changeset 2694770a30d4 in /z/repo/gem5
details: http://repo.gem5.org/gem5?cmd=changeset;node=2694770a30d4
description:
mem: Make LL/SC locks fine grained
The current implementation in gem5 just keeps a list of locks per
cacheline.
Due to this, a store to a non-overlapping portion of the cacheline can
cause an
LL/SC pair to fail. This patch simply adds an address range to the lock
structure, so that the lock is only invalidated if the store overlaps
the lock
range.
diffstat:
src/mem/cache/blk.hh | 41 ++++++++++++++++++++++++++++++++++++-----
1 files changed, 36 insertions(+), 5 deletions(-)
diffs (76 lines):
diff -r 0694ba392248 -r 2694770a30d4 src/mem/cache/blk.hh
--- a/src/mem/cache/blk.hh Tue Jan 08 08:54:06 2013 -0500
+++ b/src/mem/cache/blk.hh Tue Jan 08 08:54:07 2013 -0500
@@ -127,15 +127,30 @@
class Lock {
public:
int contextId; // locking context
+ Addr lowAddr; // low address of lock range
+ Addr highAddr; // high address of lock range
// check for matching execution context
bool matchesContext(Request *req)
{
- return (contextId == req->contextId());
+ Addr req_low = req->getPaddr();
+ Addr req_high = req_low + req->getSize() -1;
+ return (contextId == req->contextId()) &&
+ (req_low >= lowAddr) && (req_high <= highAddr);
+ }
+
+ bool overlapping(Request *req)
+ {
+ Addr req_low = req->getPaddr();
+ Addr req_high = req_low + req->getSize() - 1;
+
+ return (req_low <= highAddr) && (req_high >= lowAddr);
}
Lock(Request *req)
- : contextId(req->contextId())
+ : contextId(req->contextId()),
+ lowAddr(req->getPaddr()),
+ highAddr(lowAddr + req->getSize() - 1)
{
}
};
@@ -255,7 +270,23 @@
* Clear the list of valid load locks. Should be called whenever
* block is written to or invalidated.
*/
- void clearLoadLocks() { lockList.clear(); }
+ void clearLoadLocks(Request *req = NULL)
+ {
+ if (!req) {
+ // No request, invaldate all locks to this line
+ lockList.clear();
+ } else {
+ // Only invalidate locks that overlap with this request
+ std::list<Lock>::iterator lock_itr = lockList.begin();
+ while (lock_itr != lockList.end()) {
+ if (lock_itr->overlapping(req)) {
+ lock_itr = lockList.erase(lock_itr);
+ } else {
+ ++lock_itr;
+ }
+ }
+ }
+ }
/**
* Handle interaction of load-locked operations and stores.
@@ -283,12 +314,12 @@
}
req->setExtraData(success ? 1 : 0);
- clearLoadLocks();
+ clearLoadLocks(req);
return success;
} else {
// for *all* stores (conditional or otherwise) we have to
// clear the list of load-locks as they're all invalid now.
- clearLoadLocks();
+ clearLoadLocks(req);
return true;
}
}
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