kevin/linux
1
Fork 0
Code

zsmalloc: use all available 24 bits of page_type

Browse Source 
Now that we have an extra 8 bits, we don't need to limit ourselves to
supporting a 64KiB page size.  I'm sure both Hexagon users are grateful,
but it does reduce complexity a little.  We can also remove
reset_first_obj_offset() as calling __ClearPageZsmalloc() will now reset
all 32 bits of page_type.

Link: https://lkml.kernel.org/r/20240821173914.2270383-5-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2024-08-21 18:39:12 +01:00 committed by Andrew Morton
parent 4ffca5a966
commit 04cb7502a5
3 changed files with 6 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
drivers/block/zram/Kconfig
View File

@ -2,7 +2,6 @@
config ZRAM
tristate "Compressed RAM block device support"
depends on BLOCK && SYSFS && MMU
depends on HAVE_ZSMALLOC
depends on CRYPTO_LZO || CRYPTO_ZSTD || CRYPTO_LZ4 || CRYPTO_LZ4HC || CRYPTO_842
select ZSMALLOC
help

10
mm/Kconfig
View File

@ -128,7 +128,7 @@ config ZSWAP_COMPRESSOR_DEFAULT
choice
prompt "Default allocator"
depends on ZSWAP
default ZSWAP_ZPOOL_DEFAULT_ZSMALLOC if HAVE_ZSMALLOC
default ZSWAP_ZPOOL_DEFAULT_ZSMALLOC if MMU
default ZSWAP_ZPOOL_DEFAULT_ZBUD
help
Selects the default allocator for the compressed cache for
@ -154,7 +154,6 @@ config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
bool "zsmalloc"
depends on HAVE_ZSMALLOC
select ZSMALLOC
help
Use the zsmalloc allocator as the default allocator.
@ -187,15 +186,10 @@ config Z3FOLD
page. It is a ZBUD derivative so the simplicity and determinism are
still there.
config HAVE_ZSMALLOC
def_bool y
depends on MMU
depends on PAGE_SIZE_LESS_THAN_256KB # we want <= 64 KiB
config ZSMALLOC
tristate
prompt "N:1 compression allocator (zsmalloc)" if ZSWAP
depends on HAVE_ZSMALLOC
depends on MMU
help
zsmalloc is a slab-based memory allocator designed to store
pages of various compression levels efficiently. It achieves

15
mm/zsmalloc.c
View File

@ -20,7 +20,7 @@
* page->index: links together all component pages of a zspage
* For the huge page, this is always 0, so we use this field
* to store handle.
* page->page_type: PG_zsmalloc, lower 16 bit locate the first object
* page->page_type: PGTY_zsmalloc, lower 24 bits locate the first object
* offset in a subpage of a zspage
*
* Usage of struct page flags:
@ -452,13 +452,7 @@ static inline struct page *get_first_page(struct zspage *zspage)
return first_page;
}
#define FIRST_OBJ_PAGE_TYPE_MASK 0xffff
static inline void reset_first_obj_offset(struct page *page)
{
VM_WARN_ON_ONCE(!PageZsmalloc(page));
page->page_type |= FIRST_OBJ_PAGE_TYPE_MASK;
}
#define FIRST_OBJ_PAGE_TYPE_MASK 0xffffff
static inline unsigned int get_first_obj_offset(struct page *page)
{
@ -468,8 +462,8 @@ static inline unsigned int get_first_obj_offset(struct page *page)
static inline void set_first_obj_offset(struct page *page, unsigned int offset)
{
/* With 16 bit available, we can support offsets into 64 KiB pages. */
BUILD_BUG_ON(PAGE_SIZE > SZ_64K);
/* With 24 bits available, we can support offsets into 16 MiB pages. */
BUILD_BUG_ON(PAGE_SIZE > SZ_16M);
VM_WARN_ON_ONCE(!PageZsmalloc(page));
VM_WARN_ON_ONCE(offset & ~FIRST_OBJ_PAGE_TYPE_MASK);
page->page_type &= ~FIRST_OBJ_PAGE_TYPE_MASK;
@ -808,7 +802,6 @@ static void reset_page(struct page *page)
ClearPagePrivate(page);
set_page_private(page, 0);
page->index = 0;
reset_first_obj_offset(page);
__ClearPageZsmalloc(page);
}