[PATCH 3/5] mm: Kconfig: simplify zswap configuration

Johannes Weiner
2022-04-27T16:00:14Z

- CONFIG_ZRAM: Zram is a user-facing feature, whereas zsmalloc is
not. Don't make the user chase down a technical dependency like
that, just select it in automatically when zram is requested. The
CONFIG_CRYPTO dependency is redundant due to more specific deps.

- CONFIG_ZPOOL: This is not a user-facing feature. Hide the symbol and
have it selected in as needed.

- CONFIG_ZSWAP: Select CRYPTO instead of depend. Common pattern.

- Make the ZSWAP suboptions and their descriptions (compression,
allocation backend) a bit more straight-forward for the user.

Signed-off-by: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
---
drivers/block/zram/Kconfig | 3 ++-
mm/Kconfig | 55 +++++++++++++++++---------------------
2 files changed, 27 insertions(+), 31 deletions(-)

diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
index 668c6bf2554d..e4163d4b936b 100644
--- a/drivers/block/zram/Kconfig
+++ b/drivers/block/zram/Kconfig
@@ -1,8 +1,9 @@
# SPDX-License-Identifier: GPL-2.0
config ZRAM
tristate "Compressed RAM block device support"
- depends on BLOCK && SYSFS && ZSMALLOC && CRYPTO
+ depends on BLOCK && SYSFS
depends on CRYPTO_LZO || CRYPTO_ZSTD || CRYPTO_LZ4 || CRYPTO_LZ4HC || CRYPTO_842
+ select ZSMALLOC
help
Creates virtual block devices called /dev/zramX (X = 0, 1, ...).
Pages written to these disks are compressed and stored in memory
diff --git a/mm/Kconfig b/mm/Kconfig
index 2c5935a28edf..c87ffd0d98b3 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -9,6 +9,9 @@ menu "Memory Management options"
config ARCH_NO_SWAP
bool

+config ZPOOL
+ bool
+
menuconfig SWAP
bool "Support for paging of anonymous memory (swap)"
depends on MMU && BLOCK && !ARCH_NO_SWAP
@@ -21,8 +24,9 @@ menuconfig SWAP

config ZSWAP
bool "Compressed cache for swap pages (EXPERIMENTAL)"
- depends on SWAP && CRYPTO=y
+ depends on SWAP
select FRONTSWAP
+ select CRYPTO
select ZPOOL
help
A lightweight compressed cache for swap pages. It takes
@@ -38,8 +42,18 @@ config ZSWAP
they have not be fully explored on the large set of potential
configurations and workloads that exist.

+config ZSWAP_DEFAULT_ON
+ bool "Enable the compressed cache for swap pages by default"
+ depends on ZSWAP
+ help
+ If selected, the compressed cache for swap pages will be enabled
+ at boot, otherwise it will be disabled.
+
+ The selection made here can be overridden by using the kernel
+ command line 'zswap.enabled=' option.
+
choice
- prompt "Compressed cache for swap pages default compressor"
+ prompt "Default compressor"
depends on ZSWAP
default ZSWAP_COMPRESSOR_DEFAULT_LZO
help
@@ -105,7 +119,7 @@ config ZSWAP_COMPRESSOR_DEFAULT
default ""

choice
- prompt "Compressed cache for swap pages default allocator"
+ prompt "Default allocator"
depends on ZSWAP
default ZSWAP_ZPOOL_DEFAULT_ZBUD
help
@@ -145,26 +159,9 @@ config ZSWAP_ZPOOL_DEFAULT
default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
default ""

-config ZSWAP_DEFAULT_ON
- bool "Enable the compressed cache for swap pages by default"
- depends on ZSWAP
- help
- If selected, the compressed cache for swap pages will be enabled
- at boot, otherwise it will be disabled.
-
- The selection made here can be overridden by using the kernel
- command line 'zswap.enabled=' option.
-
-config ZPOOL
- tristate "Common API for compressed memory storage"
- depends on ZSWAP
- help
- Compressed memory storage API. This allows using either zbud or
- zsmalloc.
-
config ZBUD
- tristate "Low (Up to 2x) density storage for compressed pages"
- depends on ZPOOL
+ tristate "2:1 compression allocator (zbud)"
+ depends on ZSWAP
help
A special purpose allocator for storing compressed pages.
It is designed to store up to two compressed pages per physical
@@ -173,8 +170,8 @@ config ZBUD
density approach when reclaim will be used.

config Z3FOLD
- tristate "Up to 3x density storage for compressed pages"
- depends on ZPOOL
+ tristate "3:1 compression allocator (z3fold)"
+ depends on ZSWAP
help
A special purpose allocator for storing compressed pages.
It is designed to store up to three compressed pages per physical
@@ -182,15 +179,13 @@ config Z3FOLD
still there.

config ZSMALLOC
- tristate "Memory allocator for compressed pages"
+ tristate
+ prompt "N:1 compression allocator (zsmalloc)" if ZSWAP
depends on MMU
help
zsmalloc is a slab-based memory allocator designed to store
- compressed RAM pages. zsmalloc uses virtual memory mapping
- in order to reduce fragmentation. However, this results in a
- non-standard allocator interface where a handle, not a pointer, is
- returned by an alloc(). This handle must be mapped in order to
- access the allocated space.
+ pages of various compression levels efficiently. It achieves
+ the highest storage density with the least amount of fragmentation.

config ZSMALLOC_STAT
bool "Export zsmalloc statistics"
--
2.35.3