Jon Haddad created CASSANDRA-19979:
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Summary: Use internal buffer on streaming slow path
Key: CASSANDRA-19979
URL: https://issues.apache.org/jira/browse/CASSANDRA-19979
Project: Cassandra
Issue Type: Improvement
Reporter: Jon Haddad
Attachments: image-2024-10-04-12-40-26-727.png
CASSANDRA-15452 is introducing an internal buffer to compaction in order to
increase throughput while reducing IOPS. We can do the same thing with our
streaming slow path. There's a common misconception that the overhead comes
from serde overhead, but I've found on a lot of devices the overhead is due to
our read patterns. This is most commonly found on non-NVMe drives, especially
disaggregated storage such as EBS where the latency is higher and more variable.
Attached is a perf profile showing the cost of streaming is dominated by pread.
The team I was working with was seeing they could stream only 12MB per
streaming session. Reducing the number of read operations by using internal
buffered reads should improve this by at least 3-5x, as well as reduce CPU
overhead from reduced system calls.
!image-2024-10-04-12-40-26-727.png!
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