O bitter is the knowledge that one draws from the voyage!from my facebook group on systems, networking and deez high-performance nuts, aka Our Cachelines go to 0x11:
The monotonous and tiny world, today
Yesterday, tomorrow, always, shows us our reflections,
An oasis of horror in a desert of boredom!
Must we depart? If you can do so, remain;
Depart, if you must. Someone runs, another crouches,
To deceive that vigilant and fatal enemy,
Time! Ah, there are some runners who know no respite
- Baudelaire, of whose posse i am a part
no one will evict us from this paradise von neumann has created!
echoing the words of david hilbert (Aus dem Paradies, das Cantor uns geschaffen, soll uns niemand vertreiben können...Wir müssen wissen — wir werden wissen!), let us ask (in the words of the Jurassic Park girl):
is multicore really going to change everything?
there's always been a search for parallelism's exploitation -- SIMD's been around since CDC/Cray, as have architectural techniques for mining ILP. These, of course, are to an extent compiler-governable, and don't offer the scaling of multicore for anything but a very small subset of problems (although see Nvidea G80, for instance, to see such problems pwned up on). SMP was supposed to usher in a new parallel age. Of course, you can't arbitrarily scale mobo's -- same for clusters and interconnects (although these are fantastic for tasks with weak latency requirements). So, multicore promises scalability, low latency, and a friendlier caching/execution model (basically a multiple or factor of NUMA). That's what makes it meaningful.
But is the sky falling?
Here's some great links I've recently come across:
Keith Adams of VMWare, more (read the Bryan Cantrill post linked from the former!)
Bartosz Milewski, Reliable Software
Steve Reinhardt, Interactive Supercomputing / Cray Research
and everyone ought read this article from 2008-11 CACM, by a group at IBM's Watson Lab. Just say NO! to Software Transaction Memory!
on microkernels, zero-copy tcp, shoes and ships and sealing wax...
why is it every time i get real excited about something, it ends up reducing to reimplementing some kernel abstraction in user space?
maybe the big benefit of microkernels isn't protection between kernel modules, but the lack thereof from user space -- when you don't need to maintain the fourth wall, you stop thinking in terms of write() and start thinking in terms of vmsplice(). this is paradoxical, because microkernels are supposed to slow things down (precisely due to erecting ISOC/POSIX-like (read: von neumann and unix-like) barriers between kernelspace entities).
of course, like everything else that's a benefit of microkernels, this is present in a well-engineered "monolithic" kernel -- after all, i reference 'thinking in terms of vmsplice()'.
so perhaps the right thing to do is a vmsplice()-infused microkernel. this might be what Engler et al were trying to do back in 1995 on the exokernel project at MIT, even if time's arrow didn't net the memo.
note how badly freebsd's zero-copy idea is braindamaged -- an homage to the difficulty of doing a kernelspace ARQ protocol based on userspace data without a copy. look at designs of vmsplice()/TCP integration, and watch the COW being chased down the same road. zero-copy kernelspace TCP is like trying to apply gross RCU to a structure that, at times, blows up to thousands of pages -- babe, it ain't gonna happen. but if we move TCP into userspace, and move to a zero-copy packet socket, what can we do? what would be the ramifications for a van jacobson-based RX? what would be the ramification for NIC-based TOE engines and Intel I/OAT?
how on earth are we gonna handle 10Gb NICs, gentlemen?
on a closing note, it's been an outstanding fucking five years allowing y'all intimate views into this mind afflicted (less afflicted these days, I think -- work's a soothing balm indeed, and grad school more so), a chance to look backwards from behind mine own eyes, but frankly:
- it got to the point back in early 2007 where i would be like, "ooooh, i need to blog that when i get home!" i can think of few traits more repulsive -- or prone to timesinkery
- forthright discussion of la vida dank is, sadly, no longer compatible with my lifeplan (i have, of course, no intention of cleaning things up (save errors of grammar or spelling, which will be ruthlessly annihilated as always))
More than anything else, we've developed our vocabularies, every one of us (I'm pretty confident saying this). Our lives will be better for it!
I met a girl who sang the bluesI'm thinking about starting a semi-serious blog, with a post or two a month, one of those things that reads like a 50-page resume and is a 50-page resume, a portfolio of preening for employers and guilds and one hundred million eager engineers from the East (no, further east, the east that's to the west). I love to teach, love to talk about computer, science and computer science, and think I, from time to time, have things worth sharing...
And I asked her for some happy news,
But she just smiled and turned away.
I went down to the sacred store
Where I'd heard the music years before,
But the man there said the music wouldn't play.
- Don McLean, American Pie
I wanna exchange this CD!
The Pimp-Trick-Gangsta-Clique CD? Why?
It won't play right!
- Outkast, Aquemini
ONE LAST CLICHE POETRY BLOCKQUOTE? OH YES. This is the last one, folks, but it's an old favorite and I bet some of you can recite it with me...
I saw the best minds of my generation destroyed by madness, starving hysterical naked,
dragging themselves through the negro streets at dawn looking for an angry fix,
angelheaded hipsters burning for the ancient heavenly
connection to the starry dynamo in the machinery of night,
who poverty and tatters and hollow-eyed and high sat up smoking in the supernatural darkness of
cold-water flats floating across the tops of cities contemplating jazz,
who bared their brains to Heaven under the El and
saw Mohammedan angels staggering on tenement roofs illuminated,
who passed through universities with radiant cool eyes
hallucinating Arkansas and Blake-light tragedy among the scholars of war,
who were expelled from the academies for crazy & publishing obscene odes on the windows of the skull,
who cowered in unshaven rooms in underwear,
burning their money in wastebaskets and listening to the Terror through the wall...
battered bleak of brain all drained of brilliance in the drear light of Zoo,
who sank all night in submarine light of Bickford's floated out and sat through the stale beer after
noon in desolate Fugazzi's, listening to the crack of doom on the hydrogen jukebox,
who talked continuously seventy hours from park to
pad to bar to Bellevue to museum to the Brooklyn Bridge,
lost battalion of platonic conversationalists jumping
down the stoops off fire escapes off windowsills off Empire State out of the moon,
yacketayakking screaming vomiting whispering facts
and memories and anecdotes and eyeball kicks
and shocks of hospitals and jails and wars,
whole intellects disgorged in total recall for seven days
and nights with brilliant eyes, meat for the Synagogue cast on the pavement,
who vanished into nowhere Zen New Jersey leaving a
trail of ambiguous picture postcards of Atlantic City Hall,
suffering Eastern sweats and Tangerian bone-grind-ings and
migraines of China under junk-with-drawal in Newark's bleak furnished room,
who wandered around and around at midnight in the
railroad yard wondering where to go, and went, leaving no broken hearts...
who coughed on the sixth floor of Harlem crowned
with flame under the tubercular sky surrounded by orange crates of theology,
who scribbled all night rocking and rolling over lofty
incantations which in the yellow morning were stanzas of gibberish,
who threw their watches off the roof to cast their ballot
for Eternity outside of Time, & alarm clocks fell on their heads every day for the next decade,
who cut their wrists three times successively unsuccessfully, gave up and were forced to open antique
stores where they thought they were growing
old, and cried...