internal static unsafe void Verify(UnusedBlockHeader *header)
{
VTable.Assert(header->magic == (UIntPtr)magicNumber,
"Bad magic number in UnusedBlockHeader");
VTable.Assert(header->count > 0,
"Count <= 0 in UnusedBlockHeader");
VTable.Assert(header->prev->next == header,
"UnusedBlockHeader not linked properly (1)");
if (header->next != null)
{
VTable.Assert(header->next->prev == header,
"UnusedBlockHeader not linked properly (2)");
}
UIntPtr count = header->count;
UnusedBlockHeader *tailBlock = (UnusedBlockHeader *)
(((UIntPtr)header) + PageTable.RegionSize(count - 1));
VTable.Assert(tailBlock->curr == header,
"UnusedBlockHeader tail->curr is incorrect");
if (PageManager.SlowDebug)
{
UIntPtr page = PageTable.Page((UIntPtr)header);
for (UIntPtr i = UIntPtr.Zero; i < count; i++)
{
VTable.Assert(PageTable.IsUnusedPage(page + i) &&
PageTable.IsMyPage(page + i),
"Incorrect page in unused region");
}
}
}
internal static void VerifyUnusedRegion(UIntPtr startPage,
UIntPtr endPage)
{
// Verify that all of the pages are of the same Clean/Dirty type.
PageType startType = PageTable.Type(startPage);
for (UIntPtr page = startPage; page < endPage; ++page)
{
VTable.Assert(startType == PageTable.Type(page),
"Unused page types don't match in region");
}
if (startPage > UIntPtr.Zero &&
PageTable.IsUnusedPage(startPage - 1) &&
PageTable.IsMyPage(startPage - 1))
{
// We have already checked the region
return;
}
UIntPtr regionAddr = PageTable.PageAddr(startPage);
UnusedBlockHeader *regionHeader = (UnusedBlockHeader *)regionAddr;
UIntPtr pageCount = regionHeader->count;
VTable.Assert
(pageCount >= (endPage - startPage),
"Region-to-verify is larger than its header specifies");
endPage = startPage + pageCount;
for (UIntPtr page = startPage; page < endPage; ++page)
{
VTable.Assert(PageTable.IsUnusedPage(page) &&
PageTable.IsMyPage(page),
"Non my-unused page in unused region");
PageManager.VerifyUnusedPage
(page, (page == startPage) || (page == (endPage - 1)));
}
VTable.Assert(!(endPage < PageTable.pageTableCount &&
PageTable.IsUnusedPage(endPage) &&
PageTable.IsMyPage(endPage)),
"My-unused page immediately after unused region");
// Verify that the region is correctly linked into the
// list of unused memory blocks
int slot = SlotFromCount(pageCount);
UnusedBlockHeader *header = unusedMemoryBlocks[slot].next;
UnusedBlockHeader.Verify(header);
while (regionAddr != (UIntPtr)header)
{
header = header->next;
VTable.Assert(header != null,
"Unused region not list for its slot number");
UnusedBlockHeader.Verify(header);
}
}
internal static unsafe void Initialize(UnusedBlockHeader *header,
UIntPtr count)
{
header->magic = (UIntPtr)magicNumber;
header->next = null;
header->prev = null;
header->count = count;
UnusedBlockHeader *tailBlock = (UnusedBlockHeader *)
(((UIntPtr)header) + PageTable.RegionSize(count - 1));
tailBlock->curr = header;
}
private static void MarkUnusedPages(Thread currentThread,
UIntPtr startPage,
UIntPtr pageCount,
bool fCleanPages)
{
Trace.Log(Trace.Area.Page,
"MarkUnusedPages start={0:x} count={1:x}",
__arglist(startPage, pageCount));
UIntPtr endPage = startPage + pageCount;
if (avoidDirtyPages && !fCleanPages)
{
UIntPtr dirtyStartAddr = PageTable.PageAddr(startPage);
UIntPtr dirtySize = PageTable.RegionSize(pageCount);
Util.MemClear(dirtyStartAddr, dirtySize);
fCleanPages = true;
}
bool iflag = EnterMutex(currentThread);
try {
if (endPage < PageTable.pageTableCount)
{
if (PageTable.IsUnusedPage(endPage) &&
PageTable.IsMyPage(endPage))
{
UIntPtr regionSize = UnlinkUnusedPages(endPage);
endPage += regionSize;
}
}
UIntPtr queryStartPage = startPage - 1;
UIntPtr newStartPage = startPage;
if (PageTable.IsUnusedPage(queryStartPage) &&
PageTable.IsMyPage(queryStartPage))
{
UnusedBlockHeader *tailUnused = (UnusedBlockHeader *)
PageTable.PageAddr(queryStartPage);
UIntPtr newStartAddr = (UIntPtr)tailUnused->curr;
newStartPage = PageTable.Page(newStartAddr);
UIntPtr regionSize = UnlinkUnusedPages(newStartPage);
VTable.Assert(newStartPage + regionSize == startPage);
}
PageType pageType =
fCleanPages ? PageType.UnusedClean : PageType.UnusedDirty;
PageTable.SetType(startPage, pageCount, pageType);
LinkUnusedPages(newStartPage, endPage - newStartPage, false);
} finally {
LeaveMutex(currentThread, iflag);
}
}
private static void LinkUnusedPages(UIntPtr startPage,
UIntPtr pageCount,
bool asVictim)
{
if (PageManager.SlowDebug)
{
for (UIntPtr i = startPage; i < startPage + pageCount; i++)
{
VTable.Assert(PageTable.IsUnusedPage(i) &&
PageTable.IsMyPage(i),
"Incorrect page to link into unused region");
}
}
Trace.Log(Trace.Area.Page,
"LinkUnusedPages start={0:x} count={1:x}",
__arglist(startPage, pageCount));
VTable.Deny(startPage > UIntPtr.Zero &&
PageTable.IsUnusedPage(startPage - 1) &&
PageTable.IsMyPage(startPage - 1));
VTable.Deny(startPage + pageCount > PageTable.pageTableCount);
VTable.Deny(startPage + pageCount < PageTable.pageTableCount &&
PageTable.IsUnusedPage(startPage + pageCount) &&
PageTable.IsMyPage(startPage + pageCount));
UnusedBlockHeader *header = (UnusedBlockHeader *)
PageTable.PageAddr(startPage);
UnusedBlockHeader.Initialize(header, pageCount);
int slot = SlotFromCount(pageCount);
// Unused blocks are linked into the free list either as the result of a collection
// or as a result of carving a big block into a smaller allocation and a remainder.
