Re: [PATCH] i386 rw_semaphores fix

[David Weinehall <tao@acc.umu.se>]

On Wed, Apr 11, 2001 at 02:20:28AM +0200, Andi Kleen wrote:
> On Wed, Apr 11, 2001 at 02:13:18AM +0200, David Weinehall wrote:
> > > 
> > > Yes, and with CMPXCHG handler in the kernel it wouldn't be needed 
> > > (the other 686 optimizations like memcpy also work on 386) 
> > 
> > But the code would be much slower, and it's on 386's and similarly
> > slow beasts you need every cycle you can get, NOT on a Pentium IV.
> 
> My reasoning is that who uses a 386 is not interested in speed, so a little
> bit more slowness is not that bad.

My reasoning is that the choice of computer is a direct function of
your financial situation. I can get hold of a lot of 386's/486's, but
however old a Pentium may be, people are still reluctant to give away
those. Doing the sometimes necessary updates on my 386:en is already
painfully slow, and I'd rather not take another performance hit.

> You realize that the alternative for distributions is to drop 386 support
> completely?

Yes, I realise that. But if _distribution X_ drops support for the 386,
there's always _distribution Y_ available with it still in, while if
we give the glibc-people the thumbs up saying "Ignore the 386 users from
now on", every distribution will get lousy performance on those machines.

> Most 386 i've seen used for linux do not run multi threaded applications
> anyways; they usually do things like ISDN routing. Also on early 386 with
> the kernel mode wp bug it's a security hazard to use clone().

Well, not all 386:en are early...


/David
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