Re: amd64: svs

[Eduardo Horvath <eeh%NetBSD.org@localhost>]

On Thu, 11 Jan 2018, Martin Husemann wrote:

> On Thu, Jan 11, 2018 at 08:14:59PM +0100, Jaromír Dole?ek wrote:
> > Okay, I'll look into this. The feature seems pretty simple to use, though
> > it will need
> > some care to allow inactive processes to relinguish PCID when there is
> > shortage.
> 
> All sane architectures are already using it ;-)
> 
> Sparc64 uses a pretty simple scheme, see pmap.c:ctx_alloc:
> 
>         mutex_enter(&curcpu()->ci_ctx_lock);
>         ctx = curcpu()->ci_pmap_next_ctx++;
> 
>         /*
>          * if we have run out of contexts, remove all user entries from
>          * the TSB, TLB and dcache and start over with context 1 again.
>          */
> 
>         if (ctx == curcpu()->ci_numctx) {
> 
> 
> If we start doing something more clever, we should make it MD and change all
> existing architectures to it.

If you look in the CVS history you will see that I originally had a much 
more clever implementation.  The claim back then is that the current 
implementation (stolen from MIPS I believe) was simpler and performed 
better.  I didn't necessarily agree at the time but didn't want to argue 
the point.

Eduardo