SW Weenies: Ready for CMT? 378
tbray writes "The hardware guys are getting ready to toss this big hairy package over the wall: CMT (Chip Multi Threading) and TLP (Thread Level Parallelism). Think about a chip that isn't that fast but runs 32 threads in hardware. This year, more threads next year. How do you make your code run fast? Anyhow, I was just at a high-level Sun meeting about this stuff, and we don't know the answers, but I pulled together some of the questions."
Ready for CMT? Hell no! (Score:3, Funny)
Re:Ready for CMT? Hell no! (Score:2, Funny)
Re:Ready for CMT? Hell no! (Score:4, Funny)
Re:Ready for CMT? Hell no! (Score:3, Funny)
No, that's his brother, Hank.
Schism Growing (Score:2, Insightful)
The parallel are used for intense processing. Research, servers, clusters, databases; anything that can be divided into many little jobs and run in parallel.
The other camp is the average user who just wants fast respons time and to play Doom 3 at 100+ fps.
Re:Schism Growing (Score:2, Insightful)
how much for the best of both worlds? (Score:2)
Just the existance of one such device would heal the rift immediately. Everyone would say... aha! It is only a matter of time before blazing speeds and hardware threading comes to the desktop.
Re:how much for the best of both worlds? (Score:5, Informative)
Simultaneous Multi-Threading is a CPU's ability to concurrently execute mixed instructions from multiple threads. Intel's HT simply 2-ways SMT.
Chip Multi-Threading is a CPU's ability to hold execution states for multiple threads, executing instructions from only one of them at a time unless the chip is also SMT.
In Sun's case, the mid-term plan is to eventually offer 8-ways SMT with 32-ways CMT: the CPU can hold states for up to 32 threads and have in-flight instructions from as many as eight of them.
Re:Schism Growing (Score:4, Interesting)
The most obvious example of this is the GPU, which has been around for a long time. The latest moves toward this trend rumored to be in development are PPUs, Physics Processing Units. How long until game AI evolves enough that we have the need for AIPUs also?
This approach obviously doesn't make too much sense in a general purpose computer because the space of possible applications and types of code to be run are just too large. It makes perfect sense in computers that are built especially to run games though, because we have a very good idea of the different kinds of code most games will have to run. This approach allows each type of code to be run on a processor that is most efficient at that type of code, e.g. graphics code being run on processors that provide a ton of parallel pipelines.
Re:Schism Growing (Score:5, Interesting)
Actually from what I've heard, the entire industry is moving in this direction. The whole idea of out of order processors (OOP) has become outdated. OOP was great. Enabled massive single threaded performance, however the costs (in terms of area and heat dissipation) is enormous.
I just came back from the DaMoN [cmu.edu] workshop where the keynote was delivered by one of the lead P4 developers. He explained the future of microprocessors and said that the 10-15% extra performance that OOP enables just isn't worth it. The Pentium 4 has 3 issue units, but the way things are rarely issues more than 1 instruction per cycle.
We can squeeze more performance out of them, but not much. The easiest method is to go dual core. However if an application must be multithreaded to enable the best performance, what would you rather have . . . 2 highly advanced cores, or 8-10 simple cores that can issue half as many instructions per cycle as the dual core design. Than consider the fact that each core enables 4 threads to run (switch on cache miss/access). It doesn't take a rocket scientist to see that overall performance is improved with this.
The other option is the hybrid core. A single really fast x86 core combined with multiple simpler x86 cores. That way single threaded apps can run fast (until they're converted) and you can get overall throughput from the system without blowing away your power budget on OOP optimizations.
Granted most of this is in the future (within the next 5 years), but IBM's going that way (ala Cell), its within Intels roadmap, Sun is pushing that route etc. I assume AMD has plans to create a supercomputer on a chip . . . unless they wish to be obsoleted.
Phil
Re:Schism Growing (Score:2)
If you're not using an Atari ST, you can probably already exploit a multi-core cpu to your immediate benefit.
