Re: [9fans] Re: Threads: Sewing badges of honor onto a Kernel

[lucio@proxima.alt.za]

> In most people's minds message passing passing usually means 'move the
> data from this hole here to that hole there'. Of course in any optimized
> situation (shared memory) this can be done with pointer hacks. And even in
> the optimized situations, message passing libraries as measured are at
> least one or two orders of magnitude slower than simple 'hand the pointer
> around', esp. on shared-memory and CC-NUMA systems -- I can give you
> references, if you wish, or you can google Jim Taft's work at NASA AMES.  
> There's a hardware reason for the performance difference. 
> 
I don't understand what is being measured in this case.  Surely one
doesn't go to Linus Torvalds to get specifications for the design of
on operating system for a specialised piece of equipment?  Ever since
before Unix, the emphasis has been on portability, OS design has
sacrificed performance to the objective of being able to continue
using applications on the newer, faster hardware.  At least, that is
how it seems to me.

> Do people care about that difference? Yes! If you just dropped $10-20M on
> a computer, do you want to get $500K worth of performance out of it, or
> would you rather get more like $10-20M out of it? Your call. Better yet, 
> assume your job rests on the decision, then make the decision :-)
> 
Sure.  But then did the price include optimised software, or do you
expect to run some off-the-street operating software on your
performance host?  By the time you spend money in that order of
magnitude, you can afford to employ the few software architects that
still understand low-level programming and get them to squeeze every
bit of performance out of your horse.  Or would you ask Torvalds to
drive the next generation of Grand Prix Ferrari to win the racing
season?

> Point to Linus on this one, I think. Sorry.
> 
No ways, it's a mismatch.  Torvalds just organically grew an OS from
Minix, for the Intel architecture.  The Great Barrier Reef likewise
grew organically, but is unlikely to be recommended as the dam wall
for the Yellow River.

> On another note, the Linux guys are not kernel designers in many senses of
> that word. From my point of view Linux is an extremely competent
> implementation of some really good and some really bad OS ideas -- ranging
> from V6 Unix syscall interface to later ideas such as VFS.  And, like it
> or not, it works very very well for many people, including the several
> thousand systems we have here that run it for high performance computing.
> Credit where credit is due.
> 
One can't hold against Torvalds the decision to stick to the Unix
paradigm, no one else had much of a better choice at the time.  But to
defend it in the face of obvious obsolescence is unforgivable.  And to
suggest that performance is a significant factor in the design of a
generic operating system is laughable.

> And, that said, I'm still gradually moving my existence over to Plan 9. 
> 
Which makes you a lot more practical than Torvalds.  Presumably
microoptimisations are not saving you millions of dollars.  Nor me :-)

++L