Re: 4.01 panic/lock issues?

[David Brownlee <abs%NetBSD.org@localhost>]

On Mon, 19 Jan 2009, Bolo wrote:

> > > Anyway, using -m68040 on building packages is too bad..
> >
> >         I believe that the performance penalty of -m68020 on 040 boxes
> >         is great enough that there is real benefit for using -m68040.
> >         Defaulting to -m68020-60 would reduce that need significantly...
>
> Another way of looking at this is that the most common 68k boxes
> are the 020 and 030 boxes.  The 040s and 060s, though wonderful,
> are comparatively rare.
>
> The performance loss of instruction emulation will effect the slower
> machines far more than than the faster boxes, it costs less to emulate
> when a faster CPU is doing the emulation.
>
> We ran a combined 020/030/040 userland (020 + 6888[12]) for a number
> of years.  The performance effects of the emulated instructions on
> the 040 never made a real difference in performance -- they were
> still the fast kids on the block by a large margin.
>
> Specialized workloads which hit the emulated instructions a lot could
> change that.  However for ordinary system / unix / software development /
> math / text processing type things there was no noticeable performance
> loss with the fast machines emulating the "slow" instructions.

        I suspect the ratio has changed over time - a greater
        proportion of the faster 040 and 060 machines (particularly 040
        macs) have been kept than the 020 and 030, precicely because they
        are faster.

        The slowdown of -m68020 => -m68020-60 on 680[23]0 should be
        much less than the slowdown of -m68020-60 => -m68020 on 680[46]0,
        but the way to get a final conclusion is to run the test...

        You should be able to put this into /etc/mk.conf

        .if ${MACHINE_ARCH} == m68k
        CPUFLAGS=-m68020
        .endif

        Then run './build.sh -U -m atari release' (can be done on a nice
        fast box like a beefy AMD/Intel NetBSD or Linux system) to build
        a complete m68020 optimised distribution. Install it and then time
        something relevant - like building a kernel or run apachebench
        against a website, whatever you care about.

        Then replace -m68020 with -m68020-60 and repeat

        At this point I would still prefer -m68020-60 as the default...


--
                David/absolute       -- www.NetBSD.org: No hype required --