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38 #include "mem/stack_dist_calc.hh"
40 #include "base/chunk_generator.hh"
41 #include "base/intmath.hh"
42 #include "base/trace.hh"
43 #include "debug/StackDist.hh"
45 StackDistCalc::StackDistCalc(bool verify_stack
)
47 verifyStack(verify_stack
)
49 // Instantiate a new root and leaf layer
50 // Map type variable, representing a layer in the tree
51 IndexNodeMap tree_level
;
53 // Initialize tree count for leaves
54 nextIndex
.push_back(0);
56 // Add the initial leaf layer to the tree
57 tree
.push_back(tree_level
);
59 // Create a root node. Node type variable in the topmost layer
60 Node
* root_node
= new Node();
62 // Initialize tree count for root
63 nextIndex
.push_back(1);
65 // Add the empty root layer to the tree
66 tree
.push_back(tree_level
);
68 // Add the initial root to the tree
69 tree
[1][root_node
->nodeIndex
] = root_node
;
72 StackDistCalc::~StackDistCalc()
74 // Walk through each layer and destroy the nodes
75 for (auto& layer
: tree
) {
76 for (auto& index_node
: layer
) {
77 // each map entry contains an index and a node
78 delete index_node
.second
;
80 // Clear each layer in the tree
93 // The updateSum method is a recursive function which updates
94 // the node sums till the root. It also deletes the nodes that
95 // are not used anymore.
97 StackDistCalc::updateSum(Node
* node
, bool from_left
,
98 uint64_t sum_from_below
, uint64_t level
,
99 uint64_t stack_dist
, bool discard_node
)
103 // Make a copy of the node variables and work on them
104 // as a node may be deleted by this function
105 uint64_t node_sum_l
= node
->sumLeft
;
106 uint64_t node_sum_r
= node
->sumRight
;
107 bool node_left
= node
->isLeftNode
;
108 bool node_discard_left
= node
->discardLeft
;
109 bool node_discard_right
= node
->discardRight
;
110 uint64_t node_n_index
= node
->nodeIndex
;
111 Node
* node_parent_ptr
= node
->parent
;
115 // This sanity check makes sure that the left_sum and
116 // right_sum of the node is not greater than the
117 // maximum possible value given by the leaves below it
118 // for example a node in layer 3 (tree[3]) can at most
119 // have 8 leaves (4 to the left and 4 to the right)
120 // thus left_sum and right_sum should be <= 4
121 panic_if(node_sum_l
> (1 << (level
- 1)),
122 "Error in sum left of level %ul, node index %ull, "
123 "Sum = %ull \n", level
, node_n_index
, node_sum_l
);
125 panic_if(node_sum_r
> (1 << (level
- 1)),
126 "Error in sum right of level %ul, node index %ull, "
127 "Sum = %ull \n", level
, node_n_index
, node_sum_r
);
130 // Update the left sum or the right sum depending on the
131 // from_left flag. Variable stack_dist is updated only
132 // when arriving from Left.
135 node_sum_l
= sum_from_below
;
136 stack_dist
+= node_sum_r
;
139 node_sum_r
= sum_from_below
;
142 // sum_from_below == 0 can be a leaf discard operation
143 if (discard_node
&& !sum_from_below
) {
145 node_discard_left
= true;
147 node_discard_right
= true;
150 // Update the node variables with new values
151 node
->nodeIndex
= node_n_index
;
152 node
->sumLeft
= node_sum_l
;
153 node
->sumRight
= node_sum_r
;
154 node
->isLeftNode
= node_left
;
155 node
->discardLeft
= node_discard_left
;
156 node
->discardRight
= node_discard_right
;
158 // Delete the node if it is not required anymore
159 if (node_discard_left
&& node_discard_right
&&
160 discard_node
&& node_parent_ptr
&& !sum_from_below
) {
162 tree
[level
].erase(node_n_index
);
165 // propogate discard_node as false upwards if the
166 // above conditions are not met.
167 discard_node
= false;
170 // Recursively call the updateSum operation till the
171 // root node is reached
172 if (node_parent_ptr
) {
173 stack_dist
= updateSum(node_parent_ptr
, node_left
,
174 node_sum_l
+ node_sum_r
,
175 level
, stack_dist
, discard_node
);
181 // This function is called by the calcStackDistAndUpdate function
182 // If is_new_leaf is true then a new leaf is added otherwise a leaf
183 // removed from the tree. In both cases the tree is updated using
184 // the updateSum operation.
