hbase-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-13082) Coarsen StoreScanner locks to RegionScanner
Date Sun, 22 Feb 2015 00:50:11 GMT

     [ https://issues.apache.org/jira/browse/HBASE-13082?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Lars Hofhansl updated HBASE-13082:
----------------------------------
    Attachment: 13082.txt

Simple patch. (much like the patch on HBASE-10015).

A bit ugly, because I did not want to change the coprocessor APIs.

Also thought of another drawback:
* Nobody (coprocessor) can use StoreScanner alone anymore (there'd be nothing to lock), i.e.
all access *must* be via Rigi.onScannerImpl or flushes or compactions). I think that's OK.

Maybe we can make the lock the compactions/flushes and StoreScanner have to agree upon explicit.


> Coarsen StoreScanner locks to RegionScanner
> -------------------------------------------
>
>                 Key: HBASE-13082
>                 URL: https://issues.apache.org/jira/browse/HBASE-13082
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>         Attachments: 13082.txt
>
>
> Continuing where HBASE-10015 left of.
> We can avoid locking (and memory fencing) inside StoreScanner by deferring to the lock
already held by the RegionScanner.
> In tests this shows quite a scan improvement and reduced CPU (the fences make the cores
wait for memory fetches).
> There are some drawbacks too:
> * All calls to RegionScanner need to be remain synchronized
> * Implementors of coprocessors need to be diligent in following the locking contract.
For example Phoenix does not lock RegionScanner.nextRaw() and required in the documentation
(not picking on Phoenix, this one is my fault as I told them it's OK)
> * possible starving of flushes and compaction with heavy read load. RegionScanner operations
would keep getting the locks and the flushes/compactions would not be able finalize the set
of files.
> I'll have a patch soon.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

Mime
View raw message