Re:Schism Growing (Score:5, Interesting)
Exploring parallelism is a hard issue for many problems. For instance, most of my time I'm compiling C++ code. Usually I just need to compile one file (the one I changed and want to test), and this is not a parallel process.
You'll still benefit from parallelism in two ways. First, a modern computer is rarely doing just one thing. The OS has some threads managing I/O and performing housekeeping operations, and you're probably also listening to some music, and you probably have some other apps running that occasionally need a little computation. So none of that stuff will impede your compile.
Second, even a compiler can benefit from multiple threads, though current compilers don't do it. There are multiple stages in compilation, like pre-processing, lexical analysis, syntax analysis, semantic analysis, intermediate code generation, optimization and code generation. The stages don't need to wait until the previous stage has completed its work on the entire file, so the stages can be parallelized to a large extent. It might even make sense to have multiple threads working on different chunks of the code for more computation-intensive stages, like optimization (which becomes even more important without out-of-order execution).
It seems to me that linking could also be done in parallel with computation, to some degree. To a very large degree if you can guarantee that you don't have any symbols that override library symbols (else a use of a symbol could be linked against a library definition of that symbol before the compiler got around to noticing that you'd defined another definition).
Perhaps the biggest problem with parallelizing compilation and linking to that degree will be I/O. On second thought, probably not, because modern machines have huge amounts of RAM for caching disk files.
In an 8+ core machine, it may make sense to dedicate a core to memory management, also. Even with manual memory management (malloc/free), allocating and releasing memory consumes significant CPU cycles, so I could see value in offloading that to another thread. A "free" operation, from a compute thread's point of view, would be nothing more than notifying the memory manager thread that this block is now available for re-use. The memory manager thread would then take care of all of the bookkeeping needed. The manager could also arrange to have a list of blocks of commonly-needed sizes ready for instant allocation, and could even spend some CPU cycles on analyzing the allocation patterns of the compute threads to try to ensure that blocks are always available when needed. Obviously, pushing that idea further leads naturally to full-blown garbage collection, with fewer concerns about GC pauses.
Although it's true that not all computations can be sped up by multi-threading, lots of them can, including lots that we're used to thinking of as inherently serial processes.
Re:Schism Growing (Score:5, Interesting)
Re:Schism Growing (Score:3, Informative)
Actually, a major point of OO execution is to hide small delays - with the window sizes of modern processors, you can easily hide L1 latencies and possibly hide the latencies of L2, and only pay severely for accesses to main memory. An in-order core is the one that really loses performance as L1 and
Don't worry (Score:2, Informative)
BTW, your "average" user hasn't even played DOOM I, let alone DOOM III. Surfing the web and using e-mail doesn't usually put a lot of strain on a PC.
Re:Schism Growing (Score:2)
imagine a future PC with 32656 CPUs, all running at a measly 40MHz, but each one dedicated to a single object in the game. All they have to do is calc the position of that single object. Might give some interesting results
Re:Schism Growing (Score:2)
What are the other 111 processors doing (32656 + 111 = 2^15-1)? Enforcing DRM?
--
Why the heck doesn't slashcode let me use <sup> and <sub>?
Re:Schism Growing (Score:3, Funny)
Re:Schism Growing (Score:2)
Ah, a PC where latency is king. Rather difficult to optimize, I should imagine.
Re:Schism Growing (Score:2)
I am afraid that is NOT the average user. Maybe the average high end gamer but not user.
Parallel will be of use for the average user. Your typical PC runs about 43 processes. Yes even games will benefit once the game programmers start writing multi threaded code. For your average user I can see where you might even have a bunch of integer processors "sharing" a few blindingly fast CPUs. Sort of like a rever
Re:Schism Growing (Score:2)
Niagara Myths (Score:5, Insightful)
Whatever the clock rate, multiply it by eight and it's pretty obvious that this puppy is going to be able to pump through a whole lot of instructions in aggregate.
Ho hum.
On a good day, with a following wind, Niagara might be able to do 8 integer instructions per second, provided it has 8 independent threads not blocking on I/O to execute.
