Messages in this thread | | | From | David Lang <> | Date | Mon, 14 Jan 2002 15:17:07 -0800 (PST) | Subject | Re: Hardwired drivers are going away? |
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my apologies for the terminology errors, I was trying to go from memory from the thread here late last year.
David Lang
On Mon, 14 Jan 2002, Brian Gerst wrote:
> Date: Mon, 14 Jan 2002 18:12:43 -0500 > From: Brian Gerst <bgerst@didntduck.org> > To: David Lang <dlang@diginsite.com> > Cc: Ian Molton <spyro@armlinux.org>, linux-kernel@vger.kernel.org > Subject: Re: Hardwired drivers are going away? > > David Lang wrote: > > > > the impact is in all calls to the module, if they are far calls instead of > > near calls each and every call is (a hair) slower. > > > > so the code can be the same and still be slower to get to. > > > > you can argue that it's not enough slower to matter, but even Alan admits > > there is some impact. > > > > David Lang > > Let's get the terminology right here (for x86 at least): > Far jump: Changes to a new code segment, absolute address > Near jump: Same code segment, 4-byte relative offset > Short jump: Same code segment, 1-byte signed offset > > The kernel never uses far jumps except for some BIOS calls and during > booting. The difference betwen near and short jumps is very minute. > Short jumps are limited to +/- 128 bytes, so are really only applicable > for small loops. All function calls between object files must be near > jumps, as the assembler does not not know the distance of an unresolved > symbol and must assume the largest possible offset. > > -- > > Brian Gerst > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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