+config ZSWAP
+ bool "Compressed cache for swap pages (EXPERIMENTAL)"
+ depends on SWAP && CRYPTO=y
+ select FRONTSWAP
+ select ZPOOL
+ help
+ A lightweight compressed cache for swap pages. It takes
+ pages that are in the process of being swapped out and attempts to
+ compress them into a dynamically allocated RAM-based memory pool.
+ This can result in a significant I/O reduction on swap device and,
+ in the case where decompressing from RAM is faster that swap device
+ reads, can also improve workload performance.
+
+ This is marked experimental because it is a new feature (as of
+ v3.11) that interacts heavily with memory reclaim. While these
+ interactions don't cause any known issues on simple memory setups,
+ they have not be fully explored on the large set of potential
+ configurations and workloads that exist.
+
+choice
+ prompt "Compressed cache for swap pages default compressor"
+ depends on ZSWAP
+ default ZSWAP_COMPRESSOR_DEFAULT_LZO
+ help
+ Selects the default compression algorithm for the compressed cache
+ for swap pages.
+
+ For an overview what kind of performance can be expected from
+ a particular compression algorithm please refer to the benchmarks
+ available at the following LWN page:
+ https://lwn.net/Articles/751795/
+
+ If in doubt, select 'LZO'.
+
+ The selection made here can be overridden by using the kernel
+ command line 'zswap.compressor=' option.
+
+config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
+ bool "Deflate"
+ select CRYPTO_DEFLATE
+ help
+ Use the Deflate algorithm as the default compression algorithm.
+
+config ZSWAP_COMPRESSOR_DEFAULT_LZO
+ bool "LZO"
+ select CRYPTO_LZO
+ help
+ Use the LZO algorithm as the default compression algorithm.
+
+config ZSWAP_COMPRESSOR_DEFAULT_842
+ bool "842"
+ select CRYPTO_842
+ help
+ Use the 842 algorithm as the default compression algorithm.
+
+config ZSWAP_COMPRESSOR_DEFAULT_LZ4
+ bool "LZ4"
+ select CRYPTO_LZ4
+ help
+ Use the LZ4 algorithm as the default compression algorithm.
+
+config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
+ bool "LZ4HC"
+ select CRYPTO_LZ4HC
+ help
+ Use the LZ4HC algorithm as the default compression algorithm.
+
+config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
+ bool "zstd"
+ select CRYPTO_ZSTD
+ help
+ Use the zstd algorithm as the default compression algorithm.
+endchoice
+
+config ZSWAP_COMPRESSOR_DEFAULT
+ string
+ depends on ZSWAP
+ default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
+ default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
+ default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
+ default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
+ default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
+ default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
+ default ""
+
+choice
+ prompt "Compressed cache for swap pages default allocator"
+ depends on ZSWAP
+ default ZSWAP_ZPOOL_DEFAULT_ZBUD
+ help
+ Selects the default allocator for the compressed cache for
+ swap pages.
+ The default is 'zbud' for compatibility, however please do
+ read the description of each of the allocators below before
+ making a right choice.
+
+ The selection made here can be overridden by using the kernel
+ command line 'zswap.zpool=' option.
+
+config ZSWAP_ZPOOL_DEFAULT_ZBUD
+ bool "zbud"
+ select ZBUD
+ help
+ Use the zbud allocator as the default allocator.
+
+config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
+ bool "z3fold"
+ select Z3FOLD
+ help
+ Use the z3fold allocator as the default allocator.
+
+config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
+ bool "zsmalloc"
+ select ZSMALLOC
+ help
+ Use the zsmalloc allocator as the default allocator.
+endchoice
+
+config ZSWAP_ZPOOL_DEFAULT
+ string
+ depends on ZSWAP
+ default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
+ default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
+ 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
+ help
+ A special purpose allocator for storing compressed pages.
+ It is designed to store up to two compressed pages per physical
+ page. While this design limits storage density, it has simple and
+ deterministic reclaim properties that make it preferable to a higher
+ density approach when reclaim will be used.
+
+config Z3FOLD
+ tristate "Up to 3x density storage for compressed pages"
+ depends on ZPOOL
+ help
+ A special purpose allocator for storing compressed pages.
+ It is designed to store up to three compressed pages per physical
+ page. It is a ZBUD derivative so the simplicity and determinism are
+ still there.
+
+config ZSMALLOC
+ tristate "Memory allocator for compressed pages"
+ 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.
+
+config ZSMALLOC_STAT
+ bool "Export zsmalloc statistics"
+ depends on ZSMALLOC
+ select DEBUG_FS
+ help
+ This option enables code in the zsmalloc to collect various
+ statistics about what's happening in zsmalloc and exports that
+ information to userspace via debugfs.
+ If unsure, say N.
+
+menu "SLAB allocator options"
+
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