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Posted to dev@hbase.apache.org by "ryan rawson (JIRA)" <ji...@apache.org> on 2010/02/02 23:14:18 UTC
[jira] Assigned: (HBASE-2180) read performance from synchronizing
hfile.fddatainputstream
[ https://issues.apache.org/jira/browse/HBASE-2180?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
ryan rawson reassigned HBASE-2180:
----------------------------------
Assignee: ryan rawson
> read performance from synchronizing hfile.fddatainputstream
> -----------------------------------------------------------
>
> Key: HBASE-2180
> URL: https://issues.apache.org/jira/browse/HBASE-2180
> Project: Hadoop HBase
> Issue Type: Bug
> Reporter: ryan rawson
> Assignee: ryan rawson
> Fix For: 0.21.0
>
>
> deep in the HFile read path, there is this code:
> synchronized (in) {
> in.seek(pos);
> ret = in.read(b, off, n);
> }
> this makes it so that only 1 read per file per thread is active. this prevents the OS and hardware from being able to do IO scheduling by optimizing lots of concurrent reads.
> We need to either use a reentrant API (pread may be partially reentrant according to Todd) or use multiple stream objects, 1 per scanner/thread.
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