On Tue, 3 Jan 2012, Mahmood Naderan wrote:
refCount is just counting the number of times that block has been
referenced. The lru policy is maintained without making use of refCount.
i can not understand why....
Doesn't "refCount is just counting the number of times that block has
been referenced" represent a Most Recently Used (or Lease Recently
Used) block?
No.
Read the function accessBlock() in lru.cc
From my understandings,
1) a block is found based on set and tag
BlkType *blk = sets[set].findBlk(tag);
2) If the block is found, it is placed on the MRU position:
sets[set].moveToHead(blk);
This line is enforcing the LRU discipline.
3) The next 'if" statement is about timing.
4) incrementing the refCount which shows this block has been accessed
blk->refCount += 1;
5) the block is returned to caller (cache_impl.hh::access())
So where is replacement?
The function accessBlock() does not need to perform any replacement.
--
Nilay
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