It only has one floating-point execution unit attached to one of those 8 cores, so if you have a thread that needs to do some FP, it has to make its way over to that core and then has to be scheduled to be executed, and then it can only do one floating-point instruction.
Superb.
The thing is, all of the other CPU vendors with have super-scalar, out-of-order 2- and 4- core 64- bit processors running at over twice to three times the clock frequency.
You do the mathematics.
Argh! (Score:3, Informative)
On a good day, with a following wind, Niagara might be able to do 8 integer instructions per second, I meant per clock cycle, of course, not per second.
The thing is, all of the other CPU vendors with have
I meant "will have" not "with have".
Shame (Score:4, Interesting)
Re:Shame (Score:4, Insightful)
Dude, you're gettin' a Cell! (Score:3, Funny)
I couldn't help it.
Re:Niagara Myths (Score:4, Insightful)
Re:Niagara Myths (Score:3, Funny)
Re:Niagara Myths (Score:5, Funny)
Yes, and I corrected myself straight away in another post. In true slashdot style, the post where I corrected myself got modded down to Offtopic.
Steam Engine - Diesel (Score:5, Insightful)
Re:Steam Engine - Diesel (Score:5, Insightful)
Re:Steam Engine - Diesel (Score:4, Informative)
Note that I am talking about pure performance gain here, not percieved performance, such as keeping a GUI responsive during long actions - that kind of MT is generally slower than the single threaded alternative, and is fairly easy to keep correct.
Gaining performance via multithreading requires you to seperate out multiple calculations, with minimal dependencies between them. The number of applications that can benefit from this is much smaller than you might think. I doubt very much that we'll see very many applications get a boost from dual/many core processers, and it's not just a matter of "re-writing legacy apps". What we will see is over all system speed increases on multi-threaded OSes.
Re:Steam Engine - Diesel (Score:2)
Re:Steam Engine - Diesel (Score:3, Insightful)
I think this is a foolish thing to doubt. As supercomputing evolved into parallelism the same thing was said; it's too hard, some things can't be done in parallel. Yet solutions have been found for most cases and there is no lack of desire for more parallel capacity today.
Put enough cores in front of a twenty something Carmack wannabe and he'll figur
Re:Steam Engine - Diesel (Score:2, Insightful)
Re:Steam Engine - Diesel (Score:2)
WTF? (Score:5, Funny)
What is this now, Questions for Nerds. Stuff we dont know?
well at least he seems to understand the problems (Score:5, Interesting)
"Problem: Legacy Apps You'd be surprised how many cycles the world's Sun boxes spend running decades-old FORTRAN, COBOL, C, and C++ code in monster legacy apps that work just fine and aren't getting thrown away any time soon. There aren't enough people and time in the world to re-write these suckers, plus it took person-centuries in the first place to make them correct.
Obviously it's not just Sun, I bet every kind of computer you can think of carries its share of this kind of good old code. I guarantee that whoever wrote that code wasn't thinking about threads or concurrency or lock-free algorithms or any of that stuff. So if we're going to get some real CMT juice out of these things, it's going to have to be done automatically down in the infrastructure. I'd think the legacy-language compiler teams have lots of opportunities for innovation in an area where you might not have expected it."
Re:well at least he seems to understand the proble (Score:2)
Well, the Fortran programs have an easy solution---just recompile with a modern compiler designed for these CPU's. Any loop that can
Re:well at least he seems to understand the proble (Score:2)
Please unroll the following loop automatically (not FORTRAN, but simple enough to translate):
Now make the code parallel.
(I realize that this solution could actually be computed at compile-time for any known value of N, and I realize that there is a formula to compute this answer in constant
Re:well at least he seems to understand the proble (Score:2, Informative)
Re:well at least he seems to understand the proble (Score:2)
Re:well at least he seems to understand the proble (Score:2)
Re:well at least he seems to understand the proble (Score:2)
Well, perhaps it's a job for the compiler to make that code thread-aware, at least to some degree. Two consecutive function calls that you (the compiler) know to be independent? Execute them in parallel. A loop running over 10000 independent objects? Split it into k loops, 10000/k objects each.
