The zstd implementation of `compressor` has a separate decompression and
compression context per instance. This is unreasonably wasteful. One
decompression buffer and one compression buffer *per shard* is enough.
The waste is significant. There might exist thousands of SSTable readers, each
containing its own instance of `compressor` with several hundred KiB worth of
unneeded buffers. This adds up to gigabytes of wasted memory and gigapascals
of allocator pressure.
This patch modifies the implementation of zstd_processor so that all its
instances on the shard share their contexts.
Fixes#11733
Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
Enable creating shared_ptr<BaseClass> in nonstatic_class_registry
using BaseClass::ptr_type and use that for
abstract_replication_strategy.
While at it, also clean up compressor with that respect
to define compressor::ptr_type as shared_ptr<compressor>
thus simplifying compressor_registry.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
This adds the option to compress sstables using the Zstandard algorithm
(https://facebook.github.io/zstd/).
To use, pass 'sstable_compression': 'org.apache.cassandra.io.compress.ZstdCompressor'
to the 'compression' argument when creating a table.
You can also specify a 'compression_level'. See Zstd documentation for the available
compression levels.
Resolves#2613.
Signed-off-by: Kamil Braun <kbraun@scylladb.com>
