executing threads at the same time
in [CSharp]
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From: Tony Johansson on 10 May 2010 05:13 Hi! I will be sure that I have understood this correctly. Assume you have a computer with two kernels and I run two additional threads that run the same method can then these two threads be executing fysically the exact same instruction at the exact same time. As fas as I understand this I mean you would still use the mechanism of pre-emptive multitasking between these two threads. I mean that you do have two threads executing at the same time but you still use the mechanism of pre-emptive multitasking between them so at any singe moment in time only one of these two threads is really executing an instaruction while the other is waiting to get cpu time to continue executing. //Tony
From: Rick Lones on 10 May 2010 08:27 Tony Johansson wrote: > Hi! > > I will be sure that I have understood this correctly. > Assume you have a computer with two kernels and I run two additional threads > that run the same method > can then these two threads be executing fysically the exact same instruction > at the exact same time. Assuming you mean two CPU cores and not two kernels, then the answer is yes. If you have two CPUs, then each is capable of independently running a given instruction stream simultaneously with whatever the other one is doing. So in principle they could be executing in lockstep different invocations of the same instruction stream, although this would be highly unlikely. (If that's what you really mean to ask here.) > As fas as I understand this I mean you would still use the mechanism of > pre-emptive multitasking between these two threads. Yes, always. > I mean that you do have two threads executing at the same time but you still > use the mechanism of pre-emptive multitasking between them so at any singe > moment in time only one of these two threads is really executing an > instaruction while the other is waiting to get cpu time to continue > executing. Well, yes. But now you are back to talking as if there is only one CPU core. With one CPU you get multi-tasking. With multiple CPUs you get concurrent execution where EACH core is being muli-tasked by the operating system. HTH, -rick-
From: Arne Vajhøj on 10 May 2010 18:14
On 10-05-2010 05:13, Tony Johansson wrote: > I will be sure that I have understood this correctly. > Assume you have a computer with two kernels and I run two additional threads > that run the same method > can then these two threads be executing fysically the exact same instruction > at the exact same time. > > As fas as I understand this I mean you would still use the mechanism of > pre-emptive multitasking between these two threads. > > I mean that you do have two threads executing at the same time but you still > use the mechanism of pre-emptive multitasking between them so at any singe > moment in time only one of these two threads is really executing an > instaruction while the other is waiting to get cpu time to continue > executing. If you have N execution units (approx. equals to cores for modern desktop CPU's), then N thread can execute in parallel on their own execution unit. Preemptive multitasking does not mean just one thread executing. It means that threads get removed from the CPU by the OS. Arne |