Java: All about 64-bit programming

vanillajava.blogspot.com

24 points·AndreyKarpov··6 comments

As of mid 2011, for £1K you can buy a PC with 24 GB of memory and for £21K you can buy a server with 512 GB of memory.

I'm not sure where he gets his computers from but those prices seem to be at least a few years away.

http://www.alternate.de/html/product/GeIL/DIMM_24_GB_DDR3-10...? <- 180€ for 24gb of memory... i think his prices are pretty accurate.

http://vanillajava.blogspot.com/2011/07/new-toy-for-home.htm...

The computer runs at 3.8 GHz and came with two 20" screens. ;)

The £21K computer is a Dell incl. tax retail price from their web site.

Perhaps it sounds cheaper in £ instead of $ or € ;)

You also have to remember that to run 64-bit applications, you must specify the -d64 flag. Otherwise your app will run in 32-bit mode!

AFAIK -d32 was the default on some versions of Solaris, but -d64 is the default now. Windows doesn't support these options. Linux does support -d32 but it has to be installed seperately, otherwise -d64 is the default for a 64-bit JVM.

A big win for 64bit java over 32bit is that the kernel can provide more memory to the 64 bit process. This is because the java heap has to be 'contiguous' memory, and this is difficult to offer when in 32 bit mode due to memory fragmentation. In 64 bit mode the kernel can cobble together disparate blocks of memory and make it appear contiguous to the process.

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