Feature request: ability to use libeio with multiple event loops

Marc Lehmann schmorp at schmorp.de
Wed Dec 21 20:54:03 CET 2011


On Wed, Dec 21, 2011 at 02:43:14PM +0100, Ben Noordhuis <info at bnoordhuis.nl> wrote:
> > Maybe you have simply the wrong idea about what a context switch is or how
> > a cpu or mmu works.
> 
> Well put in a nicely condescending tone.

Maybe a less arrogant mail might have gotten a more favourable
response? Just sayin...

> Still, you haven't told me what your idea of CPU registers is or how
> they magically stay intact across a task switch. Please enlighten me.

Registers don't need magic to stay "intact" (== have the same value), they
basically never change on their own, instructions must change them. There
are exceptions, but the point is true even then: registers don't change
due to magic, they change because a well-defined process changes them
somehow.

A tasks witch will typically only change the registers it needs to
switch. For example, both MMU and FPU registers are only changed on demand
on Linux, on architectures that allow that.

> Re: task switch vs. context switch: I'm using linux kernel
> nomenclature because it's (IMO) more precise than the overloaded
> concept of a context switch. I know you've posted to the LKML once or
> twice so I assume you have a basic grasp of the kernel's internals.

Maybe you shouldn't use nomenclature that you don't understand well enough
though. I doubt you know what a task switch does in Linux, so why don't
you find it out first before denouncing other people's "ideas"?

In any case, your tone is way too arrogant to deserve a response, so
don'please t make bullshit claims about "my idea" of a register when you
don'admit you t even know what that "idea" is.

If you don't know soemthing, why don't you ask, or googe? Not knowing
is not an issue. Not knowing and showing off this lack of knowledge
arrogantly is a very bad trait.

So why don't you get the processor manual for an arm, intel or amd cpu and
study it, to see what kinds of registers those cpus have, and then work
out when an OS such Linux might want (or be forced) to change these, and
what kind of performance penalties might be associated with that.

-- 
                The choice of a       Deliantra, the free code+content MORPG
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      ---==---(_)__  __ ____  __      Marc Lehmann
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