Long ParNew Collection Time

[Y. S. Ramakrishna]

I'd do all of this after following Chi-Ho's suggestions
on swappiness settings, of course. Also, -XX:+AlwaysPreTouch
to touch all of the heap pages up front, just in case this is an artifact
of touching the occasional new page(s) for the first time in the
life of the process and hitting a Linux virtual memory pothole.
But this is all conjecture of course...

-- ramki

On 01/11/11 08:48, Y. S. Ramakrishna wrote:
> 
> 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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>>
>