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Jonathan Ellis commented on CASSANDRA-3578: ------------------------------------------- bq. Are you referring to the fact that I always use buffer.capacity() instead of the constant defining their size? No, I'm talking about {code} // Map the segment, extending or truncating it to the standard segment size logFileAccessor.setLength(DatabaseDescriptor.getCommitLogSegmentSize()); {code} There's also {code} // check against SEGMENT_SIZE avoids recycling odd-sized or empty segments from old C* versions and unit tests {code} which I suspect is obsolete although I'm not sure what the effect on tests is. > Multithreaded commitlog > ----------------------- > > Key: CASSANDRA-3578 > URL: https://issues.apache.org/jira/browse/CASSANDRA-3578 > Project: Cassandra > Issue Type: Improvement > Reporter: Jonathan Ellis > Assignee: Benedict > Priority: Minor > Labels: performance > Attachments: 0001-CASSANDRA-3578.patch, ComitlogStress.java, > Current-CL.png, Multi-Threded-CL.png, TestEA.java, latency.svg, oprate.svg, > parallel_commit_log_2.patch > > > Brian Aker pointed out a while ago that allowing multiple threads to modify > the commitlog simultaneously (reserving space for each with a CAS first, the > way we do in the SlabAllocator.Region.allocate) can improve performance, > since you're not bottlenecking on a single thread to do all the copying and > CRC computation. > Now that we use mmap'd CommitLog segments (CASSANDRA-3411) this becomes > doable. > (moved from CASSANDRA-622, which was getting a bit muddled.) -- This message was sent by Atlassian JIRA (v6.1#6144)