Extremely long parnew/cms promotion failure scenario?

[Srinivas Ramakrishna]

Has anyone come across extremely long (upwards of 10 minutes) promotion
failure unwinding scenarios when using any of the collectors, but
especially with ParNew/CMS?
I recently came across one such occurrence with ParNew/CMS that, with a 40
GB young gen took upwards of 10 minutes to "unwind". I looked through the
code and I can see
that the unwinding steps can be a source of slowdown as we iterate
single-threaded (DefNew) through the large Eden to fix up self-forwarded
objects, but that still wouldn't
seem to explain such a large pause, even with a 40 GB young gen. I am
looking through the promotion failure paths to see what might be the cause
of such a large pause,
but if anyone has experienced this kind of scenario before or has any
conjectures or insights, I'd appreciate it.

thanks!
-- ramki
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