Offhand it seems like takeOverFrom() should work... what other errors
do you get when you use it?
On 11/12/07, Nicolas Zea <[EMAIL PROTECTED]> wrote:
> I'm trying to implement a version of context switching that involves
> storing the context of a cpu from one point in time in a hardware
> storage, then at a later point in time reloading that context,
> possibly on a different cpu. Previously I had done something similar,
> where the benchmark on core 1 was restarted on core 2. My method for
> this was backing up the AlphaLiveProcess ptr until I want to resume
> that process. At that point I'd start a drain event, clear the
> registers, attach the process to the cpu and replace the process'
> thread context with that from the cpu, call startup on the process,
> then resume the cpu.
>
> The following code did this (after the drain completed):
>
> // reset the registers in cpu (to 0)
> for(int i=0; i<thecpu->regFile.numPhysicalIntRegs; i++){
> thecpu->regFile.intRegFile[i] = 0;
> }
> for(int i=0; i<thecpu->regFile.numPhysicalFloatRegs; i++){
> thecpu->regFile.floatRegFile[i].d = 0;
> }
> for(int i=0; i<AlphaSimpleImpl::MaxThreads; i++){
> thecpu->regFile.miscRegs[i].clear();
> }
>
> if(pkt->servo_proc->pTable != NULL){
> // reset the page table
> delete myproc->pTable;
> myproc->pTable = new PageTable(myproc->system);
> }
>
> // make sure to reset the translating port
> if(((AlphaTC<AlphaSimpleImpl>
> *)(thecpu->threadContexts[0]))->thread-
> >port != NULL){
> // reset the translating port so it uses the new page
> table
> delete ((AlphaTC<AlphaSimpleImpl>
> *)(thecpu->threadContexts[0]))-
> >thread->port;
> ((AlphaTC<AlphaSimpleImpl>
> *)(thecpu->threadContexts[0]))->thread-
> >port = NULL;
> }
>
> ((AlphaTC<AlphaSimpleImpl>
> *)(thecpu->threadContexts[0]))->thread-
> >process = pkt->servo_proc; // attach the process
> thecpu->registerThreadContexts(); // register the
> process
>
> myproc->replaceThreadContext(thecpu->threadContexts[0], 0);
> //
> attach the thread to the process
>
> myproc->startup(); // perform the initial write of
> program data into
> memory, and reset the cpu state (PC, NPC, SP, etc.)
>
> What I'd like do now is resume from the exact point the process was
> executing before. I've backed up the register values, as well as PC
> and NPC in an data container. I assumed that I could simply use the
> same steps, except instead of using myproc->startup() to set the PC,
> I'd set it manually (thecpu->setPC()). Additionally, I wouldn't reset
> the page table, as it would be reused.
>
> This doesn't appear to work though, as the PC does not appear to get
> reloaded from commit.PC (which is what I gather setPC modifies),
> unless I call fetch.takeOverFrom(), at which point other errors in the
> different pipeline stages arise. Does anyone have some advice on the
> steps required to do this kind of contextual switch?
>
> For information, I'm running this on m5 2.0b2 in ALPHA_SE mode, and
> all the processes are independent single-threaded applications.
>
> -Nick
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>
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