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linux/drivers/block/zram/Kconfig
Sergey Senozhatsky 84b33bf788 zram: introduce recompress sysfs knob
Allow zram to recompress (using secondary compression streams)
pages.

Re-compression algorithms (we support up to 3 at this stage)
are selected via recomp_algorithm:

  echo "algo=zstd priority=1" > /sys/block/zramX/recomp_algorithm

Please read documentation for more details.

We support several recompression modes:

1) IDLE pages recompression is activated by `idle` mode

  echo "type=idle" > /sys/block/zram0/recompress

2) Since there may be many idle pages user-space may pass a size
threshold value (in bytes) and we will recompress pages only
of equal or greater size:

  echo "threshold=888" > /sys/block/zram0/recompress

3) HUGE pages recompression is activated by `huge` mode

  echo "type=huge" > /sys/block/zram0/recompress

4) HUGE_IDLE pages recompression is activated by `huge_idle` mode

  echo "type=huge_idle" > /sys/block/zram0/recompress

[senozhatsky@chromium.org: we should always zero out err variable in recompress loop[
  Link: https://lkml.kernel.org/r/20221110143423.3250790-1-senozhatsky@chromium.org
Link: https://lkml.kernel.org/r/20221109115047.2921851-5-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-11-30 15:58:51 -08:00

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# SPDX-License-Identifier: GPL-2.0
config ZRAM
tristate "Compressed RAM block device support"
depends on BLOCK && SYSFS && MMU
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
itself. These disks allow very fast I/O and compression provides
good amounts of memory savings.
It has several use cases, for example: /tmp storage, use as swap
disks and maybe many more.
See Documentation/admin-guide/blockdev/zram.rst for more information.
choice
prompt "Default zram compressor"
default ZRAM_DEF_COMP_LZORLE
depends on ZRAM
config ZRAM_DEF_COMP_LZORLE
bool "lzo-rle"
depends on CRYPTO_LZO
config ZRAM_DEF_COMP_ZSTD
bool "zstd"
depends on CRYPTO_ZSTD
config ZRAM_DEF_COMP_LZ4
bool "lz4"
depends on CRYPTO_LZ4
config ZRAM_DEF_COMP_LZO
bool "lzo"
depends on CRYPTO_LZO
config ZRAM_DEF_COMP_LZ4HC
bool "lz4hc"
depends on CRYPTO_LZ4HC
config ZRAM_DEF_COMP_842
bool "842"
depends on CRYPTO_842
endchoice
config ZRAM_DEF_COMP
string
default "lzo-rle" if ZRAM_DEF_COMP_LZORLE
default "zstd" if ZRAM_DEF_COMP_ZSTD
default "lz4" if ZRAM_DEF_COMP_LZ4
default "lzo" if ZRAM_DEF_COMP_LZO
default "lz4hc" if ZRAM_DEF_COMP_LZ4HC
default "842" if ZRAM_DEF_COMP_842
config ZRAM_WRITEBACK
bool "Write back incompressible or idle page to backing device"
depends on ZRAM
help
With incompressible page, there is no memory saving to keep it
in memory. Instead, write it out to backing device.
For this feature, admin should set up backing device via
/sys/block/zramX/backing_dev.
With /sys/block/zramX/{idle,writeback}, application could ask
idle page's writeback to the backing device to save in memory.
See Documentation/admin-guide/blockdev/zram.rst for more information.
config ZRAM_MEMORY_TRACKING
bool "Track zRam block status"
depends on ZRAM && DEBUG_FS
help
With this feature, admin can track the state of allocated blocks
of zRAM. Admin could see the information via
/sys/kernel/debug/zram/zramX/block_state.
See Documentation/admin-guide/blockdev/zram.rst for more information.
config ZRAM_MULTI_COMP
bool "Enable multiple compression streams"
depends on ZRAM
help
This will enable multi-compression streams, so that ZRAM can
re-compress pages using a potentially slower but more effective
compression algorithm. Note, that IDLE page recompression
requires ZRAM_MEMORY_TRACKING.