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Date: Tue, 25 Jan 2011 16:17:46 -0500 (EST)
From: "Javier Canillas (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Subject: [jira] Commented: (CASSANDRA-1379) Uncached row reads may block
 cached reads
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    [ https://issues.apache.org/jira/browse/CASSANDRA-1379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12986686#action_12986686 ] 

Javier Canillas commented on CASSANDRA-1379:
--------------------------------------------

Actually, on the patch both reads times will impact on the only read counter. Maybe creating a separate counter for cache reads and physical reads would be good. On the other hand, i dont remember if there is a miss counter over cache, if there is, it would be surely impacted

> Uncached row reads may block cached reads
> -----------------------------------------
>
>                 Key: CASSANDRA-1379
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1379
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: David King
>            Assignee: Javier Canillas
>            Priority: Minor
>             Fix For: 0.7.2
>
>         Attachments: CASSANDRA-1379.patch
>
>
> The cap on the number of concurrent reads appears to cap the *total* number of concurrent reads instead of just capping the reads that are bound for disk. That is, given N concurrent readers if all of them are busy waiting on disk, even reads that can be served from the row cache will block waiting for them.

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