47efbdffbc
Range tombstones are represented as entry attributes, which applies to
the interval between entries. So if a range tombstone covers many
rows, to apply it we have to update all covered entries. In some
workloads that could be many entries, even the whole cache. Before
the patch, we did this update without preemption, which can cause
reactor stalls in such workloads.
This scenario is already covered by mvcc_tests,
e.g. test_apply_to_incomplete_respects_continuity. And I verified that
the new preemption point is hit in the test.
perf-row-cache-update results show no significant stalls anymore (max
2ms scheduling delay, instead of previous 1.5 s):
Generated 1124195 rows
Memtable fill took 4179.457520 [ms], {count: 8295, 99%: 0.654949 [ms], max: 32.817176 [ms]}
Draining...
took 0.000616 [ms]
cache: 2506/2948 [MB], memtable: 781/1024 [MB], alloc/comp: 1051/662 [MB] (amp: 0.630)
update: 2874.157471 [ms], preemption: {count: 26650, 99%: 1.131752 [ms], max: 2.068762 [ms]}, cache: 3027/3973 [MB], alloc/comp: 3951/2424 [MB] (amp: 0.614), pr/me/dr 1124195/0/0
Fixes #23479
Fixes #2578
Closes scylladb/scylladb#27469
* github.com:scylladb/scylladb:
cache, mvcc: Preempt cache update when applying range tombstone from memtable
partition_snapshot_row_cursor: Clarify non-obvious semantic difference of range_tombstone()
perf-row-cache-update: Add scenario with large tombstone covering many rows
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.