linux.git/Documentation/admin-guide/blockdev/zram.rst, branch v6.12

zram: support priority parameter in recompression

2024-09-09T23:39:12+00:00

recompress device attribute supports alg=NAME parameter so that we can
specify only one particular algorithm we want to perform recompression
with.  However, with algo params we now can have several exactly same
secondary algorithms but each with its own params tuning (e.g.  priority 1
configured to use more aggressive level, and priority 2 configured to use
a pre-trained dictionary).  Support priority=NUM parameter so that we can
correctly determine which secondary algorithm we want to use.

Link: https://lkml.kernel.org/r/20240902105656.1383858-25-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Cc: Minchan Kim 
Cc: Nick Terrell 
Signed-off-by: Andrew Morton

Documentation/zram: add documentation for algorithm parameters

2024-09-09T23:39:11+00:00

Document brief description of compression algorithms' parameters:
compression level and pre-trained dictionary.

[senozhatsky@chromium.org: trivial fixup]
  Link: https://lkml.kernel.org/r/20240903063722.1603592-1-senozhatsky@chromium.org
Link: https://lkml.kernel.org/r/20240902105656.1383858-24-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Cc: Minchan Kim 
Cc: Nick Terrell 
Signed-off-by: Andrew Morton

zram: introduce algorithm_params device attribute

2024-09-09T23:39:09+00:00

This attribute is used to setup compression algorithms' parameters, so we
can tweak algorithms' characteristics.  At this point only 'level' is
supported (to be extended in the future).

Each call sets up parameters for one particular algorithm, which should be
specified either by the algorithm's priority or algo name.  This is
expected to be called after corresponding algorithm is selected via
comp_algorithm or recomp_algorithm.

 echo "priority=0 level=1" > /sys/block/zram0/algorithm_params
or
 echo "algo=zstd level=1" > /sys/block/zram0/algorithm_params

Link: https://lkml.kernel.org/r/20240902105656.1383858-16-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Cc: Minchan Kim 
Cc: Nick Terrell 
Signed-off-by: Andrew Morton

zram: introduce custom comp backends API

2024-09-09T23:39:07+00:00

Moving to custom backends implementation gives us ability to have our own
minimalistic and extendable API, and algorithms tunings becomes possible.

The list of compression backends is empty at this point, we will add
backends in the followup patches.

Link: https://lkml.kernel.org/r/20240902105656.1383858-5-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Cc: Minchan Kim 
Cc: Nick Terrell 
Signed-off-by: Andrew Morton

zram: add max_pages param to recompression

2024-04-26T03:56:30+00:00

Introduce "max_pages" param to recompress device attribute which sets an
upper limit on the number of entries (pages) zram attempts to recompress
(in this particular recompression call).  S/W recompression can be quite
expensive so limiting the number of pages recompress touches can be quite
helpful.

Link: https://lkml.kernel.org/r/20240329094050.2815699-1-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Acked-by: Brian Geffon 
Cc: Minchan Kim 
Signed-off-by: Andrew Morton

zram: split memory-tracking and ac-time tracking

2023-12-11T00:51:40+00:00

ZRAM_MEMORY_TRACKING enables two features:
- per-entry ac-time tracking
- debugfs interface

The latter one is the reason why memory-tracking depends on DEBUG_FS,
while the former one is used far beyond debugging these days.  Namely
ac-time is used for fine grained writeback of idle entries (pages).

Move ac-time tracking under its own config option so that it can be
enabled (along with writeback) on systems without DEBUG_FS.

[senozhatsky@chromium.org: ifdef fixup, per Dmytro]
  Link: https://lkml.kernel.org/r/20231117013543.540280-1-senozhatsky@chromium.org
Link: https://lkml.kernel.org/r/20231115024223.4133148-1-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Cc: Minchan Kim 
Cc: Dmytro Maluka 
Signed-off-by: Andrew Morton

zram: add incompressible flag to read_block_state()

2022-11-30T23:58:53+00:00

Add a new flag to zram block state that shows if the page is
incompressible: that none of the algorithm (including secondary ones)
could compress it.

Link: https://lkml.kernel.org/r/20221109115047.2921851-14-senozhatsky@chromium.org
Suggested-by: Minchan Kim 
Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Alexey Romanov 
Cc: Nhat Pham 
Cc: Nitin Gupta 
Cc: Suleiman Souhlal 
Signed-off-by: Andrew Morton

zram: add incompressible writeback

2022-11-30T23:58:53+00:00

Add support for incompressible pages writeback:

  echo incompressible > /sys/block/zramX/writeback

Link: https://lkml.kernel.org/r/20221109115047.2921851-13-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Alexey Romanov 
Cc: Nhat Pham 
Cc: Nitin Gupta 
Cc: Suleiman Souhlal 
Signed-off-by: Andrew Morton

documentation: add zram recompression documentation

2022-11-30T23:58:52+00:00

Document user-space visible device attributes that are enabled by
ZRAM_MULTI_COMP.

Link: https://lkml.kernel.org/r/20221109115047.2921851-12-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Alexey Romanov 
Cc: Nhat Pham 
Cc: Nitin Gupta 
Cc: Suleiman Souhlal 
Signed-off-by: Andrew Morton

zram: add recompress flag to read_block_state()

2022-11-30T23:58:51+00:00

Add a new flag to zram block state that shows if the page was recompressed
(using alternative compression algorithm).

Link: https://lkml.kernel.org/r/20221109115047.2921851-6-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Acked-by: Minchan Kim 
Cc: Alexey Romanov 
Cc: Nhat Pham 
Cc: Nitin Gupta 
Cc: Suleiman Souhlal 
Signed-off-by: Andrew Morton