mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2026-04-14 09:57:39 +02:00
6df8bae8e8
The zbud compressed pages allocator is rarely used, most users use zsmalloc. zbud consumes much more memory (only stores 1 or 2 compressed pages per physical page). The only advantage of zbud is a marginal performance improvement that by no means justify the memory overhead. Historically, zsmalloc had significantly worse latency than zbud and z3fold but offered better memory savings. This is no longer the case as shown by a simple recent analysis [1]. In a kernel build test on tmpfs in a limited cgroup, zbud 2-3% less time than zsmalloc, but at the cost of using ~32% more memory (1.5G vs 1.13G). The tradeoff does not make sense for zbud in any practical scenario. The only alleged advantage of zbud is not having the dependency on CONFIG_MMU, but CONFIG_SWAP already depends on CONFIG_MMU anyway, and zbud is only used by zswap. Remove zbud after z3fold's removal, leaving zsmalloc as the one and only zpool allocator. Leave the removal of the zpool API (and its associated config options) to a followup cleanup after no more allocators show up. Deprecating zbud for a few cycles before removing it was initially proposed [2], like z3fold was marked as deprecated for 2 cycles [3]. However, Johannes rightfully pointed out that the 2 cycles is too short for most downstream consumers, and z3fold was deprecated first only as a courtesy anyway. [1]https://lore.kernel.org/lkml/CAJD7tkbRF6od-2x_L8-A1QL3=2Ww13sCj4S3i4bNndqF+3+_Vg@mail.gmail.com/ [2]https://lore.kernel.org/lkml/Z5gdnSX5Lv-nfjQL@google.com/ [3]https://lore.kernel.org/lkml/20240904233343.933462-1-yosryahmed@google.com/ Link: https://lkml.kernel.org/r/20250129180633.3501650-3-yosry.ahmed@linux.dev Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev> Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Nhat Pham <nphamcs@gmail.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Chengming Zhou <chengming.zhou@linux.dev> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Dan Streetman <ddstreet@ieee.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Huacai Chen <chenhuacai@kernel.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Seth Jennings <sjenning@redhat.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vitaly Wool <vitaly.wool@konsulko.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: WANG Xuerui <kernel@xen0n.name> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
103 lines
2.8 KiB
C
103 lines
2.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
/*
|
|
* zpool memory storage api
|
|
*
|
|
* Copyright (C) 2014 Dan Streetman
|
|
*
|
|
* This is a common frontend for the zswap compressed memory storage
|
|
* implementations.
|
|
*/
|
|
|
|
#ifndef _ZPOOL_H_
|
|
#define _ZPOOL_H_
|
|
|
|
struct zpool;
|
|
|
|
/*
|
|
* Control how a handle is mapped. It will be ignored if the
|
|
* implementation does not support it. Its use is optional.
|
|
* Note that this does not refer to memory protection, it
|
|
* refers to how the memory will be copied in/out if copying
|
|
* is necessary during mapping; read-write is the safest as
|
|
* it copies the existing memory in on map, and copies the
|
|
* changed memory back out on unmap. Write-only does not copy
|
|
* in the memory and should only be used for initialization.
|
|
* If in doubt, use ZPOOL_MM_DEFAULT which is read-write.
|
|
*/
|
|
enum zpool_mapmode {
|
|
ZPOOL_MM_RW, /* normal read-write mapping */
|
|
ZPOOL_MM_RO, /* read-only (no copy-out at unmap time) */
|
|
ZPOOL_MM_WO, /* write-only (no copy-in at map time) */
|
|
|
|
ZPOOL_MM_DEFAULT = ZPOOL_MM_RW
|
|
};
|
|
|
|
bool zpool_has_pool(char *type);
|
|
|
|
struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp);
|
|
|
|
const char *zpool_get_type(struct zpool *pool);
|
|
|
|
void zpool_destroy_pool(struct zpool *pool);
|
|
|
|
bool zpool_malloc_support_movable(struct zpool *pool);
|
|
|
|
int zpool_malloc(struct zpool *pool, size_t size, gfp_t gfp,
|
|
unsigned long *handle);
|
|
|
|
void zpool_free(struct zpool *pool, unsigned long handle);
|
|
|
|
void *zpool_map_handle(struct zpool *pool, unsigned long handle,
|
|
enum zpool_mapmode mm);
|
|
|
|
void zpool_unmap_handle(struct zpool *pool, unsigned long handle);
|
|
|
|
u64 zpool_get_total_pages(struct zpool *pool);
|
|
|
|
|
|
/**
|
|
* struct zpool_driver - driver implementation for zpool
|
|
* @type: name of the driver.
|
|
* @list: entry in the list of zpool drivers.
|
|
* @create: create a new pool.
|
|
* @destroy: destroy a pool.
|
|
* @malloc: allocate mem from a pool.
|
|
* @free: free mem from a pool.
|
|
* @sleep_mapped: whether zpool driver can sleep during map.
|
|
* @map: map a handle.
|
|
* @unmap: unmap a handle.
|
|
* @total_size: get total size of a pool.
|
|
*
|
|
* This is created by a zpool implementation and registered
|
|
* with zpool.
|
|
*/
|
|
struct zpool_driver {
|
|
char *type;
|
|
struct module *owner;
|
|
atomic_t refcount;
|
|
struct list_head list;
|
|
|
|
void *(*create)(const char *name, gfp_t gfp);
|
|
void (*destroy)(void *pool);
|
|
|
|
bool malloc_support_movable;
|
|
int (*malloc)(void *pool, size_t size, gfp_t gfp,
|
|
unsigned long *handle);
|
|
void (*free)(void *pool, unsigned long handle);
|
|
|
|
bool sleep_mapped;
|
|
void *(*map)(void *pool, unsigned long handle,
|
|
enum zpool_mapmode mm);
|
|
void (*unmap)(void *pool, unsigned long handle);
|
|
|
|
u64 (*total_pages)(void *pool);
|
|
};
|
|
|
|
void zpool_register_driver(struct zpool_driver *driver);
|
|
|
|
int zpool_unregister_driver(struct zpool_driver *driver);
|
|
|
|
bool zpool_can_sleep_mapped(struct zpool *pool);
|
|
|
|
#endif
|