Of course the compiler has severe limits as to what it can really guess
How is this different from having multiple cores? (Score:2, Offtopic)
...and isn't this the challenge being addressed by DragonFly BSD? [dragonflybsd.org]
Software people use threads already, as long as the VM and OS are up to the task. I don't see why it should matter if some of the threads are implemented in hardware.
Vader vs. Brooks? (Score:3, Funny)
Re:Vader vs. Brooks? (Score:2, Insightful)
Look out! It's Garth Vader!
One Weenie's Perspective (Score:5, Funny)
Not really an issue (Score:3, Insightful)
Question: What needs multiple threads? (Score:2, Interesting)
I really only know the "scientific" programming languages, but most all math specific routines are already written for parallel machines. I'm a bit curious, what else really needs multiple threads? Isn't the benefit of dual-core procs the ability to not have a slow-down when you run two or three apps at a time? Don't games like DOOM III and Half-Life II depend mostly on the GPU (which I'm gu
Re:Question: What needs multiple threads? (Score:5, Insightful)
In games the AI of non-player-characters (-objects) can profit a lot from threading.
But for common apps
Re:Question: What needs multiple threads? (Score:3, Informative)
It's all about the algorithms. Once multi-core chips have been mainstream for a while, all the algorithms out there will start to get converted to take advantage of parallel processing. And there are already algorithms out there that do this... this page [cmu.edu] has a small repository of parallel implement
Re:Question: What needs multiple threads? (Score:3, Insightful)
Re:Question: What needs multiple threads? (Score:3, Interesting)
Thread 1: OS kernel
Thread 2: firewall
Thread 3: GUI
Thread 4: print server
Thread 5-7: various services (update, power, etc)
Thread 8: antivirus
Thread 9: antivirus manager/keep-alive
Thread 10-16: spyware (I said a typical Windows box)
Thread 17+: applications
Yeah, CMT will be handy out of box as long as the OS is aware. I expect it will be wasteful the
Re:Question: What needs multiple threads? (Score:2)
What you propose (not a horrible idea, btw) requires much more than just some threads in the CPU.
Can use, not needs! (Score:2, Interesting)
Remember the old days when people used fancy tricks to implement naturally concurrent solutions as single-threaded programs? The future is going to be just the opposite. Any day now we'll see a rush toward langages with special support for quick, clear, safe parallelism, just like we've seen scripting
Re:Question: What needs multiple threads? (Score:2, Informative)
Actually there is a whole lot to games like DoomIII and HL2 than what can be run on the GPU. First of all, a lot of the graphics-related code is never run on the GPU, it's run on the CPU (for example shadow-processing code), which then passes on the info to the GPU to do the actual rendering.
Secondly multiple core GPUs doesn't make that much sense to me. The nature of graphics processing is completely SIMD (like much o
Re:Question: What needs multiple threads? (Score:2)
Big Hairy Package (Score:5, Funny)
Vivid imagary...
Screw CMT; Time to use wasted CPU (Score:2)
I would be far more interested in taking advantage of all the CPU cycles that run all over at Businesses. THink of how much wasted cycles there are running Screen Saver, or a Word document. By distributing the load amongst the systems, then a large number of things can be done.
Re:Screw CMT; Time to use wasted CPU (Score:3, Interesting)
Condor [wisc.edu].
Programming isn't up to it (Score:5, Interesting)
Current programming languages are insufficiently descriptive to permit compilers to generate usefully multi-threaded code.
Accordingly, multi-threading is currently handled by the programmer; which by and large doesn't happen, because programmers are not used to it.
A lot of applications these days are weakly multi-threaded - Windows apps for example often have one thread for the GUI, another for their main processing work.
This is *weak* multi-threading; because the main work done occurs within a single thread. Strong multi-threading is when the main work is somehow partioned so that it is processed by several threads. This is difficult, because a lot of tasks are inherently essentially serial; stage A must complete before stage B which must complete before stage C.
