[jira] [Commented] (CASSANDRA-3376) Track buffer cache hit rate with mincore

["Jonathan Ellis (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-3376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13801934#comment-13801934 ] 

Jonathan Ellis commented on CASSANDRA-3376:
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bq. we don't know how much of an sstable we'll need to read for a given slice ahead of time

Thinking about it more, just checking the position where we start the slice would probably be Good Enough (certainly better than nothing).

> Track buffer cache hit rate with mincore
> ----------------------------------------
>
>                 Key: CASSANDRA-3376
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3376
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Jonathan Ellis
>            Priority: Minor
>              Labels: ponies
>
> We could use mincore on, say, 1% of reads to be able to report actual buffer cache hit rate.  This would be useful when troubleshooting slow reads, e.g., are reads to CF X slow because it's hitting disk, or because there are a lot of tombstones in the row?



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