f55bb154ec
This change reduces the cost of partition index page construction and
LSA migration. This is achieved by several things working together:
- index entries don't store keys as separate small objects (managed_bytes)
They are written into one managed_bytes fragmented storage, entries
hold offset into it.
Before, we paid 16 bytes for managed_bytes plus LSA descriptor for
the storage (1 byte) plus back-reference in the storage (8 bytes),
so 25 bytes. Now we only pay 4 bytes for the size offset. If keys are 16
bytes, that's a reduction from 31 bytes to 20 bytes per key.
- index entries and key storage are now trivially moveable, so LSA
migration can use memcpy() which amortizes the cost per key.
memcpy().
LSA eviction is now trivial and constant time for the whole page
regardless of the number of entries. Page eviction dropped from
14 us to 1 us.
This improves throughput in a CPU-bound miss-heavy read workload where
the partition index doesn't fit in memory.
scylla perf-simple-query -c1 -m200M --partitions=1000000
Before:
15328.25 tps (150.0 allocs/op, 14.1 logallocs/op, 45.4 tasks/op, 286769 insns/op, 218134 cycles/op, 0 errors)
15279.01 tps (149.9 allocs/op, 14.1 logallocs/op, 45.3 tasks/op, 287696 insns/op, 218637 cycles/op, 0 errors)
15347.78 tps (149.7 allocs/op, 14.1 logallocs/op, 45.3 tasks/op, 285851 insns/op, 217795 cycles/op, 0 errors)
15403.68 tps (149.6 allocs/op, 14.1 logallocs/op, 45.2 tasks/op, 285111 insns/op, 216984 cycles/op, 0 errors)
15189.47 tps (150.0 allocs/op, 14.1 logallocs/op, 45.5 tasks/op, 289509 insns/op, 219602 cycles/op, 0 errors)
15295.04 tps (149.8 allocs/op, 14.1 logallocs/op, 45.3 tasks/op, 288021 insns/op, 218545 cycles/op, 0 errors)
15162.01 tps (149.8 allocs/op, 14.1 logallocs/op, 45.4 tasks/op, 291265 insns/op, 220451 cycles/op, 0 errors)
After:
21620.18 tps (148.4 allocs/op, 13.4 logallocs/op, 43.7 tasks/op, 176817 insns/op, 153183 cycles/op, 0 errors)
20644.03 tps (149.8 allocs/op, 13.5 logallocs/op, 44.3 tasks/op, 187941 insns/op, 160409 cycles/op, 0 errors)
20588.06 tps (150.1 allocs/op, 13.5 logallocs/op, 44.5 tasks/op, 188090 insns/op, 160818 cycles/op, 0 errors)
20789.29 tps (149.5 allocs/op, 13.5 logallocs/op, 44.2 tasks/op, 186495 insns/op, 159382 cycles/op, 0 errors)
20977.89 tps (149.5 allocs/op, 13.4 logallocs/op, 44.2 tasks/op, 183969 insns/op, 158140 cycles/op, 0 errors)
21125.34 tps (149.1 allocs/op, 13.4 logallocs/op, 44.1 tasks/op, 183204 insns/op, 156925 cycles/op, 0 errors)
21244.42 tps (148.6 allocs/op, 13.4 logallocs/op, 43.8 tasks/op, 181276 insns/op, 155973 cycles/op, 0 errors)
Mostly because the index now fits in memory.
When it doesn't, the benefits are still visible due to lower LSA overhead.
Scylla in-source tests.
For details on how to run the tests, see docs/dev/testing.md
Shared C++ utils, libraries are in lib/, for Python - pylib/
alternator - Python tests which connect to a single server and use the DynamoDB API unit, boost, raft - unit tests in C++ cqlpy - Python tests which connect to a single server and use CQL topology* - tests that set up clusters and add/remove nodes cql - approval tests that use CQL and pre-recorded output rest_api - tests for Scylla REST API Port 9000 scylla-gdb - tests for scylla-gdb.py helper script nodetool - tests for C++ implementation of nodetool
If you can use an existing folder, consider adding your test to it. New folders should be used for new large categories/subsystems, or when the test environment is significantly different from some existing suite, e.g. you plan to start scylladb with different configuration, and you intend to add many tests and would like them to reuse an existing Scylla cluster (clusters can be reused for tests within the same folder).
To add a new folder, create a new directory, and then
copy & edit its suite.ini.