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CostManager: cache one interval and re-use it when possible

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In a lot of cases, only one interval is used. This can cause
a lot of malloc/free cycles for only 56 bytes. By caching this
single interval and re-using it, we remove this cycle in most
frequent cases.

Change-Id: Ia22d583f60ae438c216612062316b20ecb34f029
This commit is contained in:
Pascal Massimino 2016-06-08 13:30:01 +02:00
parent 41b7e6b56e
commit 0481d42ad8
1 changed files with 23 additions and 9 deletions
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32
src/enc/backward_references.c
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@ -619,6 +619,8 @@ typedef struct {
double cost_cache_[MAX_LENGTH]; // Contains the GetLengthCost(cost_model, k).
float* costs_;
uint16_t* dist_array_;
CostInterval spare_; // most of the time, we only will be using a single
int spare_used_; // interval. => We re-use this one first if possible.
} CostManager;
static int IsCostCacheIntervalWritable(int start, int end) {
@ -642,7 +644,11 @@ static void CostManagerClear(CostManager* const manager) {
CostInterval* interval = manager->head_;
while (interval != NULL) {
CostInterval* const next = interval->next_;
WebPSafeFree(interval);
if (manager->spare_used_ && interval == &manager->spare_) {
manager->spare_used_ = 0;
} else {
WebPSafeFree(interval);
}
interval = next;
}
}
@ -663,6 +669,7 @@ static int CostManagerInit(CostManager* const manager,
manager->head_ = NULL;
manager->count_ = 0;
manager->dist_array_ = dist_array;
manager->spare_used_ = 0;
// Fill in the cost_cache_.
manager->cache_intervals_size_ = 1;
@ -793,8 +800,11 @@ static WEBP_INLINE void PopInterval(CostManager* const manager,
if (interval == NULL) return;
ConnectIntervals(manager, interval->previous_, next);
WebPSafeFree(interval);
if (interval == &manager->spare_) {
manager->spare_used_ = 0;
} else {
WebPSafeFree(interval);
}
--manager->count_;
assert(manager->count_ >= 0);
}
@ -857,12 +867,16 @@ static WEBP_INLINE void InsertInterval(CostManager* const manager,
UpdateCostPerInterval(manager, start, end, index, distance_cost);
return;
}
interval_new = (CostInterval*)WebPSafeMalloc(1, sizeof(*interval_new));
if (interval_new == NULL) {
// Write down the interval if we cannot create it.
UpdateCostPerInterval(manager, start, end, index, distance_cost);
return;
if (!manager->spare_used_) {
interval_new = &manager->spare_;
manager->spare_used_ = 1;
} else {
interval_new = (CostInterval*)WebPSafeMalloc(1, sizeof(*interval_new));
if (interval_new == NULL) {
// Write down the interval if we cannot create it.
UpdateCostPerInterval(manager, start, end, index, distance_cost);
return;
}
}
interval_new->distance_cost_ = distance_cost;