unexpected full gc time spike

[the.6th.month at gmail.com]

hi, Ramki:
btw, could you possibly explain what the bugs are and how those bugs affect
the fallback fullgc time? I am really curious about the reason.
thanks very much.

all the best,
Leon
 On 17 May 2013 12:39, "the.6th.month at gmail.com" <the.6th.month at gmail.com>
wrote:

> thanks very much indeed, hope we can see your patch soon
>
>
> On 17 May 2013 12:38, Srinivas Ramakrishna <ysr1729 at gmail.com> wrote:
>
>> Hi Leon --
>>
>> Yes, there are a couple of performance bugs related to promotion
>> failure handling with ParNew+CMS that can cause this time to balloon.
>> Here the unwind of the failed promotion took 177 s. I have at least a
>> partial fix for this which I had written up a few months ago but never
>> quite got around to collecting sufficient performance data to submit
>> it as an official patch.
>>
>> I'll try and revive that patch and submit it... May be someone else
>> can check if it helps sufficiently in the performance with promotion
>> failure.
>>
>> -- ramki
>>
>>
>> On Thu, May 16, 2013 at 9:19 PM, the.6th.month at gmail.com
>> <the.6th.month at gmail.com> wrote:
>> > hi, all:
>> > We just had a situation that I don't quite understand with CMS gc. When
>> I
>> > examined the gc log, I found that there was a cms gc which resulted in a
>> > parnew promotion failure and concurrent mode failure at the same time,
>> and
>> > then the full gc lasted for slightly over three minutes. Here is the gc
>> log:
>> > 2013-05-17T10:12:55.983+0800: 45168.774: [CMS-concurrent-mark:
>> 7.056/7.860
>> > secs] [Times: user=14.90 sys=0.45, real=7.86 secs]
>> > 2013-05-17T10:12:55.984+0800: 45168.775: [CMS-concurrent-preclean-start]
>> > 2013-05-17T10:12:56.753+0800: 45169.544: [CMS-concurrent-preclean:
>> > 0.676/0.770 secs] [Times: user=0.83 sys=0.15, real=0.77 secs]
>> > 2013-05-17T10:12:56.753+0800: 45169.544:
>> > [CMS-concurrent-abortable-preclean-start]
>> > 2013-05-17T10:12:58.460+0800: 45171.251: [GC 45171.252: [ParNew
>> (promotion
>> > failed)
>> > Desired survivor size 67108864 bytes, new threshold 1 (max 6)
>> > - age   1:   70527216 bytes,   70527216 total
>> > : 917504K->917504K(917504K), 177.3558880 secs]45348.608: [CMS CMS: abort
>> > preclean due to time 2013-05-17T10:15:56.197+0800: 45348.989:
>> > [CMS-concurrent-abortable-preclean: 2.037/179.444 secs] [Times:
>> user=44.72
>> > sys=13.59, real=179.45 secs]
>> >  (concurrent mode failure): 3017323K->2177093K(3047424K), 16.5528620
>> secs]
>> > 3879476K->2177093K(3964928K), [CMS Perm : 91333K->91008K(262144K)],
>> > 193.9097970 secs] [Times: user=58.79 sys=13.55, real=193.91 secs]
>> >
>> > the usual cms full gc time was roughly 100ms-400ms, but this time it
>> lasted
>> > for 193 seconds. I understand that when there's a parnew gc happens
>> during
>> > cms and to space is not large enough to hold all survived objects, or
>> the
>> > remaining space in old gen cannot cope with memory allocation in old
>> gen,
>> > full gc happens. But I don't understand why it hangs so long.
>> > I am using oracle jdk 1.6.0_37, and the jvm options we use are:
>> > -Xms4000m -Xmx4000m -Xmn1G -Xss256k -XX:PermSize=256m
>> -XX:SurvivorRatio=6
>> > -XX:MaxTenuringThreshold=6 -XX:+DisableExplicitGC -Xnoclassgc
>> -Xverify:none
>> > -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -XX:+CMSParallelRemarkEnabled
>> > -XX:+UseCMSCompactAtFullCollection -XX:+UseFastAccessorMethods
>> > -XX:+CMSPermGenSweepingEnabled -XX:+CMSClassUnloadingEnabled
>> > -XX:+UseCompressedOops -XX:CMSInitiatingOccupancyFraction=90
>> > -XX:+UseCMSInitiatingOccupancyOnly
>> >
>> > Could it be a bug that results in the long full gc in case of promotion
>> > failure or something else? Could anyone offer me some help, and I really
>> > appreciate your help.
>> >
>> > Looking forward to any reply.
>> >
>> > All the best,
>> > Leon
>> >
>> >
>> > _______________________________________________
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>> > hotspot-gc-use at openjdk.java.net
>> > http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use
>> >
>>
>
>
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