Hi Olumide, This sounds like a potential bug, though I'm a bit surprised this hasn't been found before. I assume this is happening when you're trying to take a checkpoint since it's occurring during the drain state.
Could you make an issue on the gem5 github issue page? https://github.com/gem5/gem5/issues Thanks! Jason On Mon, Jul 28, 2025 at 4:50 PM Olumide via gem5-dev <gem5-dev@gem5.org> wrote: > Hi- > > I'm repeatedly encountering situations where the MemCtrl stops > scheduling requests even though mem_intr->writeQueueSize is not zero. > > Unfortunately I can neither reproduce it in a MWE or by capturing and > playing back a packet sequence. (As a last resort I may resort to time > travel debug capture with the rr utility.) > > The problem: > In my simulations the path of execution often ends up on line 964 of > mem_ctrl.cc > https://github.com/gem5/gem5/blob/stable/src/mem/mem_ctrl.cc#L964 > > where no more events are scheduled even though > > (gdb) p mem_intr->writeQueueSize > $1 = 15 > > And > > (gdb) call drainState() > $2 = gem5::DrainState::Running > > (gdb) p writeLowThreshold > $3 = 32 > > (gdb) p mem_intr->writeQueueSize > writeLowThreshold > $4 = false > > (gdb) p mem_intr->readQueueSize > $5 = 0 > > (gdb) p mem_intr->busState > $6 = gem5::memory::qos::MemCtrl::READ > > I suspect the culprit is line 1127 of mem_ctrl.cc > https://github.com/gem5/gem5/blob/stable/src/mem/mem_ctrl.cc#L1127 > > The test: > > (below_threshold && drainState() != DrainState::Draining) > > returns true and switches the next bus state to READ even through > mem_intr->readQueueSize == 0. > > When I explicitly force > > mem_intr->busStateNext = MemCtrl::WRITE > > MemCtrl processes one write message but sets the next bus state to > MemCtrl::READ. As such I've had to repeatedly force the next state to > MemCtrl::WRITE until mem_intr->writeQueueSize == 0. > > Please advise. > > Regards, > > - Olumide > _______________________________________________ > gem5-dev mailing list -- gem5-dev@gem5.org > To unsubscribe send an email to gem5-dev-le...@gem5.org >
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