linux-toradex.git/drivers/block/zram/backend_zstd.c, branch v6.13-rc2

zram: add dictionary support to zstd backend

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

This adds support for pre-trained zstd dictionaries [1] Dictionary is
setup in params once (per-comp) and loaded to Cctx and Dctx by reference,
so we don't allocate extra memory.

TEST
====

*** zstd
/sys/block/zram0/mm_stat
1750654976 504565092 514203648        0 514203648        1        0    34204    34204

*** zstd dict=/etc/zstd-dict-amd64
/sys/block/zram0/mm_stat
1750638592 465851259 475373568        0 475373568        1        0    34185    34185

*** zstd level=8 dict=/etc/zstd-dict-amd64
/sys/block/zram0/mm_stat
1750642688 430765171 439955456        0 439955456        1        0    34185    34185

[1] https://github.com/facebook/zstd/blob/dev/programs/zstd.1.md#dictionary-builder

Link: https://lkml.kernel.org/r/20240902105656.1383858-23-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Cc: Minchan Kim 
Cc: Nick Terrell 
Signed-off-by: Andrew Morton

zram: move immutable comp params away from per-CPU context

2024-09-09T23:39:10+00:00

Immutable params never change once comp has been allocated and setup, so
we don't need to store multiple copies of them in each per-CPU backend
context.  Move those to per-comp zcomp_params and pass it to backends
callbacks for requests execution.  Basically, this means parameters
sharing between different contexts.

Also introduce two new backends callbacks: setup_params() and
release_params().  First, we need to validate params in a driver-specific
way; second, driver may want to allocate its specific representation of
the params which is needed to execute requests.

Link: https://lkml.kernel.org/r/20240902105656.1383858-20-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Cc: Minchan Kim 
Cc: Nick Terrell 
Signed-off-by: Andrew Morton

zram: introduce zcomp_ctx structure

2024-09-09T23:39:10+00:00

Keep run-time driver data (scratch buffers, etc.) in zcomp_ctx structure. 
This structure is allocated per-CPU because drivers (backends) need to
modify its content during requests execution.

We will split mutable and immutable driver data, this is a preparation
path.

Link: https://lkml.kernel.org/r/20240902105656.1383858-19-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Cc: Minchan Kim 
Cc: Nick Terrell 
Signed-off-by: Andrew Morton

zram: introduce zcomp_req structure

2024-09-09T23:39:10+00:00

Encapsulate compression/decompression data in zcomp_req structure.

Link: https://lkml.kernel.org/r/20240902105656.1383858-18-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Cc: Minchan Kim 
Cc: Nick Terrell 
Signed-off-by: Andrew Morton

zram: recalculate zstd compression params once

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

zstd compression params depends on level, but are constant for a given
instance of zstd compression backend.  Calculate once (during ctx
creation).

Link: https://lkml.kernel.org/r/20240902105656.1383858-15-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Cc: Minchan Kim 
Cc: Nick Terrell 
Signed-off-by: Andrew Morton

zram: introduce zcomp_params structure

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

We will store a per-algorithm parameters there (compression level,
dictionary, dictionary size, etc.).

Link: https://lkml.kernel.org/r/20240902105656.1383858-14-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Cc: Minchan Kim 
Cc: Nick Terrell 
Signed-off-by: Andrew Morton

zram: pass estimated src size hint to zstd

2024-09-09T23:39:08+00:00

zram works with PAGE_SIZE buffers, so we always know exact size of the
source buffer and hence can pass estimated_src_size to zstd_get_params().

This hint on x86_64, for example, reduces the size of the work memory
buffer from 1303520 bytes down to 90080 bytes.  Given that compression
streams are per-CPU that's quite some memory saving.

Link: https://lkml.kernel.org/r/20240902105656.1383858-10-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Cc: Minchan Kim 
Cc: Nick Terrell 
Signed-off-by: Andrew Morton

zram: add zstd compression backend support

2024-09-09T23:39:08+00:00

Add s/w zstd compression.

Link: https://lkml.kernel.org/r/20240902105656.1383858-9-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky 
Cc: Minchan Kim 
Cc: Nick Terrell 
Signed-off-by: Andrew Morton