Hello, RFC series that adds support for multiple (per-CPU) compression streams (at point only 2). The main idea is that different compression algorithms have different characteristics and zram may benefit when it uses a combination of algorithms: a default algorithm that is faster but have lower compression rate and a secondary algorithm that can use higher compression rate at a price of slower compression/decompression. There are several use-case for this functionality: - huge pages re-compression: zstd or defalte can successfully compress huge pages (~50% of huge pages on my synthetic ChromeOS tests), IOW pages that lzo was not able to compress. - idle pages re-compression: idle/cold pages sit in the memory and we may reduce zsmalloc memory usage if we recompress those idle pages. User-space has a number of ways to control the behavior and impact of zram recompression: what type of pages should be recompressed, size watermarks, etc. Please refer to documentation patch. Sergey Senozhatsky (7): zram: Preparation for multi-zcomp support zram: Add recompression algorithm sysfs knob zram: Factor out WB and non-WB zram read functions zram: Introduce recompress sysfs knob documentation: Add recompression documentation zram: Add recompression algorithm choice to Kconfig zram: Add recompress flag to read_block_state() Documentation/admin-guide/blockdev/zram.rst | 64 ++- drivers/block/zram/Kconfig | 51 +++ drivers/block/zram/zcomp.c | 6 +- drivers/block/zram/zcomp.h | 2 +- drivers/block/zram/zram_drv.c | 432 +++++++++++++++++--- drivers/block/zram/zram_drv.h | 15 +- 6 files changed, 504 insertions(+), 66 deletions(-) -- 2.37.2.789.g6183377224-goog
