Hi Abishek,
A single MSHR can keep track of more than one requests for a given cache
line. If you set tgts_per_mshr to 1, then the MSHR will only be able to
keep track of a single request for any given cache line. But it can
still service requests to other cache lines by allocating more MSHRs.
If you want the cache to block on a single request you will need to
limit both the number of MSHRs and tgts_per_mshr to 1.
I hope this helps.
Nikos
On 25/03/2019 19:03, Abhishek Singh wrote:
> Hello Everyone,
>
> I am trying to simulate D-cache with one target per mshr, I tried
> changing the parameter "tgts_per_mshr" defined in
> "configs/common/Caches.py" to 1, it does not work.
>
> This is because when we allocate target for existing MSHR, we always
> check the "tgts_per_mshr" parameter after allocating the second target
> and blocks the requests coming from LSQ.
>
> I tried copying the blocking target code to an allocateMissBuffer
> function defined and declared in "src/mem/cache/base.hh" as:
>
>
> *_BEFORE_*:
>
> MSHR *allocateMissBuffer(PacketPtr pkt, Tick time, bool sched_send = true)
>
> {
>
> MSHR *mshr = mshrQueue.allocate(pkt->getBlockAddr(blkSize), blkSize,
>
> pkt, time, order++,
>
> allocOnFill(pkt->cmd));
>
>
> if (mshrQueue.isFull()) {
>
> setBlocked((BlockedCause)MSHRQueue_MSHRs);
>
> }
>
>
> if (sched_send) {
>
> // schedule the send
>
> schedMemSideSendEvent(time);
>
> }
>
>
> return mshr;
>
> }
>
>
>
> *_AFTER:_*
>
>
>
> MSHR *allocateMissBuffer(PacketPtr pkt, Tick time, bool sched_send = true)
>
> {
>
> MSHR *mshr = mshrQueue.allocate(pkt->getBlockAddr(blkSize), blkSize,
>
> pkt, time, order++,
>
> allocOnFill(pkt->cmd));
>
>
> if (mshrQueue.isFull()) {
>
> setBlocked((BlockedCause)MSHRQueue_MSHRs);
>
> }
>
>
> *if (mshr->getNumTargets() == numTarget) {*
>
> **
>
> *//cout << "Blocked: " << name() << endl;*
>
> *noTargetMSHR = mshr;*
>
> *setBlocked(Blocked_NoTargets);*
>
> *}*
>
> *
> *
>
> if (sched_send) {
>
> // schedule the send
>
> schedMemSideSendEvent(time);
>
> }
>
>
> return mshr;
>
> }
>
>
> I also change the "tgts_per_mshr" defined in "configs/common/Caches.py"
> to 1.
>
> But simulation goes into an infinite loop and does not end.
>
> Does anyone have the technique to create Blocking caches with 1
> target per MSHR entry?
>
>
>
> Best regards,
>
> Abhishek
>
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