Long ParNew Collection Time

[Y. S. Ramakrishna]

Hi Shay --

On 01/11/11 05:05, Shay Banon wrote:
> 
> I will give it a go. Are you suggesting that its just a time reporting 
> problem, and there is no actual long GC? It does correlate with the 
> system hanging and not doing anything during that time (not responding 
> to any requests from clients).

Yes, that was what I was suggesting, but from your description
it sounds like it's a "real" problem (pun intended). So we'll need to
see what's happening. Disabling NTP would be good anyway in order
to investigate further. If you already have the data, you might want
to lay the GC pause data, the client response time data and
the vmstat data in an (aligned) time series plot (or other) to see
if there's any correlation (rather than focusing on single events).

-- ramki

> 
> -shay.banon
> 
> On Tuesday, January 11, 2011 at 9:40 AM, Y. Srinivas Ramakrishna wrote:
> 
>> Is the system TOD being changed? May be an overzealous NTP daemon?
>> Can you make sure NTP is disabled and see if the problem goes away?
>>
>> -- ramki
>>
>>
>> On 1/10/2011 10:30 PM, Shay Banon wrote:
>>> Hi,
>>>
>>>
>>> Running a JVM (1.6u23) on ubuntu 10.0 (machine has 32gb) getting this 
>>> GC log output:
>>>
>>>
>>> 3856.471: [GC 3856.471: [ParNew: 118016K->13056K(118016K), 37.8958700 
>>> secs] 689035K->593566K(8375552K), 37.8959970 secs] [Times: user=0.00 
>>> sys=0.00, real=37.90 secs]
>>>
>>>
>>> As you can see, the it seems like time wise, its all real.
>>>
>>>
>>> Flags used are:
>>>
>>>
>>> -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -Xms8g -Xmx8g
>>>
>>>
>>> Tried also with:
>>>
>>>
>>> * -XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=1 
>>> -XX:CMSInitiatingOccupancyFraction=75
>>> * -XX:-CMSConcurrentMTEnabled
>>>
>>>
>>> Checked vmstat during the run, and don't see any swapping going on 
>>> (si/so are 0, no swap).
>>>
>>>
>>> Any idea on how to try and solve this?
>>>
>>>
>>> cheers,
>>> -shay.banon
>>>
>>>
>>>
>>>
>>>
>>>
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> 
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