept in the head of zbud_page. For
> example, zbud_pages are tracked by several lists and have some status
> information, which are being referenced at any time by the kernel. Thus,
> zbud_pages should be allocated on a memory region directly mapped,
> lowmem.
> After some digging out, I found that internal data structures of zbud
> can be kept in the struct page, the same way as zsmalloc does. So, this
> series moves out all fields in zbud_header to struct page. Though it
> alters quite a lot, it does not add any functional differences except
> highmem support. I am afraid that this kind of modification abusing
> several fields in struct page would be ok.

Seth, have you had a chance to review this yet? I'm going to try to
take a look at it next week if you haven't yet. Letting zbud use
highmem would be a good thing.

> Heesub Shin (9):
> mm/zbud: tidy up a bit
> mm/zbud: remove buddied list from zbud_pool
> mm/zbud: remove lru from zbud_header
> mm/zbud: remove first|last_chunks from zbud_header
> mm/zbud: encode zbud handle using struct page
> mm/zbud: remove list_head for buddied list from zbud_header
> mm/zbud: drop zbud_header
> mm/zbud: allow clients to use highmem pages
> mm/zswap: use highmem pages for compressed pool
> mm/zbud.c | 244 ++++++++++++++++++++++++++++++-------------------------------
> mm/zswap.c | 4 +-
> 2 files changed, 121 insertions(+), 127 deletions(-)
> --
> 1.9.1

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