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Re: XFree 4.1


Lot of answers :-)

I have till now no time to take a look at the xserver sources, but I
downloaded the UserManual and programming manual of the 68060. And take a
look at the icache_flush makro.
So there are still some questions for me:

Alan: How do you flush the icache? I don't think that makro works =>
privileged instruction. And what is the difference to the 68060 and why?
And a general question: Why is it necesarry to flush the cache? I mean on my
machine sometimes it works sometimes not (I hate such errors) maybe it is
possible to do another workaraound? So where the icache has to be flushed
(which files)?

I hope I get some answers :-)


----- Original Message -----
From: Alan Hourihane <alanh@fairlite.demon.co.uk>
To: Richard Zidlicky <rz@linux-m68k.org>
Cc: Kars de Jong <jongk@linux-m68k.org>; Gerhard Täubl <gtbiv@eunet.at>;
Sent: Thursday, January 09, 2003 4:48 PM
Subject: Re: XFree 4.1

> On Thu, Jan 09, 2003 at 03:37:16PM +0100, Richard Zidlicky wrote:
> > On Wed, Jan 08, 2003 at 09:34:40PM +0000, Alan Hourihane wrote:
> >
> > > It's only the instruction cache we need to flush. Not the whole cache.
> > > I notice in asm-m68k/pgalloc.h there's a specific flush_icache() macro
> > > to do just that.
> >
> > all cacheflush instructions are priviliged. There is a little trick
> > to force datacache flush without a syscall using the move16 insn, this
> > would however work on 68040/060 only and doesn't solve the issue with
> > the program cache.
> >
> > > There are only two relocations used in the loader for m68k at the
> > > and I doubt it's going to be a massive performance hit. But having a
> > > working loader is a step in the right direction even if it is slower.
> > > We can work out how to speed it up later.
> >
> > it is slow enough even without the loader. Every sort of relocation
> > is likely to slow down program startup drastically, this is because
> > the relocation does force a tremendeous lot of pages to be paged in
> > just to fix the relocation address - in many cases those pages aren't
> > ever touched again. Effectively this defeats demand paging, the
> > additional cacheflush is just the tip of the iceberg and perhaps even
> > irelevant compared to the time spent with paging.
> >
> > It would be certainly good to have the module loader, but for the
> > average m68k user this is of no benefit and so I think m68k should
> > default to statically linked Xserver.
> Your loosing a lot of configurability without the loader.
> If no one is interested here, I hope to get time to poke at this some
> more. Unfortunately I only have a WarpEngine 4040 which nicely does
> the cache flushing for me and so the loader works regardless for me.
> Alan.
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