starts with the easiest/fastest to find and then sees what more it
>>> > thinks it needs to do to create enough memory for anticipated near
>>> > future needs.
>>> >
>>> > On Thu, May 26, 2011 at 10:16 PM, Jonathan Ellis
>>> >
rately done
>> >> something like setting the -XX:-DisableExplicitGC flag.
>> >>
>> >> On Thu, May 26, 2011 at 5:58 PM, Konstantin Naryshkin
>> >> wrote:
>> >>> So, in summary, there is no way to predictably and efficiently tell
>>
> >> wrote:
> >>> So, in summary, there is no way to predictably and efficiently tell
> Cassandra to get rid of all of the extra space it is using on disk?
> >>>
> >>> - Original Message -
> >>> From: "Jeffrey Kesselman"
> Even if the gc call cleaned all files, it is not really acceptable on a
> decent sized cluster due to the impact full gc has on performance.
> Especially non-needed ones.
You can run with -XX:+ExplicitGCInvokesConcurrent to "safely" trigger
CMS cycles. However that also means System.gc() semanti
There's a ticket open to address this:
https://issues.apache.org/jira/browse/CASSANDRA-1974
-ryan
On Wed, Jun 15, 2011 at 8:49 AM, Terje Marthinussen
wrote:
>
>
> On Thu, Jun 16, 2011 at 12:48 AM, Terje Marthinussen
> wrote:
>>
>> Even if the gc call cleaned all files, it is not really accepta
tell Cassandra to get rid of all of the extra space it is using on
disk?
>>>
>>> - Original Message -
>>> From: "Jeffrey Kesselman" mailto:jef...@gmail.com>>
>>> To: user@cassandra.apache.org <mailto:user@cassand
On Thu, Jun 16, 2011 at 12:48 AM, Terje Marthinussen <
tmarthinus...@gmail.com> wrote:
> Even if the gc call cleaned all files, it is not really acceptable on a
> decent sized cluster due to the impact full gc has on performance.
> Especially non-needed ones.
>
>
Not acceptable as running GC on ev
aryshkin
> >> wrote:
> >>> So, in summary, there is no way to predictably and efficiently tell
> Cassandra to get rid of all of the extra space it is using on disk?
> >>>
> >>> - Original Message -
> >>> From: "Jeffrey Kesselman"
--- Original Message -
>>> From: "Jeffrey Kesselman"
>>> To: user@cassandra.apache.org
>>> Sent: Thursday, May 26, 2011 8:57:49 PM
>>> Subject: Re: Forcing Cassandra to free up some space
>>>
>>> Which JVM? Which collector? Ther
For the purposes of clearing out disk space, you might also occasionally check
to see if you have snapshots that you no longer need. Certain operations
create snapshots (point-in-time backups of sstables) in the (default)
/var/lib/cassandra/data//snapshots directory.
If you are absolutely sure
--
>> From: "Jeffrey Kesselman"
>> To: user@cassandra.apache.org
>> Sent: Thursday, May 26, 2011 8:57:49 PM
>> Subject: Re: Forcing Cassandra to free up some space
>>
>> Which JVM? Which collector? There have been and continue to be many.
>>
&g
sing on disk?
>>
>> - Original Message -
>> From: "Jeffrey Kesselman"
>> To: user@cassandra.apache.org
>> Sent: Thursday, May 26, 2011 8:57:49 PM
>> Subject: Re: Forcing Cassandra to free up some space
>>
>> Which JVM? Which coll
f the extra space it is using on disk?
>
> - Original Message -
> From: "Jeffrey Kesselman"
> To: user@cassandra.apache.org
> Sent: Thursday, May 26, 2011 8:57:49 PM
> Subject: Re: Forcing Cassandra to free up some space
>
> Which JVM? Which collec
"Is there a way for me to make (or even gently suggest to) Cassandra that it
may be a good time to free up some space?"
Disregarding what's been said and until ref-counting is implemented this is
a useful tool to gently suggest cleanup:
https://github.com/ceocoder/jmxgc
On Thu, May 26, 2011 at
to get rid of all of the extra space it is using on disk?
>
> - Original Message -
> From: "Jeffrey Kesselman"
> To: user@cassandra.apache.org
> Sent: Thursday, May 26, 2011 8:57:49 PM
> Subject: Re: Forcing Cassandra to free up some space
>
> Which JVM
ssandra to free up some space
Which JVM? Which collector? There have been and continue to be many.
Hotspot itself supports a number of different collectors with
different behaviors. Many of them do not collect every candidate on
every gc, but merely the easiest ones to find. This is why de
Which JVM? Which collector? There have been and continue to be many.
Hotspot itself supports a number of different collectors with
different behaviors. Many of them do not collect every candidate on
every gc, but merely the easiest ones to find. This is why depending
on finalizers is a *bad*
I've read the relevant source. While you're pedantically correct re
the spec, you're wrong as to what the JVM actually does.
On Thu, May 26, 2011 at 3:14 PM, Jeffrey Kesselman wrote:
> Some references...
>
> "An object enters an unreachable state when no more strong references
> to it exist. When
Some references...
"An object enters an unreachable state when no more strong references
to it exist. When an object is unreachable, it is a candidate for
collection. Note the wording: Just because an object is a candidate
for collection doesn't mean it will be immediately collected. The JVM
is fr
Im sorry. This was my business at Sun. You are certainly wrong about
the Hotspot VM.
See this chapter of my book
http://java.sun.com/docs/books/performance/1st_edition/html/JPAppGC.fm.html#998394
On Thu, May 26, 2011 at 3:53 PM, Jonathan Ellis wrote:
> It's a common misunderstanding that
It's a common misunderstanding that system.gc is only a suggestion; on
any VM you're likely to run Cassandra on, System.gc will actually
invoke a full collection.
On Thu, May 26, 2011 at 2:18 PM, Jeffrey Kesselman wrote:
> Actually this is no gaurantee. Its a common misunderstanding that
> Syst
Actually this is no gaurantee. Its a common misunderstanding that
System.gc "forces" gc. It does not. It is a suggestion only. The vm always
has the option as to when and how much it gcs
On May 26, 2011 2:51 PM, "Jonathan Ellis" wrote:
You'd have to call system.gc via JMX.
https://issues.apache.org/jira/browse/CASSANDRA-2521 is open to
address this, btw.
On Thu, May 26, 2011 at 1:09 PM, Konstantin Naryshkin
wrote:
> I have a basic understanding of how Cassandra handles the file system
> (flushes in Memtables out to SSTables,
I have a basic understanding of how Cassandra handles the file system (flushes
in Memtables out to SSTables, SSTables get compacted) and I understand that old
files are only deleted when a node is restarted, when Java does a GC, or when
Cassandra feels like it is running out of space.
My quest
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