cassandra-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Jonathan Ellis (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-5863) In process (uncompressed) page cache
Date Sat, 01 Nov 2014 01:24:34 GMT


Jonathan Ellis commented on CASSANDRA-5863:

bq. The Tricky part is tracking the "hotness" of these chunks. It needs to track the number
of times the chunk was decompressed in the last X seconds. 

Backing up a bit -- why not just take a LRU approach?  When we uncompress a chunk, we cache
it.  Add metrics so users can monitor cache churn and disable if it's not useful.  (But since
our chunks are fairly large, and thus decompressing is relatively expensive, I think we could
tolerate relatively high churn.)

> In process (uncompressed) page cache
> ------------------------------------
>                 Key: CASSANDRA-5863
>                 URL:
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: T Jake Luciani
>              Labels: performance
>             Fix For: 3.0
> Currently, for every read, the CRAR reads each compressed chunk into a byte[], sends
it to ICompressor, gets back another byte[] and verifies a checksum.  
> This process is where the majority of time is spent in a read request.  
> Before compression, we would have zero-copy of data and could respond directly from the
> It would be useful to have some kind of Chunk cache that could speed up this process
for hot data, possibly off heap.

This message was sent by Atlassian JIRA

View raw message