JEP 132: More-prompt finalization

[Dmitry Samersoff]

Tony,


On 2012-01-06 14:34, Tony Printezis wrote:
> Vitaly,
> 
> Sure, but if the GC detects that the load is low it doesn't know whether
> the load will remain low for 5 ms or 5 hours (and it's impossible to
> know, maybe not even the application knows). I can already imagine the
> bug reports: a spike suddenly happened in the market and the JVM was
> "locked up" for several seconds!!!

To be more practical, lets consider a vital case - a shop selling
something to particular region. (e.g city's best pizza)

It has clear visible pick hours (evening) and clear visible spare time
(early morning)

So cu would like to have as much free resources as possible at a pick
hours.  Solution widely used today - create a cluster, then restart
nodes one by one at a spare time.

What we(java) can do for such case:

   1 (simple, doable today). Give a way to setup ergonomic profile e.g.
something like -XX:PreferredGCTime. During this time VM sets GC
parameters to collect as much as possible at the cost of higher
load by GC thread.

  2. (advanced) Collect heap usage statistics and calculate a
probability of low load time.

-Dmitry

-- 
Dmitry Samersoff
Java Hotspot development team, SPB04
* There will come soft rains ...