private void Decommit(ulong address, ulong size)
{
(ulong granularStart, ulong granularEnd) = GetAlignedRange(address, size);
ulong endAddress = address + size;
lock (_lock)
{
int mappingCount = _mappings.FindOverlapsNonOverlapping(granularStart, granularEnd - granularStart, ref _foundMappings);
int first = -1;
int last = -1;
for (int i = 0; i < mappingCount; i++)
{
SharedMemoryMapping mapping = _foundMappings[i];
if (mapping.OverlapsWith(address, size))
{
if (first == -1)
{
first = i;
}
last = i;
}
}
if (first == -1)
{
return; // Could not find any regions to decommit.
}
int lastReleasedBlock = -1;
bool releasedFirst = false;
bool releasedLast = false;
for (int i = last; i >= first; i--)
{
SharedMemoryMapping mapping = _foundMappings[i];
bool releaseEnd = true;
bool releaseStart = true;
if (i == last)
{
// If this is the last region, do not release the block if there is a page ahead of us, or the block continues after us. (it is keeping the block alive)
releaseEnd = last == mappingCount - 1;
// If the end region starts after the decommit end address, split and readd it after modifying its base address.
if (mapping.EndAddress > endAddress)
{
var newMapping = (SharedMemoryMapping)mapping.Split(endAddress);
_mappings.UpdateEndAddress(mapping);
_mappings.Add(newMapping);
if ((endAddress & MappingMask) != 0)
{
releaseEnd = false;
}
}
releasedLast = releaseEnd;
}
if (i == first)
{
// If this is the first region, do not release the block if there is a region behind us. (it is keeping the block alive)
releaseStart = first == 0;
// If the first region starts before the decommit address, split it by modifying its end address.
if (mapping.Address < address)
{
var oldMapping = mapping;
mapping = (SharedMemoryMapping)mapping.Split(address);
_mappings.UpdateEndAddress(oldMapping);
if ((address & MappingMask) != 0)
{
releaseStart = false;
}
}
releasedFirst = releaseStart;
}
_mappings.Remove(mapping);
ulong releasePointer = (mapping.EndAddress + MappingMask) & (~MappingMask);
for (int j = mapping.Blocks.Count - 1; j >= 0; j--)
{
int blockId = mapping.Blocks[j];
releasePointer -= MappingGranularity;
if (lastReleasedBlock == blockId)
{
// When committed regions are fragmented, multiple will have the same block id for their start/end granular block.
// Avoid releasing these blocks twice.
continue;
}
if ((j != 0 || releaseStart) && (j != mapping.Blocks.Count - 1 || releaseEnd))
{
ReleaseBackingBlock(releasePointer, blockId);
}
lastReleasedBlock = blockId;
}
}
ulong placeholderStart = (granularStart >> MappingBits) + (releasedFirst ? 0UL : 1UL);
ulong placeholderEnd = (granularEnd >> MappingBits) - (releasedLast ? 0UL : 1UL);
if (placeholderEnd > placeholderStart)
{
_placeholders.RemovePlaceholders(placeholderStart, placeholderEnd - placeholderStart, CoalescePlaceholder);
}
}
}
private void Commit(ulong address, ulong size)
{
(ulong granularStart, ulong granularEnd) = GetAlignedRange(address, size);
ulong endAddress = address + size;
lock (_lock)
{
// Search a bit before and after the new mapping.
// When adding our new mapping, we may need to join an existing mapping into our new mapping (or in some cases, to the other side!)
ulong searchStart = granularStart == 0 ? 0 : (granularStart - 1);
int mappingCount = _mappings.FindOverlapsNonOverlapping(searchStart, (granularEnd - searchStart) + 1, ref _foundMappings);
int first = -1;
int last = -1;
SharedMemoryMapping startOverlap = null;
SharedMemoryMapping endOverlap = null;
int lastIndex = (int)(address >> MappingBits);
int endIndex = (int)((endAddress + MappingMask) >> MappingBits);
int firstBlock = -1;
int endBlock = -1;
for (int i = 0; i < mappingCount; i++)
{
SharedMemoryMapping mapping = _foundMappings[i];
if (mapping.Address < address)
{
if (mapping.EndAddress >= address)
{
startOverlap = mapping;
}
if ((int)((mapping.EndAddress - 1) >> MappingBits) == lastIndex)
{
lastIndex = (int)((mapping.EndAddress + MappingMask) >> MappingBits);
firstBlock = mapping.Blocks.Last();
}
}
if (mapping.EndAddress > endAddress)
{
if (mapping.Address <= endAddress)
{
endOverlap = mapping;
}
if ((int)((mapping.Address) >> MappingBits) + 1 == endIndex)
{
endIndex = (int)((mapping.Address) >> MappingBits);
endBlock = mapping.Blocks.First();
}
}
if (mapping.OverlapsWith(address, size))
{
if (first == -1)
{
first = i;
}
last = i;
}
}
if (startOverlap == endOverlap && startOverlap != null)
{
// Already fully committed.
return;
}
var blocks = new List <int>();
int lastBlock = -1;
if (firstBlock != -1)
{
blocks.Add(firstBlock);
lastBlock = firstBlock;
}
bool hasMapped = false;
Action map = () =>
{
if (!hasMapped)
{
_placeholders.EnsurePlaceholders(address >> MappingBits, (granularEnd - granularStart) >> MappingBits, SplitPlaceholder);
hasMapped = true;
}
// There's a gap between this index and the last. Allocate blocks to fill it.
blocks.Add(MapBackingBlock(MappingGranularity * (ulong)lastIndex++));
};
if (first != -1)
{
for (int i = first; i <= last; i++)
{
SharedMemoryMapping mapping = _foundMappings[i];
int mapIndex = (int)(mapping.Address >> MappingBits);
while (lastIndex < mapIndex)
{
map();
}
if (lastBlock == mapping.Blocks[0])
{
blocks.AddRange(mapping.Blocks.Skip(1));
}
else
{
blocks.AddRange(mapping.Blocks);
}
lastIndex = (int)((mapping.EndAddress - 1) >> MappingBits) + 1;
}
}
while (lastIndex < endIndex)
{
map();
}
if (endBlock != -1 && endBlock != lastBlock)
{
blocks.Add(endBlock);
}
if (startOverlap != null && endOverlap != null)
{
// Both sides should be coalesced. Extend the start overlap to contain the end overlap, and add together their blocks.
_mappings.Remove(endOverlap);
startOverlap.ExtendTo(endOverlap.EndAddress, _mappings);
startOverlap.AddBlocks(blocks);
startOverlap.AddBlocks(endOverlap.Blocks);
}
else if (startOverlap != null)
{
startOverlap.ExtendTo(endAddress, _mappings);
startOverlap.AddBlocks(blocks);
}
else
{
var mapping = new SharedMemoryMapping(address, size, blocks);
if (endOverlap != null)
{
mapping.ExtendTo(endOverlap.EndAddress, _mappings);
mapping.AddBlocks(endOverlap.Blocks);
_mappings.Remove(endOverlap);
}
_mappings.Add(mapping);
}
}
}