kernel.git/drivers/block/zram/zcomp.h, branch linux-6.14.y

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

2024-09-09T23:39:10Z

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

2024-09-09T23:39:10Z

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

2024-09-09T23:39:10Z

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: introduce zcomp_params structure

2024-09-09T23:39:09Z

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: introduce custom comp backends API

2024-09-09T23:39:07Z

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: zcomp: remove zcomp_set_max_streams() declaration

2024-03-05T01:01:17Z

The zcomp_set_max_streams() is removed from commit 43209ea2d17a ("zram: remove max_comp_streams internals"), remove the declaration. Link: https://lkml.kernel.org/r/20240223035548.2591882-2-wangkefeng.wang@huawei.com Signed-off-by: Kefeng Wang Cc: Chengming Zhou Cc: Huacai Chen Cc: Johannes Weiner Cc: Minchan Kim Cc: Nhat Pham Cc: Sergey Senozhatsky Cc: Yosry Ahmed Signed-off-by: Andrew Morton

zram: preparation for multi-zcomp support

2022-11-30T23:58:51Z

Patch series "zram: Support multiple compression streams", v5. 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. Userspace 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. This patch (of 13): The patch turns compression streams and compressor algorithm name struct zram members into arrays, so that we can have multiple compression streams support (in the next patches). The patch uses a rather explicit API for compressor selection: - Get primary (default) compression stream zcomp_stream_get(zram->comps[ZRAM_PRIMARY_COMP]) - Get secondary compression stream zcomp_stream_get(zram->comps[ZRAM_SECONDARY_COMP]) We use similar API for compression streams put(). At this point we always have just one compression stream, since CONFIG_ZRAM_MULTI_COMP is not yet defined. Link: https://lkml.kernel.org/r/20221109115047.2921851-1-senozhatsky@chromium.org Link: https://lkml.kernel.org/r/20221109115047.2921851-2-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Acked-by: Minchan Kim Cc: Minchan Kim Cc: Nitin Gupta Cc: Suleiman Souhlal Cc: Nhat Pham Cc: Alexey Romanov Signed-off-by: Andrew Morton

zram: Use local lock to protect per-CPU data

2020-05-28T08:31:10Z

The zcomp driver uses per-CPU compression. The per-CPU data pointer is acquired with get_cpu_ptr() which implicitly disables preemption. It allocates memory inside the preempt disabled region which conflicts with the PREEMPT_RT semantics. Replace the implicit preemption control with an explicit local lock. This allows RT kernels to substitute it with a real per CPU lock, which serializes the access but keeps the code section preemptible. On non RT kernels this maps to preempt_disable() as before, i.e. no functional change. [bigeasy: Use local_lock(), description, drop reordering] Signed-off-by: Mike Galbraith Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra Link: https://lore.kernel.org/r/20200527201119.1692513-8-bigeasy@linutronix.de

zram: Allocate struct zcomp_strm as per-CPU memory

2020-05-28T08:31:10Z

zcomp::stream is a per-CPU pointer, pointing to struct zcomp_strm which contains two pointers. Having struct zcomp_strm allocated directly as per-CPU memory would avoid one additional memory allocation and a pointer dereference. This also simplifies the addition of a local_lock to struct zcomp_strm. Allocate zcomp::stream directly as per-CPU memory. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra Link: https://lore.kernel.org/r/20200527201119.1692513-7-bigeasy@linutronix.de

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

2019-05-30T18:26:32Z

Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 3029 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Allison Randal Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de Signed-off-by: Greg Kroah-Hartman