code review 6828055: runtime: allow up to 128GB of memory 64-bit platforms

runtime: allow up to 128GB of memory 64-bit platforms

On 64-bit platforms increase the arena from 16GB to 128GB.
Increasing this further might require GC work.  Slight cleanup
to avoid assuming pages are 4K.

[cw, 2012-11-10 06:34:56]

Hello rsc@golang.org, iant@golang.org (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://go.googlecode.com/hg/

[dave_cheney.net, 2012-11-10 06:46:24]

I would like to see a discussion of this change on golang-{nuts,dev} before the
implementation.

[albert.strasheim, 2012-11-11 18:36:03]

Hello

On Saturday, November 10, 2012 8:46:26 AM UTC+2, Dave Cheney wrote:
>
> I would like to see a discussion of this change on golang-{nuts,dev} 
> before the implementation. 
>

I tried to write up some thoughts here:

http://code.google.com/p/go/issues/detail?id=2142#c16

Long story short, it might be worth it to consider a runtime function 
equivalent for Java's -Xmx to avoid misbehaving 64-bit Go programs running 
far past 16 GB.

Regards

Albert

[rsc, 2012-11-12 19:33:45]

LGTM

This has been on the todo list for a while and discussed multiple times. I am
not sure what is left to discuss. But I will wait to see what people say.

https://codereview.appspot.com/6828055/diff/5001/src/pkg/runtime/malloc.h
File src/pkg/runtime/malloc.h (right):

https://codereview.appspot.com/6828055/diff/5001/src/pkg/runtime/malloc.h#new...
src/pkg/runtime/malloc.h:136: #define	MaxMem	(1ull<<(MHeapMap_Bits+PageShift))
Please use ULL like the code that was replaced.

[rsc, 2012-11-12 19:34:28]

Also please add "Update issue 2142." to the end of the CL text.
I will prepare a separate CL changing the memory base that will mark it as
fixed.

[remyoudompheng, 2012-11-12 19:40:03]

The comment in malloc.goc (runtime·mallocinit) should be updated. Or
be less precise about the particular amount of memory.

Rémy.

[rsc, 2012-11-12 19:49:17]

Actually, this CL is so small that it probably makes sense for me to roll it
into the changes to malloc.goc. I will still wait a day to see if anyone has any
comments.

[cw, 2012-11-15 07:16:27]

*** Abandoned ***