Long young generation GC?

Y. Srinivas Ramakrishna y.s.ramakrishna at oracle.com
Mon Oct 25 17:51:57 PDT 2010


On 10/25/2010 5:49 PM, Y. Srinivas Ramakrishna wrote:
> On 10/25/2010 5:32 PM, Hi Guava wrote:
>> The third young generation GC took 439.2720750 secs but the user and
>> real time are only 0.08 seconds. What does it mean?
>
> The machine may be using NTP, and the time may have been changed?

Seems a rather large jump, so may not be NTP (which i am told uses
adjtime() to slowly accelerate the time forward or decelerate it backward),
but rather an abrupt perhaps manual change in TOD.

Over to the experts....

> JVM timestamps on Linux seem still to be based on TOD rather than
> on TSC. Someone in the runtime team (cc'd) may have more detail on
> why that might still be so.
>
> -- ramki
>
>
>>
>> 72667.213: [GC 72667.213: [ParNew: 38336K->4224K(38336K), 1.2473840 secs]
>> 3443948K->3420569K(6549376K), 1.2474290 secs] [Times: user=0.64 sys=1.10,
>> real=1.25 secs]
>> 72680.531: [GC 72680.532: [ParNew: 38336K->4221K(38336K), 0.2916570 secs]
>> 3008948K->2979033K(6549376K), 0.2916710 secs] [Times: user=0.26 sys=0.03,
>> real=0.29 secs]
>> 72681.425: [GC 72681.426: [ParNew: 38325K->4224K(38336K), 439.2720750
>> secs] 3013053K->2979055K(6549376K), 439.2720750 secs] [Times: user=0.08
>> sys=0.00, real=0.08 secs]
>>
>> Environment:
>> Java HotSpot(TM) 64-Bit Server VM Version 1.6.0_20-b02
>> Linux Version 2.6.18-128.1.1.el5 on amd64
>> -Xms6400m
>> -Xmx6400m
>> -Xss256k
>> -XX:+UseConcMarkSweepGC
>> -XX:+PrintGCDetails
>> -XX:+PrintGCTimeStamps
>> -XX:+UseCompressedOops
>> _______________________________________________
>> hotspot-gc-use mailing list
>> hotspot-gc-use at openjdk.java.net
>> http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use
>

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