On Thu, 9 Sep 2004, Ronan Cunniffe wrote:
> Yes, but not much! :-)
Hmm, well that depends too on your POV. Yours is very much from the
sci-comp perspective ;)
> For anything that even remotely resembles the above snippet, the
> CPU is going to be dead-accurate in branch prediction, meaning
> effectively no branches, probably no bubbles at all if either
> function() or inputs[i] are anyway complicated, and a single thread
> can saturate the FPU resources of the chip.
> Eh, what's a server workload?
Multiple varied tasks, possibly a fair amount of IO.
Indeed, desktop is a bit like that too.
> Does yours look like this (note the runtime...) ?
>> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
> 32541 user 27 2 1760 532 1492 R 51.7 0.1 9754:24 zazp1.x
> 32545 user 27 2 1760 532 1492 R 49.7 0.1 9754:40 zazp2.x
No it doesnt. Nor do most people's ;)
> HT would only be a good idea if there was constant and massive
> shuffling of data in from disk, and this could be handled
> predictively by a helper thread. This assumes that you're writing
> your own code, which is rarely true. Most science apps are
> explicitly written to a 1-thread-per-node model, with any
> parallelism achieved by using MPI.
Right, but most people's workloads are *not* like that. Hence exactly
why Intel added HT. ;) For most server/desktop uses, HT likely *is* a
Course, you need to benchmark your own uses to find out.
Paul Jakma paul at clubi.iepaul at jakma.org Key ID: 64A2FF6A
A writer who guesses his way to the truth and dispels it with a
tempest of words.
-- Ambrose Bierce, "The Devil's Dictionary"
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