[
https://issues.apache.org/jira/browse/CASSANDRA-3578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13834988#comment-13834988
]
Benedict commented on CASSANDRA-3578:
-------------------------------------
Was browsing your changes and noticed your CL.getContext() comment
clarification, which I think probably doesn't go far enough - also realised its
return value no longer needs to be a Future (the callee also only uses
immediateFuture). I think something like the following is appropriate:
{noformat}
/**
* @return a ReplayPosition representing the current position of the
commit log;
* any CL.add() that completed prior to this call will occur at an
earlier ReplayPosition.
* This makes no guarantees about persistence, only ordering
*/
public ReplayPosition getContext()
{
return allocator.allocatingFrom().getContext()
}
{noformat}
> 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, 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)