186 StackDistCalc::updateSumsLeavesToRoot(Node
* node
, bool is_new_leaf
)
189 uint64_t stack_dist
= 0;
193 updateSum(node
->parent
,
194 node
->isLeftNode
, node
->sumLeft
,
197 stack_dist
= Infinity
;
200 stack_dist
= updateSum(node
->parent
,
202 level
, stack_dist
, true);
208 // This method is a recursive function which calculates
209 // the node sums till the root.
211 StackDistCalc::getSum(Node
* node
, bool from_left
, uint64_t sum_from_below
,
212 uint64_t stack_dist
, uint64_t level
) const
215 // Variable stack_dist is updated only
216 // when arriving from Left.
218 stack_dist
+= node
->sumRight
;
221 // Recursively call the getSum operation till the
222 // root node is reached
224 stack_dist
= getSum(node
->parent
, node
->isLeftNode
,
225 node
->sumLeft
+ node
->sumRight
,
232 // This function is called by the calcStackDistance function
234 StackDistCalc::getSumsLeavesToRoot(Node
* node
) const
236 return getSum(node
->parent
, node
->isLeftNode
, 0, 0, 0);
239 // Update tree is a tree balancing operation which maintains
240 // the binary tree structure. This method is called whenever
241 // index%2 == 0 (i.e. every alternate cycle)
242 // The two main operation are :
243 // OP1. moving the root node one layer up if index counter
244 // crosses power of 2
245 // OP2. Addition of intermediate nodes as and when required
246 // and linking them to their parents in the layer above.
248 StackDistCalc::updateTree()
252 if (isPowerOf2(index
)) {
253 // OP1. moving the root node one layer up if index counter
254 // crosses power of 2
255 // If index counter crosses a power of 2, then add a
256 // new tree layer above and create a new Root node in it.
257 // After the root is created the old node
258 // in the layer below is updated to point to this
259 // newly created root node. The sum_l of this new root node
260 // becomes the sum_l + sum_r of the old node.
262 // After this root update operation a chain of intermediate
263 // nodes is created from root layer to tree[1](one layer
264 // above the leaf layer)
266 // Create a new root node
267 Node
* newRootNode
= new Node();
269 // Update its sum_l as the sum_l+sum_r from below
270 newRootNode
->sumLeft
= tree
[getTreeDepth()][0]->sumRight
+
271 tree
[getTreeDepth()][0]->sumLeft
;
272 // Update its discard left flag if the node below has
273 // has both discardLeft and discardRight set.
274 newRootNode
->discardLeft
= tree
[getTreeDepth()][0]->discardLeft
&&
275 tree
[getTreeDepth()][0]->discardRight
;
277 // Map type variable, representing a layer in the tree
278 IndexNodeMap treeLevel
;
279 // Add a new layer to the tree
280 tree
.push_back(treeLevel
);
281 nextIndex
.push_back(1);
282 tree
[getTreeDepth()][newRootNode
->nodeIndex
] = newRootNode
;
284 // Update the parent pointer at lower layer to
285 // point to newly created root node
286 tree
[getTreeDepth() - 1][0]->parent
= tree
[getTreeDepth()][0];
288 // Add intermediate nodes from root till bottom (one layer above the
290 for (i
= getTreeDepth() - 1; i
>= 1; --i
) {
291 Node
* newINode
= new Node();
292 // newNode is left or right child depending on the number of nodes
294 if (nextIndex
[i
] % 2 == 0) {
295 newINode
->isLeftNode
= true;
297 newINode
->isLeftNode
= false;
300 newINode
->parent
= tree
[i
+ 1][nextIndex
[i
+ 1] - 1];
301 newINode
->nodeIndex
= ++nextIndex
[i
] - 1;
302 tree
[i
][newINode
->nodeIndex
] = newINode
;
305 // OP2. Addition of intermediate nodes as and when required
306 // and linking them to their parents in the layer above.
308 // At layer 1 a new INode is added whenever index%(2^1)==0
311 // At layer 2 a new INode is added whenever index%(2^2)==0
314 // At layer 3 a new INode is added whenever index%(2^3)==0
318 // At layer N a new INode is added whenever index%(2^N)==0
319 // (multiples of 2^N)
320 for (i
= getTreeDepth() - 1; i
>= 1; --i
) {
321 // Traverse each layer from root to leaves and add a new
322 // intermediate node if required. Link the parent_ptr of
323 // the new node to the parent in the above layer.