The main technique I'm aware of for making good use of multi-threading support is that of worker-thread farms. A main thread receives requests for work and farms them out to worker threads. This approach is useful only for a certain subset of problem types, however, and within the processing of *each* worker thread, the work done itself remains essentially serial.
In other words, clock speeds have hit the wall, transistor counts are still rising, the only way to improve performance is to have more CPUs/threads, but programming models don't yet know how to actually *use* multiple CPU/threads.
El problemo!
--
Toby
Re:Programming isn't up to it (Score:2)
So, Sun managed to put an NCR Voyager on a single chip? Uhh... cool?
Re:Programming isn't up to it (Score:5, Interesting)
multi-threaded programming is the predominant programming model on servers. Some tasks, such as web serving, mail serving, and to some degree data-base machines scale almost linearly with the number of processors. All of the first tier, and some of the second tier server manufacturers have been selling 32+-way SMP boxes for years. They work pretty damn well.
Sun is not trying to create a chip to supplant pentiums in desktops. They are not going for the best Doom3 performance. They want to handle SQL transactions, and IMAP requests, and most likely are targetting this at JSP in a big way.
As a user of a slightly aged sun SMP box, I'd rather have those many slow CPUs and the accompanying I/O capability, than a pair of cores that can spin like crazy waiting for memory.
Re:Programming isn't up to it (Score:2)
> to some degree data-base machines scale almost
> linearly with the number of processors. All of the
> first tier, and some of the second tier server
> manufacturers have been selling 32+-way SMP boxes
> for years. They work pretty damn well.
I explicitly described this method of multi-threading in my reply.
I also noted that when the work done by each thread is examined, it is performing serial tasks; e.g. it is internally single-threaded,
Re:Programming isn't up to it (Score:3, Informative)
On single processor systems, when it wants to switch between two threads, it usually executes a context switch - it needs to dump one set of registers to memory, load the other set from memory and change the instruction pointer.
That usually adds up to two seperate memory accesses to different parts of memory. What's more, is that it is not always possible
Re:Programming isn't up to it (Score:3, Informative)
Re:Programming isn't up to it (Score:3, Informative)
Now,
Re:Programming isn't up to it (Score:3, Informative)
It's the only Right Way (TM) to find a problems. Now, I don't recommend reasoning about the code to find typos, but then again, you shouldn't be making typos anyway.
In my experience, problems with multi-threaded code almost never come from a lack of understanding of how to write multi-threaded code.
Most people would disagree. Almost invariably, problems with multithreaded code are the fault of the programmer. Race conditions, dea
Re:Programming isn't up to it (Score:2)
Many problems require the result of operation X to complete operation Y; in other words the algorithms are naturally serial in nature and are not easily amenable to parallelism.
There are a few clever tricks but in some cases making a serial operation parallel gives vastly decreasing performance gains (i.e. two threads = 110% of one thread, four threads = 105% of two threads, etc).
Re:Programming isn't up to it (Score:4, Interesting)
I agree.
However, I believe that Functional programming languages would seem to have the best chance of successfully taking advantage of multiple threads of execution. Google has 100,000+ computers doing this now using functional programming ideas.
As pointed out in other posts, not every problem will benefit from parallelism. With research and time, this might change. Many problems can be represented in both procedural constructs and recursive constructs. The procedural has been considered the most comprehendable and implementable for the past three decades. This may have to change in light of the direction the hardware technology is going.
Re:Programming isn't up to it (Score:2)
Re:Programming isn't up to it (Score:4, Insightful)
"Current programming languages are insufficiently descriptive to permit compilers to generate usefully multi-threaded code."
The portion of importance is:
"insufficiently descriptive"
In C, C++, and Java, you must program with concurrency in mind to obtain any benefit from multiple threads of execution. In a functional programming language, the restrictions placed on the behavior of functions often imply concurrency without the programmer necessarily intending that as the result. If you write a C program without concurrency in mind and want to adapt your solution later to take advantage of multiple threads, you may need to code a completely different solution and also locate a compiler that knows how to take advantage of concurrency. In a functional language, you may only need to get an updated version of your compiler/interpreter. This is why C, C++, and Java are in the "insufficiently descriptive" category and functional programming languages are not.
