Does this apply to single processor machines with dual cores or just multiple processors?
Interesting point, but from the OS kernel's point-of-view a single-processor, dual-core machine looks exactly like a machine with two processors. So it runs the same code to support SMP whether we're talking single-processor dual-core or multiple processors.
IOW, if there is a performance difference, I would expect it to show up exactly the same in both FreeBSD and Linux (as well as any other OS that supports SMP).
Don't dual core CPUs share components (cache maybe?) that an aware OS can exploit for performance improvements?
The same way an HT CPU shows up as 2 CPUs (with disasterous effects) unless the OS is away and can properly exploit it?
Some dual cores share L2/3 cache, but not all. Another important factors are the shared connections to external world, such as memory. So I presume inter-CPU communication is faster, but external communication can be slower.
That aside, HT is a hack which should not be compared to dual core systems at all. In fact, "dual core processor" is a rather silly marketing term, because it means "two processors on one piece of silicon". In other words, you could interpret the phrase "dual-core CPU" as "a CPU th
The only comparison I was trying to draw to Hyper Transport is that it requires OS awareness to appear as anything different than 2 processors. The fallout of the OS getting this wrong is very different though, with one possibly tanking performance, and the other simply not running as optimally as possible.
Dual Core (Score:0, Interesting)
Re: (Score:3, Interesting)
Does this apply to single processor machines with dual cores or just multiple processors?
Interesting point, but from the OS kernel's point-of-view a single-processor, dual-core machine looks exactly like a machine with two processors. So it runs the same code to support SMP whether we're talking single-processor dual-core or multiple processors.
IOW, if there is a performance difference, I would expect it to show up exactly the same in both FreeBSD and Linux (as well as any other OS that supports SMP).
Re: (Score:1)
The same way an HT CPU shows up as 2 CPUs (with disasterous effects) unless the OS is away and can properly exploit it?
Re: (Score:3, Informative)
Don't dual core CPUs share components (cache maybe?) that an aware OS can exploit for performance improvements?
The same way an HT CPU shows up as 2 CPUs (with disasterous effects) unless the OS is away and can properly exploit it?
Some dual cores share L2/3 cache, but not all. Another important factors are the shared connections to external world, such as memory. So I presume inter-CPU communication is faster, but external communication can be slower.
That aside, HT is a hack which should not be compared to dual core systems at all. In fact, "dual core processor" is a rather silly marketing term, because it means "two processors on one piece of silicon". In other words, you could interpret the phrase "dual-core CPU" as "a CPU th
Re:Dual Core (Score:0)