Dear Jason, thank you for your answer. It gives me a hint how does gem5 work, but I am unsure about the details. Is there any document which explains this?
To be concrete, if there are 4 cores and 4 threads, within once cycle, each of them executes tick() on their own? Best regards, Jasmin On Tue, Jan 17, 2017 at 3:59 PM, Jason Lowe-Power <[email protected]> wrote: > Hi Jasmin, > > gem5 is an event-driven simulator. So, when there are multiple objects > (e.g., multiple CPU cores, or caches, or memory controllers, etc.) all of > these objects can execute in parallel in simulated time (or guest time to > use virtual machine nomenclature). The CPU models don't necessarily execute > one instruction at a time. Instead they are simulated at the clock-cycle > level. Each action which takes place at some clock-cycle boundary is > scheduled and then executed as an event in the event-driven simulation. > > gem5 is mostly single threaded. All of the CPUs in your simulated system, > and all of the other objects like caches, etc. are simulated in a single > host thread. There are a few places where this isn't true, but it's unusual > to run gem5 with parallel event queues. > > Hopefully this helps explain things. Let us know if you have more > questions. > > Cheers, > Jason > > On Tue, Jan 17, 2017 at 4:29 AM Jasmin Jahic <[email protected]> > wrote: > >> Hello, >> >> I have one question regarding multi threading in gem5, in full system >> mode. Since gem5 is seen as one process at host OS, how does gem5 actually >> emulate multiple threads/processes? Let's say that we have 4 core CPU and >> several processes and threads. Are these run in parallel really (one >> instruction of this thread, then one instruction of another thread...?) or >> there is some more complex mechanism? >> >> Is there perhaps a presentation or document which explains this? >> >> Best regards, >> Jasmin JAHIC >> _______________________________________________ >> gem5-users mailing list >> [email protected] >> http://m5sim.org/cgi-bin/mailman/listinfo/gem5-users > > -- > > Jason > > _______________________________________________ > gem5-users mailing list > [email protected] > http://m5sim.org/cgi-bin/mailman/listinfo/gem5-users >
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