No, you're just quote-mining stuff and taking statements well beyond their original context. You really think SGI developers don't have access to their own hardware, for instance?Well, according to Linux devs, for instance, Ted Tso, you are wrong.
Of course the worst case remote memory latency on a big CC-NUMA will be much higher than for local memory. That's the entire point. The alternative, after all, is not SMP but rather USMA (uniformly slow memory access). And yes, in order to run efficiently on a big CC-NUMA machine you need an OS kernel that has been designed with this in mind (such as Linux) as well as applications that are very careful wrt non-local memory accesses. The latter point ruling out most applications including RDBMS'es which is why you don't see 4096-way DB servers anywhere.And, as I have said, the big Linux 4.096 core HPC systems have terrible latency
Of course, an OS that works well on machines with a high NUMA factor can work just fine on machines with a low NUMA factor or none at all, Linux being a nice example of this.
So a workload that gets only 75% efficiency on 24 cores/4S is slow when running on a system with cache coherency provided by a virtualization layer rather than hw and connected with IB is somehow NOT bleeting obvious? Sheesh (woot, we're going in circles!!), and it might look like a shared memory, but it isnt:
"I tried running a nicely parallel shared memory workload (75% efficiency on 24 cores in a 4 socket opteron box) on a 64 core ScaleMP box with 8 2-socket boards linked by infiniband. Result: horrible. It might look like a shared memory, but access to off-board bits has huge latency."
No, I'm not. Sorry if I didn't include my by now routine SMP != CC-NUMA point; it's difficult to see whether you've actually gotten that or not since you continue to talk about "big SMP".Ok, so you claim that there are big SMP Linux servers on the market.
Did you read the paragraph you're answering to? In case you didn't, here an excerpt again: "HW is available (except for SGI, you probably can't get a support contract for running Linux on it, but for kernel development that is of course irrelevant)." Duh.Fine. Please show me links then. I am not talking about a prototype as Big Tux HP Superdome or experimental POWER7, I am talking about SMP servers for sale, with supported 64 cpus or so. Where are those links?
Well, again with the caveat that all big machines are CC-NUMA, not SMP, those developers who are working on scalability issues have access to big machines to benchmark their work. I've recently even given a couple of prominent examples, the SGI developers who have worked on scalability issues relevant for their customers, and the VFS scalability work.But which Linux devs has access to those big SMP servers that are for sale?
Well, again with the caveat that all big machines are CC-NUMA, not SMP, there's plenty of big machines for sale by IBM, HP, Fujitsu, SGI, and probably others as well.Where are those SMP servers, by the way? Who sell them?
Obviously, I'm not going to give a blanket agreement with something "everyone else" says or may say in the future. If I feel a need to publicly agree with someone else, I'll explicitly says so. Don't assume I agree with something I haven't written.You and everyone else
What the heck is this statement even supposed to mean? If one takes the usual definitions for SMP and HPC, it seems like an apples to oranges comparison., claim: that Linux does SMP as easily as HPC.
No, they are CC-NUMA machines. I've never claimed that they are "SMP servers".And the HPC Altix servers, are in fact SMP servers.
My claims? Yes. Some strawman claim you came up with all by yourself? Obviously not, since the claims were designed by yourself to be false.Does you claim hold water?
It says that you're a proper frothing-at-the-mouth Solaris fanboy, desperately grasping at any straws you can find in order to make Solaris look good. And since you don't have a solid grasp of the issues you're talking about, much lulz ensues.There is something called Occams razor. What does it say?