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From lars hofhansl <lhofha...@yahoo.com>
Subject Re: FeedbackRe: Suspected memory leak
Date Sun, 04 Dec 2011 20:24:00 GMT
Thanks. Now the question is: How many connection threads do we have?

I think there is one per regionserver, which would indeed be a problem.
Need to look at the code again (I'm only partially familiar with the client code).

Either the client should chunk (like the server does), or there should be a limited number
of thread that
perform IO on behalf of the client (or both).

-- Lars

----- Original Message -----
From: Gaojinchao <gaojinchao@huawei.com>
To: "dev@hbase.apache.org" <dev@hbase.apache.org>; lars hofhansl <lhofhansl@yahoo.com>
Cc: Chenjian <jean.chenjian@huawei.com>; wenzaohua <wenzaohua@huawei.com>
Sent: Saturday, December 3, 2011 11:22 PM
Subject: Re: FeedbackRe: Suspected memory leak

This is dump stack.

发件人: lars hofhansl [mailto:lhofhansl@yahoo.com] 
发送时间: 2011年12月4日 14:15
收件人: dev@hbase.apache.org
抄送: Chenjian; wenzaohua
主题: Re: FeedbackRe: Suspected memory leak

Dropping user list.

Could you (or somebody) point me to where the client is using NIO?
I'm looking at HBaseClient and I do not see references to NIO, also it seems that all work
is handed off to
separate threads: HBaseClient.Connection, and the JDK will not cache more than 3 direct buffers
per thread.

It's possible (likely?) that I missed something in the code.


-- Lars

From: Gaojinchao <gaojinchao@huawei.com>
To: "user@hbase.apache.org" <user@hbase.apache.org>; "dev@hbase.apache.org" <dev@hbase.apache.org>

Cc: Chenjian <jean.chenjian@huawei.com>; wenzaohua <wenzaohua@huawei.com> 
Sent: Saturday, December 3, 2011 7:57 PM
Subject: FeedbackRe: Suspected memory leak

Thank you for your help.

This issue appears to be a configuration problem:
1. HBase client uses NIO(socket) API that uses the direct memory.
2. Default -XXMaxDirectMemorySize value is equal to -Xmx value, So if there doesn't have "full
gc", all direct memory can't reclaim. Unfortunately, using GC confiugre parameter of our client
doesn't produce any "full gc".

This is only a preliminary result,  All tests is running, If have any further results , we
will be fed back.
Finally , I will update our story to issue https://issues.apache.org/jira/browse/HBASE-4633.

If our digging is crrect, whether we should set a default value for the "-XXMaxDirectMemorySize"
to prevent this situation?


发件人: bijieshan [mailto:bijieshan@huawei.com] 
发送时间: 2011年12月2日 15:37
收件人: dev@hbase.apache.org; user@hbase.apache.org
抄送: Chenjian; wenzaohua
主题: Re: Suspected memory leak

Thank you all. 
I think it's the same problem with the link provided by Stack. Because the heap-size is stabilized,
but the non-heap size keep growing. So I think not the problem of the CMS GC bug. 
And we have known the content of the problem memory section, all the records contains the
info like below:


发件人: Kihwal Lee [mailto:kihwal@yahoo-inc.com] 
发送时间: 2011年12月2日 4:20
收件人: dev@hbase.apache.org
抄送: Ramakrishna s vasudevan; user@hbase.apache.org
主题: Re: Suspected memory leak

Adding to the excellent write-up by Jonathan:
Since finalizer is involved, it takes two GC cycles to collect them.  Due to a bug/bugs in
the CMS GC, collection may not happen and the heap can grow really big.  See http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7112034
for details.

Koji tried "-XX:-CMSConcurrentMTEnabled" and confirmed that all the socket related objects
were being collected properly. This option forces the concurrent marker to be one thread.
This was for HDFS, but I think the same applies here.


On 12/1/11 1:26 PM, "Stack" <stack@duboce.net> wrote:

Make sure its not the issue that Jonathan Payne identifiied a while
back: https://groups.google.com/group/asynchbase/browse_thread/thread/c45bc7ba788b2357# 

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