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"
One part of the improvement comes from replacing zlib's CRC32 with the one
from libdeflate, which is optimized for modern architecture and utilizes the
PCLMUL instruction.
perf_checksum test was introduced to measure performance of various
checksumming operations.
Results for 514 B (relevant for writing with compression enabled):
test iterations median mad min max
crc_test.perf_deflate_crc32_combine 58414 16.711us 3.483ns 16.708us 16.725us
crc_test.perf_adler_combine 165788278 6.059ns 0.031ns 6.027ns 7.519ns
crc_test.perf_zlib_crc32_combine 59546 16.767us 26.191ns 16.741us 16.801us
---
crc_test.perf_deflate_crc32_checksum 12705072 83.267ns 4.580ns 78.687ns 98.964ns
crc_test.perf_adler_checksum 3918014 206.701ns 23.469ns 183.231ns 258.859ns
crc_test.perf_zlib_crc32_checksum 2329682 428.787ns 0.085ns 428.702ns 510.085ns
Results for 64 KB (relevant for writing with compression disabled):
test iterations median mad min max
crc_test.perf_deflate_crc32_combine 25364 38.393us 17.683ns 38.375us 38.545us
crc_test.perf_adler_combine 169797143 5.842ns 0.009ns 5.833ns 6.901ns
crc_test.perf_zlib_crc32_combine 26067 38.663us 95.094ns 38.546us 40.523us
---
crc_test.perf_deflate_crc32_checksum 202821 4.937us 14.426ns 4.912us 5.093us
crc_test.perf_adler_checksum 44684 22.733us 206.263ns 22.492us 25.258us
crc_test.perf_zlib_crc32_checksum 18839 53.049us 36.117ns 53.013us 53.274us
The new CRC32 implementation (deflate_crc32) doesn't provide a fast
checksum_combine() yet, it delegates to zlib so it's as slow as the latter.
Because for CRC32 checksum_combine() is several orders of magnitude slower
than checksum(), we avoid calling checksum_combine() completely for this
checksummer. We still do it for adler32, which has combine() which is faster
than checksum().
SStable write performance was evaluated by running:
perf_fast_forward --populate --data-directory /tmp/perf-mc \
--rows=10000000 -c1 -m4G --datasets small-part
Below is a summary of the average frag/s for a memtable flush. Each result is
an average of about 20 flushes with stddev of about 4k.
Before:
[1] MC,lz4: 330'903
[2] LA,lz4: 450'157
[3] MC,checksum: 419'716
[4] LA,checksum: 459'559
After:
[1'] MC,lz4: 446'917 ([1] + 35%)
[2'] LA,lz4: 456'046 ([2] + 1.3%)
[3'] MC,checksum: 462'894 ([3] + 10%)
[4'] LA,checksum: 467'508 ([4] + 1.7%)
After this series, the performance of the MC format writer is similar to that
of the LA format before the series.
There seems to be a small but consistent improvement for LA too. I'm not sure
why.
"
* tag 'improve-mc-sstable-checksum-libdeflate-v3' of github.com:tgrabiec/scylla:
tests: perf: Introduce perf_checksum
tests: Add test for libdeflate CRC32 implementation
sstables: compress: Use libdeflate for crc32
sstables: compress: Rename crc32_utils to zlib_crc32_checksummer
licenses: Add libdeflate license
Integrate libdeflate with the build system
Add libdeflate submodule
sstables: Avoid checksum_combine() for the crc32 checksummer
sstables: compress: Avoid unnecessary checksum_combine()
sstables: checksum_utils: Add missing include
(cherry picked from commit 5e759b0c07)
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