CMS collection keep working during holiday

[Y Srinivas Ramakrishna]

Let me see if i understood that:-

> What the application is simply a stock quote client server and store daily
> stock quote and chart data in memory. The lived objects need around 80M
> memory at day open and 500M memory at day end.

So you expect that the long-lived objects that will eventually get
promoted into the old generation, will start out at about 80 MB
at the start of the trading day and will end up about 500 MB at the
end of the trading day.

What happens at the end of the trading day? Do you discard the entire
table, so that the set of long-lived objects would be expected to shrink
back to 80 MB after the trading day ends?

If I understood your problem correctly (and correct me if i am wrong)
you find that the old gen occupancy does not shrink down with
concurrent collections at the end of the trading day, but shrinks only
upon a mark-compact collection (which typically happens as a result of
a promotion failure).

(Loud thinking: I am assuming that the same effect would be achieved
by calling a System.gc() at the end of the trading day after the
table of quotes has been dropped. Of course, we need to figure out
why CMS may not reclaim the table even though it has been dropped.]

Please correct any misunderstanding of the situation.
-- ramki
 
> 
> y.s.ramakrishna wrote:
> > 
> > 
> > Could you run with the additional option +PrintReferenceGC and see if
> > it sheds additional light on the problem? (Please share the resulting
> > GC logs.)
> > 
> > If at all possible, you might try rev'ing down to 6.0 and seeing
> > if the same behaviour reproduces or not?
> > 
> > I understand that some or all of this may not be possible in a
> > production setting.
> > 
> > -- ramki
> > 
> > ----- Original Message -----
> > From: "Ken-- at newsgroupstats.hk" <dragonken at gmail.com>
> > Date: Tuesday, October 7, 2008 10:17 pm
> > Subject: Re: CMS collection keep working during holiday
> > To: hotspot-gc-dev at openjdk.java.net
> > 
> > 
> >> Follow up to the jconsole above. This gif is captured today. You 
> can 
> >> see the
> >> first CMS after a FULL GC is working. The 2nd one is working too 
> but the
> >> memory free from 2nd generation is much less than the first CMS. The
> >> memory
> >> free by 3rd CMS is further decreased.
> >> 
> >> The 5th CMS cannot free enough memory to make occanpcy in old-gen 
> to less
> >> than 70%. So, continue non-stopping CMS happen again until a Full GC
> >> (triggered by Concurrent Mode Failure).
> >> 
> >> http://www.nabble.com/file/p19872463/jconsole_20081008.jpg 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
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> archive 
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> >> 
> > 
> > 
> 
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