Re: [PATCHv5 00/13] zram: Support multiple compression streams

[Minchan Kim <minchan@kernel.org>]

On Wed, Nov 09, 2022 at 08:50:34PM +0900, Sergey Senozhatsky wrote:
> Hello,
> 
> 	This series adds support for multiple compression streams.
> 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 deflate 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.
> 
> v5:
> -- Addressed (very valuable) review feedback from Minchan
> -- Extended documentation
> -- We now do chain recompression, tryin algos in order of their priority
> -- Support up to 4 compression streams
> -- Added named parameters to recomp_algorithm and recompress sysfs knobs
> -- Cherry-picked patch from Alexey
> -- Store algo priority in mete flags
> -- Renamed some fo the flags
> -- Added incompressible bit to block state output
> -- Added incompressible writeback
> -- etc.
> 
> v4:
> -- added IS_ERR_VALUE patch (Andrew)
> -- documented SIZE units (bytes) (Andrew)
> -- re-phrased writeback BIO error comment (Andrew)
> -- return zs_malloc() error code from zram_recompress()
> -- do not lose zram_recompress() error in recompress_store()
> -- corrected a typo
> -- fixed previous rebase errors
> -- rebased the series
> 
> v3:
> -- conditionally reschedule during recompression loop so that
>    we don't stall RCU grace periods
> -- fixed a false-positive WARN_ON
> 
> v2:
> -- rebased
> -- mark completely incompressible pages (neither default nor secondary
>    algorithm can compress them) with a new flag so that we don't attempt
>    to recompress them all the time
> 
> Alexey Romanov (1):
>   zram: add size class equals check into recompression
> 
> Sergey Senozhatsky (12):
>   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
>   zram: Add recompress flag to read_block_state()
>   zram: Clarify writeback_store() comment
>   zram: Use IS_ERR_VALUE() to check for zs_malloc() errors
>   zram: remove redundant checks from zram_recompress()
>   zram: Add algo parameter support to zram_recompress()
>   documentation: Add zram recompression documentation
>   zram: add incompressible writeback
>   zram: Add incompressible flag to read_block_state()
> 
>  Documentation/admin-guide/blockdev/zram.rst | 100 +++-
>  drivers/block/zram/Kconfig                  |   9 +
>  drivers/block/zram/zcomp.c                  |   6 +-
>  drivers/block/zram/zcomp.h                  |   2 +-
>  drivers/block/zram/zram_drv.c               | 604 +++++++++++++++++---
>  drivers/block/zram/zram_drv.h               |  22 +-
>  include/linux/zsmalloc.h                    |   2 +
>  mm/zsmalloc.c                               |  21 +
>  8 files changed, 685 insertions(+), 81 deletions(-)

Acked-by: Minchan Kim <minchan@kernel.org>

Thanks!