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From "Peter Schuller (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-1827) Batching across stages
Date Thu, 11 Aug 2011 16:25:27 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1827?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13083206#comment-13083206
] 

Peter Schuller commented on CASSANDRA-1827:
-------------------------------------------

The following is speculation and should not be construed as a strong claim ;)

I don't have proof but I suspect that putting/popping individual entries is fairly significant,
mostly because of the context switching involved and interaction with the scheduler. Empirically
when stress-testing it seems to me that under CPU bound workloads the stages are often not
saturated (and you certainly don't saturate all cores despite high concurrency). In other
words, even with a consistent backlog of pending tasks the active tasks aren't consistently
at full concurrency. I wonder what kind of effects come form delay in waking up a thread.

Something similar to consider might be to try to use a non-blocking queue (you'd still presumably
block in low-throughput cases, but have the potential to proceed lock-lessly under high load).

> Batching across stages
> ----------------------
>
>                 Key: CASSANDRA-1827
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1827
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Chris Goffinet
>             Fix For: 1.0
>
>
> We might be able to get some improvement if we start batching tasks for every stage.

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