Sorry, Mr. pizza ...

Posted Apr 17, 2008 20:34 UTC (Thu) by jzbiciak (guest, #5246)
In reply to: Sorry, Mr. pizza ... by bronson
Parent article: My kid hates Linux (ZDNet)

If 64 bit pointers are really that big a deal, how come the EDA guys don't use 4GB memory pools with 32-bit offsets? That's way you get the speed and huge memory space of 64 bits with the space efficiency of 32 bit. Seems like a win-win.

Sounds like a maintenance nightmare to me, particularly if the code base is shared between 32-bit and 64-bit worlds, and if any portion of the data set has an index larger than 2³²-1. The reason I say "index" is that these pools could be homogeneous pools of structures, and so the addressed memory in that pool could actually be as large as 2³² * sizeof(struct whatever), rather than just 2³² bytes.

Sure, on 64-bit machines you get the compact representation. But, on all machines that share that code base, you add an additional indirection to compute your final pointer, and you've thrown up partitions in your memory map based on where these pools are. If your problem doesn't partition into pools nicely, you're hosed.