From 9c690222486361b7b14a824ee88c18fa7df39e0a Mon Sep 17 00:00:00 2001
From: Sasan Golchin <ahmad.golchin@mail.polimi.it>
Date: Thu, 26 May 2016 17:29:13 +0200
Subject: [PATCH] Context Switch time optimization (reduced by 0.6 us)
---
miosix/kernel/intrusive.h | 198 +++++++++++++++++---------------------
miosix/kernel/kernel.cpp | 30 ++++--
2 files changed, 114 insertions(+), 114 deletions(-)
diff --git a/miosix/kernel/intrusive.h b/miosix/kernel/intrusive.h
index 18c26560..1031d57f 100644
--- a/miosix/kernel/intrusive.h
+++ b/miosix/kernel/intrusive.h
@@ -694,30 +694,114 @@ public:
emptyListItem.prev = &emptyListItem;
}
- void push_back(T *item);
+ void push_back(T *item)
+ {
+ item->next = &emptyListItem;
+ item->prev = tail;
+ tail = item;
+ emptyListItem.prev = item;
+ if(head==&emptyListItem)
+ {
+ head = tail;
+ emptyListItem.next = head;
+ } else item->prev->next = item;
+ }
/**
* Removes the last element in the list.
*/
- void pop_back();
+ void pop_back()
+ {
+ if(tail == head)
+ {
+ //Note: this is safe also in the case of pop_back of an empty list
+ //by mistake
+ removeLastItem();
+ } else {
+ tail->prev->next = &emptyListItem;
+ emptyListItem.prev = tail->prev;
+ tail->prev = nullptr;
+ tail->next = nullptr;
+ tail = static_cast<T*>(emptyListItem.prev);
+ }
+ }
- void push_front(T *item);
+ void push_front(T *item)
+ {
+ item->prev = &emptyListItem;
+ if(head != &emptyListItem)
+ {
+ item->next = head;
+ item->next->prev = item;
+ emptyListItem.next = item;
+ } else {
+ item->next = &emptyListItem;
+ tail = item;
+ emptyListItem.prev = item;
+ emptyListItem.next = item;
+ }
+ head = item;
+ }
/**
* Removes the first item (head) of the list.
*/
- void pop_front();
+ void pop_front()
+ {
+ if(tail == head)
+ {
+ //Note: this is safe also in the case of pop_back of an empty list
+ //by mistake
+ removeLastItem();
+ } else {
+ head->next->prev = &emptyListItem;
+ head->prev = nullptr;
+ emptyListItem.next = head->next;
+ head->next = nullptr;
+ head = static_cast<T*>(emptyListItem.next);
+ }
+ }
/**
* Inserts the given item before the position indicated by the iterator
*/
- void insert(iterator position, T *item);
+ void insert(iterator position, T *item)
+ {
+ if(head==&emptyListItem)
+ {
+ head = item;
+ tail = item;
+ item->next = &emptyListItem;
+ item->prev = &emptyListItem;
+ emptyListItem.next = item;
+ emptyListItem.prev = item;
+ return;
+ }
+ item->next = static_cast<IntrusiveListItem *>(*position); //FIXME: do we need this upcast?
+ item->prev = static_cast<IntrusiveListItem *>(*position)->prev;
+ item->prev->next = item;
+ (*position)->prev = item;
+ if(item->prev == &emptyListItem) head = item;
+ if(item->next == &emptyListItem) tail = item;
+ }
/**
* Removes the specified item from the list.
* @param an iterator to the next item
*/
- iterator erase(iterator it);
+ iterator erase(iterator it)
+ {
+ if((*it)==&emptyListItem) return it;
+ iterator result = it;
+ result++;
+ (*it)->next->prev = (*it)->prev;
+ (*it)->prev->next = (*it)->next;
+ (*it)->next = nullptr;
+ (*it)->prev = nullptr;
+ head = static_cast<T*>(emptyListItem.next);
+ tail = static_cast<T*>(emptyListItem.prev);
+ return result;
+ }
iterator begin()
{
@@ -760,108 +844,6 @@ private:
T emptyListItem;
};
-template<typename T>
-void IntrusiveList<T>::push_back(T *item)
-{
- item->next = &emptyListItem;
- item->prev = tail;
- tail = item;
- emptyListItem.prev = item;
- if(head==&emptyListItem)
- {
- head = tail;
- emptyListItem.next = head;
- } else item->prev->next = item;
-}
-
-template<typename T>
-void IntrusiveList<T>::pop_back()
-{
- if(tail == head)
- {
- //Note: this is safe also in the case of pop_back of an empty list
- //by mistake
- removeLastItem();
- } else {
- tail->prev->next = &emptyListItem;
- emptyListItem.prev = tail->prev;
- tail->prev = nullptr;
- tail->next = nullptr;
- tail = static_cast<T*>(emptyListItem.prev);
- }
-}
-
-template<typename T>
-void IntrusiveList<T>::push_front(T *item)
-{
- item->prev = &emptyListItem;
- if(head != &emptyListItem)
- {
- item->next = head;
- item->next->prev = item;
- emptyListItem.next = item;
- } else {
- item->next = &emptyListItem;
- tail = item;
- emptyListItem.prev = item;
- emptyListItem.next = item;
- }
- head = item;
-}
-
-template<typename T>
-void IntrusiveList<T>::pop_front()
-{
- if(tail == head)
- {
- //Note: this is safe also in the case of pop_back of an empty list
- //by mistake
- removeLastItem();
- } else {
- head->next->prev = &emptyListItem;
- head->prev = nullptr;
- emptyListItem.next = head->next;
- head->next = nullptr;
- head = static_cast<T*>(emptyListItem.next);
- }
-}
-
-template<typename T>
-void IntrusiveList<T>::insert(iterator position, T *item)
-{
- if(head==&emptyListItem)
- {
- head = item;
- tail = item;
- item->next = &emptyListItem;
- item->prev = &emptyListItem;
- emptyListItem.next = item;
- emptyListItem.prev = item;
- return;
- }
- item->next = static_cast<IntrusiveListItem *>(*position); //FIXME: do we need this upcast?
