Request for review - 7197557

Vitaly Davidovich vitalyd at
Wed Sep 19 23:07:46 UTC 2012

Hi Jon,

Do the Metaspace size args allow use of size specifiers (e.g. "g", "m",
etc) like Xmx/Xms? I don't have code in front of me but it's a bit unclear
from the option descriptions since they mention that the value is in bytes.


Sent from my phone
On Sep 19, 2012 6:31 PM, "Jon Masamitsu" <jon.masamitsu at> wrote:

> On 9/18/2012 12:04 PM, Srinivas Ramakrishna wrote:
>> ....
>> Great; thanks a lot for that information. I am assuming that in general
>> full gc's as a result of the Java heap
>> filling up will, in most cases, take care of reclaiming enough space in
>> the
>> metadata spaces, so that no explicit
>> collection is needed for the total size of the metadata spaces to stay
>> within the HWM computed. By the way, I assume that
> That's my experience.    GC's happen much more often because the heap gets
>  full
> and the GC's (full) unload classes.
>  there is some way that we can set the starting and maximum metaspace size
>> to the same value, analogous
>> to setting PermSize to MaxPermSize? (Essentially saying that the initial
>   product_pd(uintx, MetaspaceSize,
>  \
>           "Initial size of Metaspaces (in bytes)")
>  \
>   \
>   product(uintx, MaxMetaspaceSize, max_uintx,
>   \
>           "Maximum size of Metaspaces (in bytes)")
>  \
> Those might even be at the same lines as PermSize and MaxPermSize used to
> be  :-)
>  size of the meta space is its maximum size
>> and that Max/Min free ratio must be ignored.) Anyway, I'll look at the
>> code
>> and play with the JVM to learn more, but it would be
>> great if you folks could also put out a brief whitepaper giving an
>> overview
>> of the implementation and
> Sounds like you've blocked out of your memory what life is like here.  :-)
>  Whitepaper?  More likely
> sparse release notes.
>  describing the transition to the new perm gen world and how one might size
>> these thresholds so as to empirically
>> "right-size" the heap based on the GC log data etc.
> That's actually something we don't know yet.  Performance seems to be
> neutral and I'll take that
> given the number of lines we've touched.  And we do have more performance
> measurements
> to do.
> Jon
>> thanks a lot again! And sorry for hijacking the review thread for this
>> side-conversation.
>> -- ramki
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