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From "Zee Chen (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-13259) mmap() based BucketCache IOEngine
Date Tue, 17 Mar 2015 01:26:39 GMT

     [ https://issues.apache.org/jira/browse/HBASE-13259?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Zee Chen updated HBASE-13259:
-----------------------------
    Attachment: mmap-0.98-v1.patch

> mmap() based BucketCache IOEngine
> ---------------------------------
>
>                 Key: HBASE-13259
>                 URL: https://issues.apache.org/jira/browse/HBASE-13259
>             Project: HBase
>          Issue Type: New Feature
>          Components: BlockCache
>    Affects Versions: 0.98.10
>            Reporter: Zee Chen
>         Attachments: mmap-0.98-v1.patch
>
>
> Of the existing BucketCache IOEngines, FileIOEngine uses pread() to
> copy data from kernel space to user space. This is a good choice when the
> total working set size is much bigger than the available RAM and the latency is dominated
by IO access. However, when the entire working set is
> small enough to fit in the RAM, using mmap() (and subsequent memcpy()) to move data from
kernel space to user space is faster. I have run some short keyval gets tests and the results
indicate a reduction of 2%-7% of kernel CPU on my system, depending on the load. On the gets,
the latency
> histograms from mmap() are identical to those from pread(), but peak
> throughput is close to 40% higher.
> This patch modifies ByteByfferArray to allow it to specify a backing file.
> Example for using this feature: set  hbase.bucketcache.ioengine to mmap:/dev/shm/bucketcache.0
in hbase-site.xml.



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