OLTP systems (Score:3, Informative)
Well, since I work in airline reservations systems, I'll add my $0.02 worth...
Most OLTP systems will benefit from CMT and multi-core processors. We had a test server from AMD about a month before the dual-core Opteron was announced, we did some initial testing and then put it in the production cluster and fired it up. No code changes, no recompile, no drama.
IMHO, the single-user applications, such as games and word processors, will be harder to parallelize.
Alan.
What a totally vague and useless post, yipee! (Score:2, Insightful)
So the observations that there is too much locking in Java's standard api is informative but not on-topic. the fact that the standard solution is to use a completely new class [e.g. StringBuilder] is why I laughed at my college profs when they were trying to sell their Java courses by saying "and Java is well supported with over 900
You might want to go back to school... (Score:5, Insightful)
The BEST a single core multi-thread design can hope for is the performance of a single core single thread design...
I'm sorry but that turns out not to be the case.
When you have a system that is running lots of different threads simultaneously the amount of time that it takes to do a context switch from one thread to another becomes an issue. In the real world, threads often do things like I/O which cause them to block or they wait on a lock. If you can do a fast context switch you get back the time that you would have wasted saving registers off to RAM and pulling back another set. Faster thread switching means that your multi-thread single core now runs its total load (all of the threads) faster than a single core single thread design. Also, things like microkernels become a lot more feasible (microkernels are notorious for being slow because context switches are slow).
When you have looked beyond your desktop machine maybe you'll have earned the right to sneer at your professors. I don't think you're there yet.
Re:What a totally vague and useless post, yipee! (Score:2)
So if you make a shoddy ALU that stalls a lot another register set can get you better performance overall [but not for individual threads] and if you make a good ALU your extra register set in hardware buys you VERY LITTLE.
A dual core cpu is something else. that'
We all are (Score:2)
If one of your favorite applications happen to be multithreaded then that's gravy.
But you'll benefit anyway. If you bring up your process list you'll see that you have probably at least 10 processes. These will now be able to run independently.
Also, the windows kernel itself can benefit from hardware threads.
Re:We all are (Score:2)
Think about it this way. You have one car that can carry you and your buddies to work at 50mph and two cars that can take you and your buddies to work at 30mph.
Sure the two cars let you do independent things but when you're working on one task [getting to work] you're not ahead.
In a video game context for instance, you do have mul
Re:We all are (Score:2)
Do you disagree with that?
I disagree (Score:2)
But you're not, you never are working on only 1 task.
Look at the threads running on a PC and its hundreds, you have file cache threads, communications threads, all kinds of stuff running.
A whole convoy of cars all sitting in one lane waiting for the car in front.
You keep the speed limit the same, make the highway 8 lane and 8 times the cars can pass through.
Also you would save the thr
What doesn't scale (and what does) (Score:2)
The latter can scale on multi-processors, and mostly do. Much of our performa
Need a breakthrough in hiding concurrency (Score:3, Insightful)
One of UNIX's most important features is the pipe-and-filter model, and one of the really great things about it is that it lets you build scripts that can automatically take advantage of coarse-grained concurrency. Even on a single-CPU system, a pipeline lets you stream computation and I/O where otherwise you'd be running in lockstep alternating I/O and code.
That's where the big breakthroughs are needed: mechanisms to let you hide concurrency in a lower layer. Pipelines are great for coarse-grained parallelism, for example, but the kind of fine grain you need for Niagara demands a better design, or the parallelism needs to be shoved down to a deeper level. Intel's IA64 is kind of a lower level approach to the same thing where the compiler and CPU are supposed to find parallelism that the programmer doesn't explicitly specify, but it suffers from the typical Intel kitchen-sink approach to instruction set design.
