Pls review 6887571

[Jon Masamitsu]

Paul,

Just a couple of comments from the .01 version
of the webrev.  I haven't started the .02 version
yet so may have more comments after I do.

Jon

arguments.cpp

1105       InitialHeapSize = min_new + OldSize;

Use FLAG_SET_ERGO()

FLAG_SET_ERGO(uintx, InitialHeapSize, min_new + OldSize);

Sometimes in the setting of the GC policies we like to
know how the flag was set.

I like ErgoHeapSizeLimit instead of
MaxErgoHeapSize but just my preference.



On 10/27/09 09:26, Paul Hohensee wrote:
> 6887571: Increase default heap config sizes
> 
> Webrev here
> 
> http://cr.openjdk.java.net/~phh/6887571/webrev.01/
> 
> Some background:
> 
> The default client vm heap config since 2000 for sparc32 has been the 
> equivalent of
> 
> -Xmx64m -XX:OldSize=4m -XX:NewSize=2m -XX:NewRatio=8
> -XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=15
> 
> and for 32-bit x86
> 
> -Xmx64m -XX:OldSize=4m -XX:NewSize=1m -XX:NewRatio=12
> -XX:SurvivorRatio=8 -XX:MaxTenuringThreshold=15
> 
> OldSize and NewSize are the initial committed sizes of the old and young 
> generations
> respectively.  A minor gc is required to increase the committed size of 
> the young gen,
> while 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 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 a small young gen size increases 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.
> 
> This change extends server class heap sizing to the client with a few 
> changes.
> Server heap sizing ergonomics should be unaffected.
> 
> 1. NewRatio is set to 2 for all platforms to accomodate an increase in 
> transient data size.
> 
> 2. SurvivorRatio is set to 8 for all platforms.  It was 8 for every 
> platform except
> 64-bit x86 (where it was 6) in any case, so it isn't a big change.
> 
> 3. MaxTenuringThreshold is left at 15 (the maximum).
> 
> 4. I added MaxRAM, whose implemented definition matches the current 
> comment for DefaultMaxRAM
> in globals.hpp.  MaxRAM is the maximum physical memory size used to 
> compute MaxHeapSize
> rather than the maximum possible value of MaxHeapSize set by 
> ergonomics.  I replaced
> DefaultMaxRAM with MaxErgoHeapSize for the latter purpose.  I added 
> support for a new
> argument type, uint64_t, and used it as the type of MaxRAM.  uintx 
> doesn't have the necessary
> range on 32-bit systems: a user might want to specify 4g for MaxRAM on a 
> 32-bit system.
> 
> 5. The other Default* switches have been stripped of the "Default" 
> prefix, since to me their
> values are just as much "default" values as the values of any of other 
> vm switch, and those don't
> have a "Default" prefix.  I left DefaultMaxRAMFraction as a synonym for 
> MaxRAMFraction for
> the moment because QA uses it.  When they change to MaxRAMFraction, I 
> intend to remove
> DefaultMaxRAMFraction.
> 
> 6. In arguments.cpp, set_heap_size() replaces set_server_heap_size() and 
> is used for everything
> except CMS.  CMS has it's own, incompatible (I know: I tried it), heap 
> sizing ergonomics.
> 
> 7. The minimum committed size of the old gen (OldSize) remains at 4m and 
> the minimum
> committed size of the young gen (NewSize) increases to 4m.  Note that 
> these are the minimum,
> not initial sizes.  NewSize is made common to all platforms.
> 
> 8. I added a switch InitialHeapSize that can be used to set the initial 
> committed size of the heap.
> Absent specification by InitialHeapSize, the initial committed size is 
> 1/64th of physical memory
> or OldSize + NewSize, whichever is larger.
> 
> 9. I cleaned up some formatting, esp. in globals.hpp.
> 
> 10. The default MaxHeapSize is raised from 64m to 96m.  For systems with 
> <= MaxHeapSize
> physical memory, the minimum heap size is 1/MinRAMFraction of physical 
> memory.  The
> default value of MinRAMFraction is 2.  Thus, a 256m box gets a 96m heap, 
> as does a 128m
> box, but a 96m box gets a 48m heap and a 64m box gets a 32m heap.  The 
> default values of
> MaxRAM and MaxRAMFraction bound the maximum heap size to 256m for the 
> client vms,
> 1g for 32-bit server vms and 32g for 64-bit server vms.  The values for 
> the server vms are
> the same as before.  I picked 256m for client because I wanted to bound 
> resource utilization
> on client systems.  Also, benchmarks runs showed no extra benefit from 
> going to 512m heaps.
> 512m is the safe maximum for the serial collector.
> 
> Thanks,
> 
> Paul
> 
> 
> 
> 
>