Pls review 6887571

[Y.S.Ramakrishna at Sun.COM]

Hi Paul --

Looks good (and about time too!).
Should the parameters whose defaults are now
uniform across platforms migrate back to globals.hpp
from their current lobals_*.hpp locations? Or do you
see the need for continuing to keep them in platform-specific
globals_*.hpp?

-- ramki

On 10/02/09 07:32, Paul Hohensee wrote:
> 6887571: Increase default heap config sizes
> 
> Webrev at
> 
> http://cr.openjdk.java.net/~phh/6887571/webrev.00/
> 
>  From the CR description:
> 
> The default client vm heap config since ~2000 has been the equivalent of
> 
> -Xmx64m -XX:OldSize=4m -XX:NewSize=2m -XX:NewRatio=8
> -XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=15
> 
> for sparc32, and
> 
> -Xmx64m -XX:OldSize=4m -XX:NewSize=1m -XX:NewRatio=12
> -XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=15
> 
> for x86.  OldSize and NewSize are the initial committed sizes of the old
> and young gens respectively.  A full gc is required to increase the 
> committed
> size of the old gen.
> 
> At the time, 64m was half of the 128m of memory typically available on 
> high-end
> desktops, many client applications were satisfied with small heaps 
> (hence the
> low -Xms value), and gc times were such that the young gen had to be 
> fairly small
> in order to minimize pause times.
> 
> Since that time, low end desktops and laptops, as well as netbooks and 
> smartbooks,
> typically come with 256m, client applications have become much more 
> "server-like",
> and we've realized that small young gen sizes increase the frequency of 
> young gcs
> and the amount of transient data promoted to the old gen to levels that 
> noticeably
> impact startup and steady-state performance, principally by provoking 
> full GCs.
> We also note that young gen collection times are proportional to the 
> total survivor
> size rather than young gen size and that small (in absolute terms) 
> survivor spaces
> cause promotion of transient objects, thereby eventually provoking 
> unnecessary
> full GCs.
> 
> This change make the default heap config
> 
> -Xmx128m -XX:OldSize=14m -XX:NewSize=4m -XX:NewRatio=2
> -XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=15
> 
> I.e., it leaves SurvivorRatio and MaxTenuringThreshold alone, but 
> increases absolute
> survivor space size significantly.  We still want as many objects to die 
> in the young
> gen as possible, so MaxTenuringThreshold reamins at maximum.  NewRatio is
> set to the server default of 2, thereby increasing reducing the number 
> of young collections.
> 
> JavaFX startup benchmark runs show an almost 11% improvement, while generic
> client startup benchmark runs show up to 14% improvement.  Footprint 
> increases
> somewhat, ranging from 2% for noop to 37% for netbeans.
> 
> Thanks,
> 
> Paul
>