325 if ((index
% (1 << i
)) == 0) {
326 // Checks if current (index % 2^treeDepth) == 0 if true
327 // a new node at that layer is created
328 Node
* newINode
= new Node();
330 // newNode is left or right child depending on the
331 // number of nodes in that layer.
332 if (nextIndex
[i
] % 2 == 0) {
333 newINode
->isLeftNode
= true;
335 newINode
->isLeftNode
= false;
338 // Pointing to its parent in the upper layer
339 newINode
->parent
= tree
[i
+ 1][nextIndex
[i
+ 1] - 1];
340 newINode
->nodeIndex
= ++nextIndex
[i
] - 1;
341 tree
[i
][newINode
->nodeIndex
] = newINode
;
347 // This function is called everytime to get the stack distance and add
348 // a new node. A feature to mark an old node in the tree is
349 // added. This is useful if it is required to see the reuse
350 // pattern. For example, BackInvalidates from the lower level (Membus)
351 // to L2, can be marked (isMarked flag of Node set to True). And then
352 // later if this same address is accessed by L1, the value of the
353 // isMarked flag would be True. This would give some insight on how
354 // the BackInvalidates policy of the lower level affect the read/write
355 // accesses in an application.
356 std::pair
< uint64_t, bool>
357 StackDistCalc::calcStackDistAndUpdate(const Addr r_address
, bool addNewNode
)
361 auto ai
= aiMap
.lower_bound(r_address
);
363 // Default value of flag indicating as the left or right leaf
365 // Default value of isMarked flag for each node.
367 // By default stackDistacne is treated as infinity
370 // Lookup aiMap by giving address as the key:
371 // If found take address and Lookup in tree
372 // Update tree from leaves by making B(found index) = 0
373 // Add sums to right till root while Updating them
374 // Stack Distance of that address sums to right
375 if (ai
!= aiMap
.end() && !(aiMap
.key_comp()(r_address
, ai
->first
))) {
376 // key already exists
377 // save the index counter value when this address was
378 // encountered before and update it to the current index value
379 uint64_t r_index
= ai
->second
;
382 // Update aiMap aiMap(Address) = current index
385 aiMap
.erase(r_address
);
388 // Call update tree operation on the tree starting with
389 // the r_index value found above. This function would return
390 // the value of the stack distcance.
391 stack_dist
= updateSumsLeavesToRoot(tree
[0][r_index
], false);
392 newLeafNode
= tree
[0][r_index
];
393 // determine if this node was marked earlier
394 _mark
= newLeafNode
->isMarked
;
396 tree
[0].erase(r_index
);
399 // Update aiMap aiMap(Address) = current index
400 aiMap
[r_address
] = index
;
402 // Update infinity bin count
403 // By default stackDistacne is treated as infinity
404 stack_dist
= Infinity
;
408 // If index%2 == 0 then update tree
409 if (index
% 2 == 0) {
412 // At odd values of index counter, a new right-type node is
413 // added to the leaf layer, else a left-type node is added
417 // Add new leaf node in the leaf layer (tree[0])
418 // set n_index = current index
419 newLeafNode
= new Node();
421 newLeafNode
->nodeIndex
=index
;
422 newLeafNode
->isLeftNode
=isLeft
;
423 // Point the parent pointer to the intermediate node above
424 newLeafNode
->parent
= tree
[1][nextIndex
[1] - 1];
425 tree
[0][index
] = newLeafNode
;
426 // call an update operation which would update the tree after
427 // addition of this new leaf node.
428 updateSumsLeavesToRoot(tree
[0][index
], true);
432 // This function checks the sanity of the tree to make sure the
433 // last node in the link of parent pointers is the root node.
434 // It takes a leaf node as an argument and traveses upwards till
435 // the root layer to check if the last parent is null
436 sanityCheckTree(tree
[0][index
]);
438 // Push the same element in debug stack, and check
439 uint64_t verify_stack_dist
= verifyStackDist(r_address
, true);
440 panic_if(verify_stack_dist
!= stack_dist
,
441 "Expected stack-distance for address \
442 %#lx is %#lx but found %#lx",
443 r_address
, verify_stack_dist
, stack_dist
);
447 // The index counter is updated at the end of each transaction
448 // (unique or non-unique)
452 return (std::make_pair(stack_dist
, _mark
));
455 // This function is called everytime to get the stack distance
456 // no new node is added. It can be used to mark a previous access
457 // and inspect the value of the mark flag.
