acquire: Use priority queues and a 3 stage pipeline design

[apt.git] / apt-pkg / acquire.cc

diff --git a/apt-pkg/acquire.cc b/apt-pkg/acquire.cc
index b4d1b595931cf9a32bf4f01d8be19ad49d8de617..2ad6bc47f91c3a846ce658faeaab84acd37eda6c 100644 (file)
--- a/apt-pkg/acquire.cc
+++ b/apt-pkg/acquire.cc
@@ -894,9 +894,10 @@ pkgAcquire::Queue::~Queue()
 /* */
 bool pkgAcquire::Queue::Enqueue(ItemDesc &Item)
 {
+   QItem **OptimalI = &Items;
    QItem **I = &Items;
    // move to the end of the queue and check for duplicates here
-   for (; *I != 0; I = &(*I)->Next)
+   for (; *I != 0; ) {
       if (Item.URI == (*I)->URI)
       {
         if (_config->FindB("Debug::pkgAcquire::Worker",false) == true)
@@ -905,12 +906,22 @@ bool pkgAcquire::Queue::Enqueue(ItemDesc &Item)
         Item.Owner->Status = (*I)->Owner->Status;
         return false;
       }
+      // Determine the optimal position to insert: before anything with a
+      // higher priority.
+      int priority = (*I)->GetPriority();
+
+      I = &(*I)->Next;
+      if (priority >= Item.Owner->Priority()) {
+        OptimalI = I;
+      }
+   }
+
 
    // Create a new item
    QItem *Itm = new QItem;
    *Itm = Item;
-   Itm->Next = 0;
-   *I = Itm;
+   Itm->Next = *OptimalI;
+   *OptimalI = Itm;
    
    Item.Owner->QueueCounter++;   
    if (Items->Next == 0)
@@ -1060,16 +1071,24 @@ bool pkgAcquire::Queue::Cycle()
 
    // Look for a queable item
    QItem *I = Items;
+   int ActivePriority = 0;
    while (PipeDepth < (signed)MaxPipeDepth)
    {
-      for (; I != 0; I = I->Next)
+      for (; I != 0; I = I->Next) {
+        if (I->Owner->Status == pkgAcquire::Item::StatFetching)
+           ActivePriority = std::max(ActivePriority, I->GetPriority());
         if (I->Owner->Status == pkgAcquire::Item::StatIdle)
            break;
+      }
 
       // Nothing to do, queue is idle.
       if (I == 0)
         return true;
 
+      // This item has a lower priority than stuff in the pipeline, pretend
+      // the queue is idle
+      if (I->GetPriority() < ActivePriority)
+        return true;
       I->Worker = Workers;
       for (auto const &O: I->Owners)
         O->Status = pkgAcquire::Item::StatFetching;
@@ -1135,6 +1154,15 @@ APT_PURE unsigned long long pkgAcquire::Queue::QItem::GetMaximumSize() const     /*{
    return Maximum;
 }
                                                                        /*}}}*/
+APT_PURE int pkgAcquire::Queue::QItem::GetPriority() const     /*{{{*/
+{
+   int Priority = 0;
+   for (auto const &O: Owners)
+      Priority = std::max(Priority, O->Priority());
+
+   return Priority;
+}
+                                                                       /*}}}*/
 void pkgAcquire::Queue::QItem::SyncDestinationFiles() const            /*{{{*/
 {
    /* ensure that the first owner has the best partial file of all and