PrintGCDate/TimeStamps

[Krystal Mok]

Hi Bernd,

You're probably using those two flags along with -Xloggc:filename. This
flag implies -XX:+PrintGCTimeStamps, which in your case is something you're
trying to get rid of.

There's an easy workaround to this: put -XX:-PrintGCTimeStamps *after*
-Xloggc.

The way HotSpot VM's argument processing works, if a VM flag is specified
multiple times, then the one that comes last is the one used. This includes
flags that are set implicitly.

There are different types of VM flags. "manageable" flags are ones that can
be changed at runtime, via the HotSpotDiagnostic MBean. PrintGCTimeStamps
is a manageable flag.

HTH,
Kris

On Wed, Aug 22, 2012 at 4:24 AM, Bernd Eckenfels <
bernd.eckenfels at googlemail.com> wrote:

> Hello,
>
> I wondering about some strange behaviour. Sorry to bother with this minor
> observation, but I do hope the datestamp ioption gets more popular by
> mention it again .)
>
> Often +PrintGCTimeStamps is recommended to be able to see the intervall
> between GC events. However I found some places talking about
> +PrintGCDateStamps which is much more convenient for some problems (for
> example correlating SLA violations with the STW pause times).
>
> Some discusions suggest that you can combine both in a way that it does
> not print both timestamps:
>
> -XX:+PrintGCDateStamps -XX:-PrintGCTimeStamps
>
> However on the win 64bit JDKs 1.6.0_33 and 1.7.0_03 I have tried this, it
> does not work (i.e. the logfiles always contans both, actually the
> timestamp typically 2 times):
>
> 2012-08-21T22:08:29.989+0200: 1.292: [GC 1.292: [ParNew:
> 5033216K->3826K(5662336K), 0.0015120 secs] 5033216K->3826K(6710912K),
> 0.0015790 secs] [Times: user=0.00 sys=0.00, real=0.00 secs]
> Total time for which application threads were stopped: 0.0018006 seconds
> 2012-08-21T22:08:30.605+0200: 1.907: [GC 1.907: [ParNew:
> 5037042K->5230K(5662336K), 0.0023563 secs] 5037042K->5230K(6710912K),
> 0.0024133 secs] [Times: user=0.00 sys=0.00, real=0.00 secs]
> Total time for which application threads were stopped: 0.0026457 seconds
>
> Just some additional information: I was able to tuen off the timestamps in
> the HotSpotDiagnostics MBean:
>
> 2012-08-21T22:19:54.858+0200: [GC [ParNew: 5039624K->5836K(5662336K),
> 0.0030131 secs] 5349974K->316537K(6710912K), 0.0030753 secs] [Times:
> user=0.00 sys=0.00, real=0.00 secs]
>
> Greetings
> Bernd
>
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