JEP 173: Remove Rarely-Used Combinations of Garbage Collectors

Bengt Rutisson bengt.rutisson at
Thu Dec 6 13:23:10 UTC 2012

Hi Kirk and Ramki,

On 12/6/12 12:05 AM, Srinivas Ramakrishna wrote:
> I am thinking that if we have a "test case" or publicly available 
> application that can serve as a "witness" to this, it would
> allow us to learn a few useful things on how regular CMS might do 
> better for such apps, and understand the basis of
> this difference. (Unless you have already analysed it and can share 
> your summary of it.)

Yes, I totally agree with this. If there are cases where i-CMS is better 
than regular CMS we need to understand why and should try to get CMS to 
perform as well (or better). This is a much more appealing solution to 
me than to keep the extra complexity that i-CMS introduces.

Kirk, if you have log files of runs with CMS and i-CMS it would be great 
if you can pass them along. I would be very interested in analyzing why 
i-CMS would preform better than CMS.


> thanks!
> -- ramki
> On Wed, Dec 5, 2012 at 3:01 PM, Srinivas Ramakrishna 
> <ysr1729 at <mailto:ysr1729 at>> wrote:
>     Hi Kirk --
>     On Wed, Dec 5, 2012 at 2:48 PM, Kirk Pepperdine <kirk at
>     <mailto:kirk at>> wrote:
>         Hi all,
>         The JEP's are coming in fast and furious. There is a customer
>         use case for iCMS.. it's used by low latency applications...
>         and quite successfully in fact. iCMS manages large heaps much
>         better than CMS does which translates into more manageable
>         pause times... I've got logs from a number of customers that
>         rely on iCMS.
>     This is very interesting indeed (and something i had vaguely heard
>     a few years ago from the general grapevine, although never
>     actually understood
>     why it must be so). Could you go a bit deeper on why this is so?
>     What exactly is it about doing a "slow, spread-out, incremental
>     CMS collection"
>     that makes it work better than bang-bang vanilla CMS in large
>     multi-core, server environments? Perhaps the insights from that
>     might translate into
>     something useful for vanilla CMS?
>     Your experience does indicate that we must proceed with some
>     caution here before we deprecate iCMS, given it might still have
>     some useful life
>     (notwithstanding my own instincts to the contrary -- in server
>     environments -- expressed in an earlier email before I had seen
>     yours).
>     thanks.
>     -- ramki
>         Regards,
>         Kirk
>         On 2012-12-05, at 11:10 PM, mark.reinhold at
>         <mailto:mark.reinhold at> wrote:
>         > Posted:
>         >
>         > - Mark

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