mem-ruby: add TBEStorage structure
The TBEStorage is used to track the resources consumed by the TBETable,
i.e. the number of available TBE slots.
structure(TBEStorage, external ="yes") {
int size();
int capacity();
int reserved();
int slotsAvailable();
bool areNSlotsAvailable(int n);
void incrementReserved();
void decrementReserved();
int addEntryToNewSlot();
void addEntryToSlot(int slot);
void removeEntryFromSlot(int slot);
}
TBEStorage resource tracking has two main differences from TBETable:
1) Allows slot reservation. This is useful to implement protocols that
employ retry/credit messages instead of stall when the controller runs
out of TBEs to accept new request.
2) Can also assign multiple entries to the same slot. This is useful to
more easily model cases where multiple transactions share the same TBE
resource (i.e. the slot).
E.g: a request that triggers a replacement in a system without
dedicated WB/Eviction buffer; both transactions can can have separate
logical TBEs associated to the same slot.
The motivation for having a separate structures for tracking TBEs
availability are twofold:
- Keeps TBETable simple and without the additional overhead for
protocols that do not need these additional features.
- Having two separate transactions sharing the same TBE resource using
the current TBETable would be cumbersome since the TBETable is indexed
by the transaction address.
Change-Id: I64106d50068320bc925243732ef8ff9ef0b6c4bf
Signed-off-by: Tiago Mück <tiago.muck@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/41157
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
4 files changed
