Dipietro Salvatore created CASSANDRA-19429:
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Summary: Remove lock contention generated by getCapacity function
in SSTableReader
Key: CASSANDRA-19429
URL: https://issues.apache.org/jira/browse/CASSANDRA-19429
Project: Cassandra
Issue Type: Bug
Reporter: Dipietro Salvatore
Attachments: asprof_cass4.1.3__lock_20240216052912lock.html
Profiling Cassandra 4.1.3 on large AWS instances, a high number of lock
acquires is measured in the `getCapacity` function from
`org/apache/cassandra/cache/InstrumentingCache` (1.9M lock acquires per 60
seconds). Based on our tests on r8g.24xlarge instances (using Ubuntu 22.04),
this limits the CPU utilization of the system to under 50% when testing at full
load and therefore limits the achieved throughput.
Removing the lock contention from the SSTableReader.java file by replacing the
call to `getCapacity` with `size` achieves up to 2.95x increase in throughput
on r8g.24xlarge and 2x on r7i.24xlarge:
| Instance type | Cass 4.1.3 | Cass 4.1.3 patched |
| ------------- | ---------- | ------------------ |
| r8g.24xlarge | 168k ops | 496k ops (2.95x) |
| r7i.24xlarge | 153k ops | 304k ops (1.98x) |
Instructions to reproduce:
```bash
## Requirements for Ubuntu 22.04
sudo apt install -y ant git openjdk-11-jdk
## Build and run
CASSANDRA_USE_JDK11=true ant realclean && CASSANDRA_USE_JDK11=true ant jar &&
CASSANDRA_USE_JDK11=true ant stress-build && rm -rf data && bin/cassandra -f -R
# Run
bin/cqlsh -e 'drop table if exists keyspace1.standard1;' && \
bin/cqlsh -e 'drop keyspace if exists keyspace1;' && \
bin/nodetool clearsnapshot --all && tools/bin/cassandra-stress write n=10000000
cl=ONE -rate threads=384 -node 127.0.0.1 -log file=cload.log -graph
file=cload.html && \
bin/nodetool compact keyspace1 && sleep 30s && \
tools/bin/cassandra-stress mixed ratio\(write=10,read=90\) duration=10m cl=ONE
-rate threads=406 -node localhost -log file=result.log -graph file=graph.html
```
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