Re: [C400-L] RE: Porting C Linux to ILE C: Performance problem

[Blair Wyman <blairw@xxxxxxxxxx>]

AFAIK, the 4GB limit on (teraspace) allocations addressable by a 16-byte
pointer is an artifact of the 4-byte unsigned size_t parameter to malloc().

(To get anything over 16MB in a single allocation you must be using
teraspace -- single-level store segments are 16MB in size.)

Now, for fun numbers:

The theoretical limit for 16-byte pointers is ( 2^128 - 1 ) or
340,282,366,920,938,463,463,374,607,431,768,211,455 bytes.

The theoretical limit for 8-byte pointers (used by the PowerN hardware) is
( 2^64 - 1 ) or 18,446,744,073,709,551,615 bytes.

The theoretical limit for teraspace addresses is 2^40-1 or
1,099,511,627,775 bytes (1 terabyte -- hence the name).

HTH.

-blair

  ___   _           Blair Wyman                  IBM Rochester
 ( /_)  /  _  ' _   (507)253-2891            blairw@xxxxxxxxxx
__/__)_/_<_/_/_/_'  Opinions expressed may not be those of IBM



                                                                           
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4gb is the limit for 16 byte pointers.
Larger allocations require 8 byte pointers and DTAMDL(*LLP64)

Apparently these 8 byte pointers should also perform better.
ILE concepts, Chapter 4.


> It sounds to me though, that the original poster really needs to look at
the
> teraspace compile options.  With it, you can allocate up to 4GB blocks
(on
> V5R1).

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