RFR (S): 7176220 'Full GC' events miss date stamp information occasionally

Andreas Eriksson andreas.eriksson at oracle.com
Tue May 14 09:21:41 UTC 2013


Hi,

I changed the date and time stamping calls to use the guarded 
convenience variants.
Both of these calls suffixes a ": " automatically. See 
share/vm/utilities/ostream.hpp line 99 and 105.

It currently looks like this:
% ./hsx24_hotspot-build/bin/java -Xmx2m -verbose:gc 
-XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps HumongousAlloc
2013-05-14T11:17:28.340+0200: 0.050: [GC 1896K->421K(3136K), 0.0011640 secs]
2013-05-14T11:17:28.341+0200: 0.051: [GC 2329K->437K(3136K), 0.0029750 secs]

This is how it looked before as well:
% ~/builds/linux-amd64/7u25/bin/java -Xmx2m -verbose:gc 
-XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps HumongousAlloc
2013-05-14T11:17:31.603+0200: 0.059: [GC 2025K->417K(3136K), 0.0008100 secs]
2013-05-14T11:17:31.605+0200: 0.060: [GC 2325K->417K(3136K), 0.0015140 secs]

Thanks for looking at this.

/Andreas

On 2013-05-14 08:23, Bengt Rutisson wrote:
>
> Hi Andreas,
>
> Looks good.
>
> One question regarding the change in GCTraceTime:
>
> http://cr.openjdk.java.net/~aeriksso/7176220/webrev.00/src/share/vm/gc_implementation/shared/gcTraceTime.cpp.udiff.html
>
> It looks to me like we are missing a ": " in the new version. Maybe it 
> is ok to loose this character in the log format, but a safer change 
> may be:
>
> if (PrintGCTimeStamps || PrintGCDateStamps) {
>   gclog_or_tty->date_stamp(PrintGCDateStamps);
>   gclog_or_tty->stamp(PrintGCTimeStamps);
> gclog_or_tty->print(": ");
> }
>
> This actually still changes the ": " behavior since since you didn't 
> use to get a ": " if you only had PrintGCDateStamps enabled. But I 
> think this is a more expected behavior.
>
> Thanks,
> Bengt
>
> On 5/13/13 6:01 PM, Andreas Eriksson wrote:
>> Hi all,
>>
>> Please take a look at my changes for bug 7176220.
>> The problem is that CMS sometimes misses datestamps for time trace 
>> printouts.
>>
>> The proposed fix is to move the datestamp print logic into the class 
>> that handles time trace printouts, GCTraceTime.
>> This would make it consistent with timestamps, which are already 
>> printed from there.
>>
>> Bugs.sun:
>> http://bugs.sun.com/view_bug.do?bug_id=7176220
>>
>> JIRA:
>> https://jbs.oracle.com/bugs/browse/JDK-7176220
>>
>> Webrev:
>> http://cr.openjdk.java.net/~aeriksso/7176220/webrev.00/
>>
>> Testing:
>> jprt, jtreg
>>
>> Thanks,
>> Andreas
>>
>

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