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Jonathan Ellis commented on CASSANDRA-3578: ------------------------------------------- bq. I agree it's difficult to avoid talking about last when talking about next, but this is typical since it's chained. How about this? {code} // Everything before this offset has been synced and written. The SYNC_MARKER_SIZE bytes after // this offset are reserved, and point forwards to the next sync position. The final // sync marker in a segment will be zeroed out, or point to EOF. private volatile int lastSyncedOffset; {code} > 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)