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Huang Jianan 5d50538fc5 erofs: support adjust lz4 history window size
lz4 uses LZ4_DISTANCE_MAX to record history preservation. When
using rolling decompression, a block with a higher compression
ratio will cause a larger memory allocation (up to 64k). It may
cause a large resource burden in extreme cases on devices with
small memory and a large number of concurrent IOs. So appropriately
reducing this value can improve performance.

Decreasing this value will reduce the compression ratio (except
when input_size <LZ4_DISTANCE_MAX). But considering that erofs
currently only supports 4k output, reducing this value will not
significantly reduce the compression benefits.

The maximum value of LZ4_DISTANCE_MAX defined by lz4 is 64k, and
we can only reduce this value. For the old kernel, it just can't
reduce the memory allocation during rolling decompression without
affecting the decompression result.

Link: https://lore.kernel.org/r/20210329012308.28743-3-hsiangkao@aol.com
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Huang Jianan <huangjianan@oppo.com>
Signed-off-by: Guo Weichao <guoweichao@oppo.com>
[ Gao Xiang: introduce struct erofs_sb_lz4_info for configurations. ]
Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
2021-03-29 10:24:58 +08:00
arch Two fixes: 2021-03-28 12:19:16 -07:00
block block: don't create too many partitions 2021-03-27 09:22:18 -06:00
certs
crypto
Documentation
drivers A fix for auxdisplay: 2021-03-28 13:20:38 -07:00
fs erofs: support adjust lz4 history window size 2021-03-29 10:24:58 +08:00
include Fix the non-debug mutex_lock_io_nested() method to map to mutex_lock_io() instead of mutex_lock(). 2021-03-28 12:12:22 -07:00
init
ipc
kernel io_uring-5.12-2021-03-27 2021-03-28 11:42:05 -07:00
lib
LICENSES
mm
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samples
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tools Some more perf tools fixes for v5.12: 2021-03-28 13:22:54 -07:00
usr
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.cocciconfig
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Makefile Linux 5.12-rc5 2021-03-28 15:48:16 -07:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.