Kconfig

  1# SPDX-License-Identifier: GPL-2.0
  2config ZRAM
  3	tristate "Compressed RAM block device support"
  4	depends on BLOCK && SYSFS && MMU
  5	select ZSMALLOC
  6	help
  7	  Creates virtual block devices called /dev/zramX (X = 0, 1, ...).
  8	  Pages written to these disks are compressed and stored in memory
  9	  itself. These disks allow very fast I/O and compression provides
 10	  good amounts of memory savings.
 11
 12	  It has several use cases, for example: /tmp storage, use as swap
 13	  disks and maybe many more.
 14
 15	  See Documentation/admin-guide/blockdev/zram.rst for more information.
 16
 17config ZRAM_BACKEND_LZ4
 18	bool "lz4 compression support"
 19	depends on ZRAM
 20	select LZ4_COMPRESS
 21	select LZ4_DECOMPRESS
 22
 23config ZRAM_BACKEND_LZ4HC
 24	bool "lz4hc compression support"
 25	depends on ZRAM
 26	select LZ4HC_COMPRESS
 27	select LZ4_DECOMPRESS
 28
 29config ZRAM_BACKEND_ZSTD
 30	bool "zstd compression support"
 31	depends on ZRAM
 32	select ZSTD_COMPRESS
 33	select ZSTD_DECOMPRESS
 34
 35config ZRAM_BACKEND_DEFLATE
 36	bool "deflate compression support"
 37	depends on ZRAM
 38	select ZLIB_DEFLATE
 39	select ZLIB_INFLATE
 40
 41config ZRAM_BACKEND_842
 42	bool "842 compression support"
 43	depends on ZRAM
 44	select 842_COMPRESS
 45	select 842_DECOMPRESS
 46
 47config ZRAM_BACKEND_FORCE_LZO
 48	depends on ZRAM
 49	def_bool !ZRAM_BACKEND_LZ4 && !ZRAM_BACKEND_LZ4HC && \
 50		!ZRAM_BACKEND_ZSTD && !ZRAM_BACKEND_DEFLATE && \
 51		!ZRAM_BACKEND_842
 52
 53config ZRAM_BACKEND_LZO
 54	bool "lzo and lzo-rle compression support" if !ZRAM_BACKEND_FORCE_LZO
 55	depends on ZRAM
 56	default ZRAM_BACKEND_FORCE_LZO
 57	select LZO_COMPRESS
 58	select LZO_DECOMPRESS
 59
 60choice
 61	prompt "Default zram compressor"
 62	default ZRAM_DEF_COMP_LZORLE
 63	depends on ZRAM
 64
 65config ZRAM_DEF_COMP_LZORLE
 66	bool "lzo-rle"
 67	depends on ZRAM_BACKEND_LZO
 68
 69config ZRAM_DEF_COMP_LZO
 70	bool "lzo"
 71	depends on ZRAM_BACKEND_LZO
 72
 73config ZRAM_DEF_COMP_LZ4
 74	bool "lz4"
 75	depends on ZRAM_BACKEND_LZ4
 76
 77config ZRAM_DEF_COMP_LZ4HC
 78	bool "lz4hc"
 79	depends on ZRAM_BACKEND_LZ4HC
 80
 81config ZRAM_DEF_COMP_ZSTD
 82	bool "zstd"
 83	depends on ZRAM_BACKEND_ZSTD
 84
 85config ZRAM_DEF_COMP_DEFLATE
 86	bool "deflate"
 87	depends on ZRAM_BACKEND_DEFLATE
 88
 89config ZRAM_DEF_COMP_842
 90	bool "842"
 91	depends on ZRAM_BACKEND_842
 92
 93endchoice
 94
 95config ZRAM_DEF_COMP
 96	string
 97	depends on ZRAM
 98	default "lzo-rle" if ZRAM_DEF_COMP_LZORLE
 99	default "lzo" if ZRAM_DEF_COMP_LZO
100	default "lz4" if ZRAM_DEF_COMP_LZ4
101	default "lz4hc" if ZRAM_DEF_COMP_LZ4HC
102	default "zstd" if ZRAM_DEF_COMP_ZSTD
103	default "deflate" if ZRAM_DEF_COMP_DEFLATE
104	default "842" if ZRAM_DEF_COMP_842
105	default "unset-value"
106
107config ZRAM_WRITEBACK
108       bool "Write back incompressible or idle page to backing device"
109       depends on ZRAM
110       help
111	 This lets zram entries (incompressible or idle pages) be written
112	 back to a backing device, helping save memory.
113	 For this feature, admin should set up backing device via
114	 /sys/block/zramX/backing_dev.
115
116	 With /sys/block/zramX/{idle,writeback}, application could ask
117	 idle page's writeback to the backing device to save in memory.
118
119	 See Documentation/admin-guide/blockdev/zram.rst for more information.
120
121config ZRAM_TRACK_ENTRY_ACTIME
122	bool "Track access time of zram entries"
123	depends on ZRAM
124	help
125	  With this feature zram tracks access time of every stored
126	  entry (page), which can be used for a more fine grained IDLE
127	  pages writeback.
128
129config ZRAM_MEMORY_TRACKING
130	bool "Track zRam block status"
131	depends on ZRAM && DEBUG_FS
132	select ZRAM_TRACK_ENTRY_ACTIME
133	help
134	  With this feature, admin can track the state of allocated blocks
135	  of zRAM. Admin could see the information via
136	  /sys/kernel/debug/zram/zramX/block_state.
137
138	  See Documentation/admin-guide/blockdev/zram.rst for more information.
139
140config ZRAM_MULTI_COMP
141	bool "Enable multiple compression streams"
142	depends on ZRAM
143	help
144	  This will enable multi-compression streams, so that ZRAM can
145	  re-compress pages using a potentially slower but more effective
146	  compression algorithm. Note, that IDLE page recompression
147	  requires ZRAM_TRACK_ENTRY_ACTIME.