On Thu, 2007-02-15 at 07:57 +0200, Michael S. Tsirkin wrote: > > The choice of 32/64 bit default is done on a per arch basis. With > > x86_64/i386, the increased number of CPU registers in 64bit mode > > outweighs the increased code bloat that goes along with 64bit mode. On > > PPC, no such register benefit exists for 64bit mode. As such, 32bit > > apps on PPC are faster than the equivalent 64bit apps up to the point at > > which a 4GB address space becomes a problem. Correspondingly, the > > default binaries on PPC are 32bit, and only those that *need* to be > > 64bit are. While a customer's application may need >4GB address space, > > certainly all the ibutils, diags, opensm, etc. do not. As a result, we > > compile all of those utilities as 32bit by default on PPC. We also ship > > all the libs as both 32/64bit so users can select the appropriate > > environment for their particular application (with the exception of > > dapl, which doesn't support 32bit and for which I filed a bug around the > > time of OFED 1.1). > > So, what you suggest is - build 2 types of libraries, but on PPC make > binaries 32 bit? That's easy - do others agree to this approach?
Yep, that's what we do.
> Another option is to build binaries with whatever type of binary
> gcc without extra flags generates by default.
Usually this should work, but I don't rely on that since we also support
s390/s390x (although not with Infiniband, but the OpenMPI alternative
that we shipped with RHEL4, lam, gets compiled on s390/s390x) and that
pair is a bit of an odd mix and I don't have one setting here at my
house where I work, so it's hard for me to confirm that just leaving
things to happen by default works as anticipated. If they would ever
make an s390 that uses less than a gigawatt of power and heats less than
a large sized convention center, that could change... ;-)
--
Doug Ledford <[EMAIL PROTECTED]>
GPG KeyID: CFBFF194
http://people.redhat.com/dledford
Infiniband specific RPMs available at
http://people.redhat.com/dledford/Infiniband
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