Hello,
I have been playing with time in m5 syscall emulation mode and had a couple of
issues:
First of all I believe there is a bug in the times() syscall implementation
(sim/syscall_emul.hh). The current clocks value passed to the userland is:
int64_t clocks = curTick * OS::M5_SC_CLK_TCK / SimClock::Int::s;
This evaluates to a wrong expression. Now, according to the man page all the
tms buffer values are supposed to be in clock ticks. Thus a more appropriate
expression for it would be:
int64_t clocks = tc->getCpuPtr()->tickToCycles(curTick);
Secondly, I have implemented the nanosleep() system call. I believe that the
appropriate way to do this would be suspending (tc->suspend()) the
ThreadContext and re-activating (tc->activate(delay)) after the sleep duration
(please correct me if I am mistaken). This however led to a peculiar behaviour
with O3 in SMT mode:
1. in FullO3CPU<Impl>::suspendContext (cpu.cc) the CPU _status is set to Idle,
regardless whether there are other running contexts in the CPU. Thus a thread
sleeping leads to all the other SMT threads sleeping.
2. in FullO3CPU<Impl>::activateContext (cpu.cc) we schedule a tick event after
the delay parameter passed, effectively overwriting CPU's tickEvent and moving
all threads of the processor tick(delay) ticks forward. Is this the intended
behaviour or is it a bug? Clearly in my case it is not helpful since the point
of getting a thread to sleep relative to the other threads' time.
Thank you,
Ioannis
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