Continuous CMS Collections Followed By Concurrent Mode Failure

Srinivas Ramakrishna ysr1729 at gmail.com
Tue Jul 15 07:29:15 UTC 2014


If it were fragmentation only, then one wouldn't see free memory increase
that dramatically after the compaction. All that the compaction should do
is compact the objects while leaving free space in roughly the same ball
park as before. Not the huge reduction from used memory of 1.92 GB to 50.7
MB. (Again, I am just reading yr email not paying attention to the logs.)

I'd suggest turning on class unloading and see how far you are able to get.
Fragmentation might still get you, but the signal in that case would be
clearer. Also, I think CMS has an option
that prints the cause of a collection and similarly for a concurrent mode
failure (IIRC).
-- ramki


On Mon, Jul 14, 2014 at 6:31 PM, Elliot Barlas <Elliot.Barlas at citrix.com>
wrote:

>  Alternatively, could my problem be due to fragmentation?  Are there
> segments of free address space that are too small to use that could
> eventually be responsible for exhausting the old generation?
>
>  -Elliot
>
>  ------------------------------
> *From:* Kirk Pepperdine [kirk at kodewerk.com]
> *Sent:* Wednesday, July 09, 2014 1:24 AM
>
> *To:* Srinivas Ramakrishna
> *Cc:* Elliot Barlas; hotspot-gc-dev at openjdk.java.net openjdk.java.net
> *Subject:* Re: Continuous CMS Collections Followed By Concurrent Mode
> Failure
>
>  Hi Ramki,
>
>  No need for flame proof suites… The (promotion failed) has been
> separated from the ParNew. I can easily adjust for this change… it’s just
> one more in a line of 100s of trivial changes that don’t add value to the
> GC logs… <sighs> ;-)
>
>  — Kirk
>
>  On Jul 9, 2014, at 3:45 AM, Srinivas Ramakrishna <ysr1729 at gmail.com>
> wrote:
>
>
> On Tue, Jul 8, 2014 at 12:06 AM, Kirk Pepperdine <kirk at kodewerk.com>
> wrote:
>
>>  ...
>> Ramki, should we file a bug for the ParNew (promotion failed) being
>> corrupted by a CMS cycle?
>>
>>
>  Can you elaborate what precisely you meant by "corrupted (formatting)"
> below?
>
>  Perhaps you want what seems to be a missing newline or something? You
> should check with Jon or one of the HotSpot/GC folks on whether and how
> easy it would be to fix, or otherwise modify your parser. (Kevlar suit
> donned, for yr response ;-)
>
>  -- ramki
>
>>
>>  That was actually my guess. There is only 1 perm record in the file and
>> although it shows that perm is grossly over-sized (ok, there is only one
>> record ;-)) all of the recovery comes from the CMF which suggests perm is
>> involved. All of the other CMS cycles are clearly due to tenured never
>> being below the initiating occupancy fraction. Even without a young
>> collection the initial marks are constantly reporting an occupancy of
>> >1920xxxK of 1929xxxK. Oddly enough the ParNew’s only once promoted enough
>> to trip the concurrent mode failure and oddly enough each of the CMS cycles
>> (without the intervening ParNew) seem to recover about 1xxK bytes per cycle.
>>
>>  2014-06-10T22:56:18.793-0700: 4999527.565: [GC [1 CMS-initial-mark:
>> 1920286K(1926784K)] 2051254K(2080128K), 0.3388330 secs] [Times: user=0.33
>> sys=0.00, real=0.33 secs]
>> …...
>> 2014-06-10T22:56:26.242-0700: 4999535.014:
>> [GC2014-06-10T22:56:26.242-0700: 4999535.014:
>> [ParNew2014-06-10T22:56:26.256-0700: 4999535.028:
>> [CMS-concurrent-abortable-preclean: 1.948/3.114 secs] [Times: user=1.93
>> sys=0.12, real=3.11 secs]
>>  (promotion failed)
>> Desired survivor size 8716288 bytes, new threshold 6 (max 6)
>> - age   1:    1036320 bytes,    1036320 total
>> - age   2:     825248 bytes,    1861568 total
>> - age   3:     119024 bytes,    1980592 total
>> - age   4:     113784 bytes,    2094376 total
>> - age   5:     129024 bytes,    2223400 total
>> - age   6:     154976 bytes,    2378376 total
>> : 141769K->140729K(153344K), 0.3807730 secs]2014-06-10T22:56:26.623-0700:
>> 4999535.395: [CMS
>>  (concurrent mode failure): 1920816K->50773K(1926784K), 28.3938140 secs]
>> 2062055K->50773K(2080128K), [CMS Perm : 48657K->41071K(262144K)],
>> 28.7750370 secs] [Times: user=1.65 sys=0.03, real=28.78 secs]
>>  2014-06-10T22:58:41.361-0700: 4999670.133:
>> [GC2014-06-10T22:58:41.361-0700: 4999670.133: [ParNew
>> Desired survivor size 8716288 bytes, new threshold 6 (max 6)
>> - age   1:    1239232 bytes,    1239232 total
>> : 136320K->2239K(153344K), 0.0223680 secs] 187093K->53012K(2080128K),
>> 0.0226340 secs] [Times: user=0.05 sys=0.00, real=0.02 secs]
>>
>>  Note the corrupted formatting of the ParNew (promotion failed).
>>
>>
>
>
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