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    DateSun, 18 Dec 2005 00:55:54 +0100
    FromAdrian Bunk <>
    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.
    
    cu
    Adrian
    
    [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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