Hdw multi-thread vs multi-CPU (Score:2)
The bottlenecks (Score:4, Interesting)
I'll misquote Fred Weigel and suggest that the next problem is branching: Samba code seems to generate 5 instructions between branches, so suspending the process and running something else intil the branch target is in I-cache seems like A Good Thing (;-)).
Methinks Samba would really enjoy a CMT processor.
--dave
dead end (Score:3, Insightful)
But the future of high-end computing, both in business and in science, will not look like that. Networks of cheap computing nodes scale better and more cost-effectively. Many manufacturers have already gone over to that for their high-end designs. That's where the real software challenges are, but they are being addressed.
Processors with lots of thread parallelism will probably be useful in some niche applications, but they will not become a staple of high-end computing.
How to make code run fast? (Score:3, Interesting)
So if you have a function that say does 10 additions and 10 moves you would first figure out if any of them needed to be done before or after each other. Then see which ones don't matter. Then write the function to do as many at once as possible.
It really doesn't matter for anyone other than the compiler writers. Those guys will write the compiler to do this kind of assembly level optimization for you. The trick is writing a high level language, or modifying an existing one, so the compiler can tell which things must be executed in order and which can be executed side by side.
My CPU left me, and the Flatscreen died.... (Score:2)
* crickets *
Time to hand in my nerd badge I guess, and slink off into the sunset.
Seriously, though - thanks for clarifying the meaning of CMT in the blurb. A big step forward from the usual Slashdot blurb.
What is the problem here? (Score:2)
It isn't. And it isn't just scientific data chugging which would benefit from increased availability of actual concurrent processing in typical desktop computers; there are currently many of these PCs that already to things that can be paralellized.
For instance image processing. For many kinds of imag
Compilers and "Events Model" (Score:2)
With this model it is kind of hard to use the multithreading processors. Of course after the user has triggered an action then the program could make use of the threading capability to improve its performance.
Next comes the problem of
Re:Compilers and "Events Model" (Score:2)
Another way to use multithreading could be from the Operating System, so the programs [that do not require] multithreading wont have to deal with it BUT the operating system would use the multithreading capacities to schedule the processes execution... in this way we may get [AT LAST] a [REAL] multiprocess OS (and not the illusio
Sun needs more raw performance (Score:2)
Old news for IBM, this is just Sun catching up (Score:2, Interesting)
New job - new tools (Score:2)
Traditional languages that have had threads bolted on like C/C++ make threading more challenging than it needs to be. Java, as long as you understand the principles of concurrency, makes it a breeze. I would be interested to see weather a well coded JVM / JIT could outperform traditional languages on these new CPUs - especially if you could dedicate a couple of the hardware threads to JIT, and GC threads.
The author doesn't understand Java class locking (Score:3, Informative)
The standard APIs that came with the first few versions of Java were thread safe; some might say fanatically, obsessively, thread-safe. Stories abound of I/O calls that plunge down through six layers of stack, with each layer posting a mutex on the way; and venerable standbys like StringBuffer and Vector are mutexed-to-the-max. That means if your app is running on next year's hot chip with a couple of dozen threads, if you've got a routine that's doing a lot of string-appending or vector-loading, only one thread is gonna be in there at a time.
Classes such as StringBuffer and Vector are locked (synchronized) on a per-object basis. As long as you aren't trying to access the same object from different threads you won't block. And if you are trying to access the same object from different threads you will be happy that they were thread-safe!
The performance problems of having these classes being obsessive about thread safety do not result from the locking forcing singlethreadedness. The performance problem stem from the cost of locking objects.
I didn't see garbage collection in his list (Score:3, Interesting)
Why the future of SMT is bleak (Score:5, Informative)
Re:Why the future of SMT is bleak (Score:3, Insightful)
I didn't read most of the princeton paper... but you're arguing that caches need to be big to get
Re:Windows Articles, Slashdot and Pragmatism (Score:2)
I'm sure you didn't mean to but your post ended up showing up as the first post in an Article about CMT [slashdot.org]. What's really wierd is that it showed up after a bunch of other posts...
Re:EPIC? (Score:3, Interesting)