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SubjectRe: [openib-general] Re: [PATCH 13/13] [RFC] ipath Kconfig and Makefile
On Sat, Dec 17, 2005 at 02:54:44PM -0800, Robert Walsh wrote:
> > The driver shouldn't use assembler code and therefore no longer depend
> > on X86_64.
> Agreed about the assembler, but one way or the other, x86_64 is the only
> arch we support.

There's a difference between "technically supported by the driver" and
"officially supported for our costumers":

It's fine if you tell the costumers buying your hardware "anything else
than 64bit x86_64 kernels is completely unsupported", but for getting
your driver included into the kernel it should be 32bit clean [1] and
should also work for people using 32bit kernels on an Opteron.

> > -O3 doesn't make much sense since the fight for producing the fastest
> > code is between -O2 and -Os.
> Makes many nanoseconds of difference to us for our latency numbers. At
> the low latency numbers we measuring (1.29us), this is a very important
> difference to our customers.

There's no doubt that this is important for your customers.

What surprises me is that -O3 turned out to be the fastest flag for you.

Can you send numbers comparing -Os/-O2/-O3 (without -g3, preferable with
gcc 4.0) including a description what and how you are measuring?

> Regards,
> Robert.


[1] not long ago, it used to be the other way round that drivers weren't
64bit clean...


"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed

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