458 std::pair
< uint64_t, bool>
459 StackDistCalc::calcStackDist(const Addr r_address
, bool mark
)
461 // Default value of isMarked flag for each node.
464 auto ai
= aiMap
.lower_bound(r_address
);
466 // By default stackDistacne is treated as infinity
467 uint64_t stack_dist
= 0;
469 // Lookup aiMap by giving address as the key:
470 // If found take address and Lookup in tree
471 // Add sums to right till root
472 // Stack Distance of that address sums to right
473 if (ai
!= aiMap
.end() && !(aiMap
.key_comp()(r_address
, ai
->first
))) {
474 // key already exists
475 // save the index counter value when this address was
476 // encountered before
477 uint64_t r_index
= ai
->second
;
479 // Get the value of mark flag if previously marked
480 _mark
= tree
[0][r_index
]->isMarked
;
481 // Mark the leaf node if required
482 tree
[0][r_index
]->isMarked
= mark
;
484 // Call get sums operation on the tree starting with
485 // the r_index value found above. This function would return
486 // the value of the stack distcance.
487 stack_dist
= getSumsLeavesToRoot(tree
[0][r_index
]);
489 // Update infinity bin count
490 // By default stackDistacne is treated as infinity
491 stack_dist
= Infinity
;
496 // Calculate the SD of the same address in the debug stack
497 uint64_t verify_stack_dist
= verifyStackDist(r_address
);
498 panic_if(verify_stack_dist
!= stack_dist
,
499 "Expected stack-distance for address \
500 %#lx is %#lx but found %#lx",
501 r_address
, verify_stack_dist
, stack_dist
);
506 return std::make_pair(stack_dist
, _mark
);
510 // Simple sanity check for the tree
512 StackDistCalc::sanityCheckTree(const Node
* node
, uint64_t level
) const
514 const Node
* next_up
= node
->parent
;
516 for (uint64_t i
= level
+ 1; i
< getTreeDepth() - level
; ++i
) {
517 next_up
= next_up
->parent
;
518 panic_if(!next_up
, "Sanity check failed for node %ull \n",
522 // At the root layer the parent_ptr should be null
523 panic_if(next_up
->parent
, "Sanity check failed for node %ull \n",
527 // This method can be called to compute the stack distance in a naive
528 // way It can be used to verify the functionality of the stack
529 // distance calculator. It uses std::vector to compute the stack
530 // distance using a naive stack.
532 StackDistCalc::verifyStackDist(const Addr r_address
, bool update_stack
)
535 uint64_t stack_dist
= 0;
536 auto a
= stack
.rbegin();
538 for (; a
!= stack
.rend(); ++a
) {
539 if (*a
== r_address
) {
550 stack
.erase(a
.base());
552 stack_dist
= Infinity
;
556 stack
.push_back(r_address
);
561 // This method is useful to print top n entities in the stack.
563 StackDistCalc::printStack(int n
) const
568 DPRINTF(StackDist
, "Printing last %d entries in tree\n", n
);
570 // Walk through leaf layer to display the last n nodes
571 for (auto it
= tree
[0].rbegin(); (count
< n
) && (it
!= tree
[0].rend());
574 uint64_t r_index
= node
->nodeIndex
;
576 // Lookup aiMap using the index returned by the leaf iterator
577 for (auto ai
= aiMap
.rbegin(); ai
!= aiMap
.rend(); ++ai
) {
578 if (ai
->second
== r_index
) {
579 DPRINTF(StackDist
,"Tree leaves, Rightmost-[%d] = %#lx\n",
586 DPRINTF(StackDist
,"Tree depth = %#ld\n", getTreeDepth());
589 DPRINTF(StackDist
,"Printing Last %d entries in VerifStack \n", n
);
591 for (auto a
= stack
.rbegin(); (count
< n
) && (a
!= stack
.rend());
593 DPRINTF(StackDist
, "Verif Stack, Top-[%d] = %#lx\n", count
, *a
);