The patch titled
Subject: zsmalloc: use all available 24 bits of page_type
has been added to the -mm mm-unstable branch. Its filename is
zsmalloc-use-all-available-24-bits-of-page_type.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zsmalloc-use-all-available-24-bits-of-page_type.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: zsmalloc: use all available 24 bits of page_type
Date: Wed, 21 Aug 2024 18:39:12 +0100
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@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/zram/Kconfig | 1 -
mm/Kconfig | 10 ++--------
mm/zsmalloc.c | 15 ++++-----------
3 files changed, 6 insertions(+), 20 deletions(-)
--- a/drivers/block/zram/Kconfig~zsmalloc-use-all-available-24-bits-of-page_type
+++ a/drivers/block/zram/Kconfig
@@ -2,7 +2,6 @@
config ZRAM
tristate "Compressed RAM block device support"
depends on BLOCK && SYSFS && MMU
- depends on HAVE_ZSMALLOC
select ZSMALLOC
help
Creates virtual block devices called /dev/zramX (X = 0, 1, ...).
--- a/mm/Kconfig~zsmalloc-use-all-available-24-bits-of-page_type
+++ a/mm/Kconfig
@@ -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
--- a/mm/zsmalloc.c~zsmalloc-use-all-available-24-bits-of-page_type
+++ a/mm/zsmalloc.c
@@ -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_pag
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
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);
}
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
fs-remove-calls-to-set-and-clear-the-folio-error-flag.patch
mm-remove-pg_error.patch
mm-return-the-folio-from-swapin_readahead.patch
printf-remove-%pgt-support.patch
mm-introduce-page_mapcount_is_type.patch
mm-support-only-one-page_type-per-page.patch
zsmalloc-use-all-available-24-bits-of-page_type.patch
