public Win32PageFileBackedMemoryMappedPager(string name, long?initialFileSize = null)
{
_name = name;
Win32NativeMethods.SYSTEM_INFO systemInfo;
Win32NativeMethods.GetSystemInfo(out systemInfo);
AllocationGranularity = systemInfo.allocationGranularity;
_totalAllocationSize = initialFileSize.HasValue ? NearestSizeToAllocationGranularity(initialFileSize.Value) : systemInfo.allocationGranularity;
_instanceId = Interlocked.Increment(ref _counter);
PagerState.Release();
Debug.Assert(AllocationGranularity % PageSize == 0);
NumberOfAllocatedPages = _totalAllocationSize / PageSize;
PagerState = CreateInitialPagerState(_totalAllocationSize);
}
private bool TryFindContinuousMemory(ulong size, out byte *foundAddressPtr)
{
foundAddressPtr = null;
try
{
foundAddressPtr = Win32NativeMethods.VirtualAlloc(null, new UIntPtr(size), Win32NativeMethods.AllocationType.RESERVE,
Win32NativeMethods.MemoryProtection.READWRITE);
return(foundAddressPtr != null && foundAddressPtr != (byte *)0);
}
finally
{
if (foundAddressPtr != null && foundAddressPtr != (byte *)0)
{
Win32NativeMethods.VirtualFree(foundAddressPtr, UIntPtr.Zero, Win32NativeMethods.FreeType.MEM_RELEASE);
}
}
}
public override void TryPrefetchingWholeFile()
{
if (CanPrefetch == false)
{
return; // not supported
}
var entries = stackalloc Win32MemoryMapNativeMethods.WIN32_MEMORY_RANGE_ENTRY[PagerState.AllocationInfos.Length];
for (int i = 0; i < PagerState.AllocationInfos.Length; i++)
{
entries[i].VirtualAddress = PagerState.AllocationInfos[i].BaseAddress;
entries[i].NumberOfBytes = (IntPtr)PagerState.AllocationInfos[i].Size;
}
if (Win32MemoryMapNativeMethods.PrefetchVirtualMemory(Win32NativeMethods.GetCurrentProcess(),
(UIntPtr)PagerState.AllocationInfos.Length, entries, 0) == false)
{
throw new Win32Exception();
}
}
public override void MaybePrefetchMemory(List <long> pagesToPrefetch)
{
if (CanPrefetch == false)
{
return; // not supported
}
if (pagesToPrefetch.Count == 0)
{
return;
}
var entries = new Win32MemoryMapNativeMethods.WIN32_MEMORY_RANGE_ENTRY[pagesToPrefetch.Count];
for (int i = 0; i < entries.Length; i++)
{
entries[i].NumberOfBytes = (IntPtr)(4 * PageSize);
entries[i].VirtualAddress = AcquirePagePointer(null, pagesToPrefetch[i]);
}
fixed(Win32MemoryMapNativeMethods.WIN32_MEMORY_RANGE_ENTRY *entriesPtr = entries)
{
Win32MemoryMapNativeMethods.PrefetchVirtualMemory(Win32NativeMethods.GetCurrentProcess(), (UIntPtr)PagerState.AllocationInfos.Length, entriesPtr, 0);
}
}
public override void MaybePrefetchMemory(List <Page> sortedPages)
{
if (sortedPages.Count == 0)
{
return;
}
if (IsWindows8OrNewer() == false)
{
return; // not supported
}
var list = new List <Win32MemoryMapNativeMethods.WIN32_MEMORY_RANGE_ENTRY>();
long lastPage = -1;
const int numberOfPagesInBatch = 8;
int sizeInPages = numberOfPagesInBatch; // OS uses 32K when you touch a page, let us reuse this
foreach (var page in sortedPages)
{
if (lastPage == -1)
{
lastPage = page.PageNumber;
}
var numberOfPagesInLastPage = page.IsOverflow == false
? 1
: GetNumberOfOverflowPages(page.OverflowSize);
var endPage = page.PageNumber + numberOfPagesInLastPage - 1;
if (endPage <= lastPage + sizeInPages)
{
continue; // already within the allocation granularity we have
}
if (page.PageNumber <= lastPage + sizeInPages + numberOfPagesInBatch)
{
while (endPage > lastPage + sizeInPages)
{
sizeInPages += numberOfPagesInBatch;
}
continue;
}
list.Add(new Win32MemoryMapNativeMethods.WIN32_MEMORY_RANGE_ENTRY
{
NumberOfBytes = (IntPtr)(sizeInPages * AbstractPager.PageSize),
VirtualAddress = AcquirePagePointer(lastPage)
});
lastPage = page.PageNumber;
sizeInPages = numberOfPagesInBatch;
while (endPage > lastPage + sizeInPages)
{
sizeInPages += numberOfPagesInBatch;
}
}
list.Add(new Win32MemoryMapNativeMethods.WIN32_MEMORY_RANGE_ENTRY
{
NumberOfBytes = (IntPtr)(sizeInPages * PageSize),
VirtualAddress = AcquirePagePointer(lastPage)
});
fixed(Win32MemoryMapNativeMethods.WIN32_MEMORY_RANGE_ENTRY *entries = list.ToArray())
{
Win32MemoryMapNativeMethods.PrefetchVirtualMemory(Win32NativeMethods.GetCurrentProcess(),
(UIntPtr)list.Count,
entries, 0);
}
}
