Re: 4.01 panic/lock issues?

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 --