- item->prev = static_cast<IntrusiveListItem *>(*position)->prev;
- item->prev->next = item;
- (*position)->prev = item;
- if(item->prev == &emptyListItem) head = item;
- if(item->next == &emptyListItem) tail = item;
-}
-
-template<typename T>
-typename IntrusiveList<T>::iterator IntrusiveList<T>::erase(iterator it)
-{
- if((*it)==&emptyListItem) return it;
- iterator result = it;
- result++;
- (*it)->next->prev = (*it)->prev;
- (*it)->prev->next = (*it)->next;
- (*it)->next = nullptr;
- (*it)->prev = nullptr;
- head = static_cast<T*>(emptyListItem.next);
- tail = static_cast<T*>(emptyListItem.prev);
- return result;
-}
-
} //namespace miosix
#endif //INTRUSIVE_H
diff --git a/miosix/kernel/kernel.cpp b/miosix/kernel/kernel.cpp
index 81fae38d..6a940657 100644
--- a/miosix/kernel/kernel.cpp
+++ b/miosix/kernel/kernel.cpp
@@ -67,6 +67,8 @@ static volatile bool exist_deleted=false;
static IntrusiveList<SleepData> *sleepingList=nullptr;///list of sleeping threads
+static ContextSwitchTimer *timer = nullptr; // FIXME please
+
#ifndef USE_CSTIMER
static volatile long long tick=0;///<\internal Kernel tick
#endif //USE_CSTIMER
@@ -175,6 +177,7 @@ bool areInterruptsEnabled()
void startKernel()
{
+ timer = &ContextSwitchTimer::instance();
sleepingList = new(std::nothrow) IntrusiveList<SleepData>;
csRecord = new(std::nothrow) SleepData;
if(sleepingList==nullptr || csRecord==nullptr)
@@ -219,10 +222,10 @@ void startKernel()
// Dispatch the task to the architecture-specific function
#ifdef USE_CSTIMER
// Set the first checkpoint interrupt
- csRecord->p = 0;
+ csRecord->p = nullptr;
csRecord->wakeup_time = CSQUANTUM;
sleepingList->push_front(csRecord);
- miosix::ContextSwitchTimer::instance().IRQsetNextInterrupt(CSQUANTUM);
+ timer->IRQsetNextInterrupt(CSQUANTUM);
#endif //USE_CSTIMER
miosix_private::IRQportableStartKernel();
kernel_started=true;
@@ -251,7 +254,7 @@ long long getTick()
if(a==b) return a;
}
#else //USE_CSTIMER
- return ContextSwitchTimer::instance().getCurrentTick();
+ return timer->getCurrentTick();
#endif //USE_CSTIMER
}
@@ -279,7 +282,7 @@ void IRQaddToSleepingList(SleepData *x)
//Upon any change to the sleepingList the ContextSwitchTimer should have
//its interrupt set to the head of the list in order to keep it sync with
//the list
- ContextSwitchTimer::instance().IRQsetNextInterrupt(sleepingList->front()->wakeup_time);
+ timer->IRQsetNextInterrupt(sleepingList->front()->wakeup_time);
#endif
}
@@ -289,12 +292,27 @@ void IRQaddToSleepingList(SleepData *x)
*/
void IRQsetNextPreemption(long long preemptionTime)
{
+#ifdef USE_CSTIMER
// Remove all the preemption points from the list
IntrusiveList<SleepData>::iterator it(csRecord);
sleepingList->erase(it);
- //
+
+ //This piece of code is a duplication of IRQaddToSleepingList
+ //that is in-lined for performance issues
csRecord->wakeup_time = preemptionTime;
- IRQaddToSleepingList(csRecord); //It would also set the next timer interrupt
+ if(sleepingList->empty() || sleepingList->front()->wakeup_time >= preemptionTime)
+ {
+ sleepingList->push_front(csRecord);
+ } else {
+ auto it = sleepingList->begin();
+ while (it != sleepingList->end() && (*it)->wakeup_time < preemptionTime ) ++it;
+ sleepingList->insert(it,csRecord);
+ }
+ //Upon any change to the sleepingList the ContextSwitchTimer should have
+ //its interrupt set to the head of the list in order to keep it sync with
+ //the list
+ timer->IRQsetNextInterrupt(sleepingList->front()->wakeup_time);
+#endif
}
/**
* \internal
--
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