private LoadedPage MapPages(TransactionState state, long startPage, long size)
{
_globalMemory.EnterReadLock();
try
{
var addresses = _globalMapping.GetOrAdd(startPage,
_ => new ConcurrentSet <MappedAddresses>());
foreach (var addr in addresses)
{
if (addr.Size < size)
{
continue;
}
Interlocked.Increment(ref addr.Usages);
return(AddMappingToTransaction(state, startPage, size, addr));
}
var offset = startPage * Constants.Storage.PageSize;
if (offset + size > _totalAllocationSize)
{
ThrowInvalidMappingRequested(startPage, size);
}
var mmflags = _copyOnWriteMode ? MmapFlags.MAP_PRIVATE : MmapFlags.MAP_SHARED;
var startingBaseAddressPtr = Syscall.mmap64(IntPtr.Zero, (UIntPtr)size,
MmapProts.PROT_READ | MmapProts.PROT_WRITE,
mmflags, _fd, offset);
if (startingBaseAddressPtr.ToInt64() == -1)
//system didn't succeed in mapping the address where we wanted
{
var err = Marshal.GetLastWin32Error();
Syscall.ThrowLastError(err,
$"Unable to map {size / Constants.Size.Kilobyte:#,#0} kb starting at {startPage} on {FileName}");
}
NativeMemory.RegisterFileMapping(FileName.FullPath, startingBaseAddressPtr, size, GetAllocatedInBytes);
Interlocked.Add(ref _totalMapped, size);
var mappedAddresses = new MappedAddresses
{
Address = startingBaseAddressPtr,
File = FileName.FullPath,
Size = size,
StartPage = startPage,
Usages = 1
};
addresses.Add(mappedAddresses);
return(AddMappingToTransaction(state, startPage, size, mappedAddresses));
}
finally
{
_globalMemory.ExitReadLock();
}
}
private LoadedPage AddMappingToTransaction(TransactionState state, long startPage, long size, MappedAddresses mappedAddresses)
{
state.TotalLoadedSize += size;
state.AddressesToUnload.Add(mappedAddresses);
var loadedPage = new LoadedPage
{
Pointer = (byte *)mappedAddresses.Address,
NumberOfPages = (int)(size / Constants.Storage.PageSize),
StartPage = startPage
};
state.LoadedPages[startPage] = loadedPage;
return(loadedPage);
}