// When such a remainder is linked back into the free list, it is identified as a
// victim. We favor subsequent allocations from these victims, in an attempt to
// reduce fragmentation. This is achieved by keeping victims at the head of the
// free list.
//
// TODO: the long term solution is to perform best fit on the free list.
if (asVictim || unusedMemoryBlocks[slot].next == null)
{
fixed(UnusedBlockHeader *listHeader = &unusedMemoryBlocks[slot])
{
UnusedBlockHeader.InsertNext(listHeader, header);
}
}
else
{
UnusedBlockHeader *listHeader = unusedMemoryBlocks[slot].next;
UnusedBlockHeader.InsertNext(listHeader, header);
}
}
private static UIntPtr UnlinkUnusedPages(UIntPtr startPage)
{
VTable.Assert(PageTable.IsUnusedPage(startPage) &&
PageTable.IsMyPage(startPage));
VTable.Deny(startPage > UIntPtr.Zero &&
PageTable.IsUnusedPage(startPage - 1) &&
PageTable.IsMyPage(startPage - 1));
UnusedBlockHeader *header = (UnusedBlockHeader *)
PageTable.PageAddr(startPage);
UIntPtr pageCount = UnusedBlockHeader.Remove(header);
Trace.Log(Trace.Area.Page,
"UnlinkUnusedPages start={0:x} count={1:x}",
__arglist(startPage, pageCount));
return(pageCount);
}
internal static unsafe void InsertNext(UnusedBlockHeader *header,
UnusedBlockHeader *newNext)
{
//Trace.Log(Trace.Area.Page,
// "UnusedBlockHeader.InsertNext {0} count={1}",
// __arglist(newNext, newNext->count));
UnusedBlockHeader *oldNext = header->next;
header->next = newNext;
newNext->next = oldNext;
newNext->prev = header;
if (oldNext != null)
{
oldNext->prev = newNext;
}
UnusedBlockHeader.Verify(newNext);
}
private static UIntPtr FindUnusedPages(Thread currentThread,
UIntPtr pageCount,
PageType newType)
{
VTable.Deny(PageTable.IsUnusedPageType(newType));
int slot = SlotFromCount(pageCount);
Trace.Log(Trace.Area.Page,
"FindUnusedPages count={0:x} slot={1}",
__arglist(pageCount, slot));
bool iflag = EnterMutex(currentThread);
try {
while (slot < 32)
{
UnusedBlockHeader *header = unusedMemoryBlocks[slot].next;
while (header != null)
{
if (header->count >= pageCount)
{
UIntPtr startPage =
PageTable.Page((UIntPtr)header);
UIntPtr regionSize = UnlinkUnusedPages(startPage);
SetPageTypeClean(startPage, pageCount, newType);
if (regionSize > pageCount)
{
UIntPtr restCount = regionSize - pageCount;
UIntPtr endPage = startPage + pageCount;
LinkUnusedPages(endPage, restCount, true);
}
Trace.Log(Trace.Area.Page,
"FindUnusedPages success {0:x}",
__arglist(startPage));
return(startPage);
}
header = header->next;
}
slot++;
}
return(UIntPtr.Zero);
} finally {
LeaveMutex(currentThread, iflag);
}
}
internal static UIntPtr TotalUnusedPages()
{
Thread currentThread = Thread.CurrentThread;
UIntPtr pageCount = (UIntPtr)0;
bool iflag = EnterMutex(currentThread);
try {
for (int slot = 0; slot < 32; slot++)
{
UnusedBlockHeader *header = unusedMemoryBlocks[slot].next;
while (header != null)
{
pageCount += header->count;
header = header->next;
}
}
return(pageCount);
} finally {
LeaveMutex(currentThread, iflag);
}
}
internal static unsafe UIntPtr Remove(UnusedBlockHeader *header)
{
//Trace.Log(Trace.Area.Page,
// "UnusedBlockHeader.Remove {0} count={1}",
// __arglist(this.prev->next, this.count));
UnusedBlockHeader.Verify(header);
header->prev->next = header->next;
if (header->next != null)
{
header->next->prev = header->prev;
}
UIntPtr result = header->count;
header->magic = UIntPtr.Zero;
header->prev = null;
header->next = null;
header->count = UIntPtr.Zero;
UnusedBlockHeader *tailBlock = (UnusedBlockHeader *)
(((UIntPtr)header) + PageTable.RegionSize(result - 1));
tailBlock->curr = null;
return(result);
}
internal static bool TryReserveUnusedPages(Thread currentThread,
UIntPtr startPage,
UIntPtr pageCount,
PageType newType,
ref bool fCleanPages)
{
Trace.Log(Trace.Area.Page,
"TryReserveUnusedPages start={0:x} count={1:x}",
__arglist(startPage, pageCount));
VTable.Deny(PageTable.IsUnusedPageType(newType));
VTable.Assert(pageCount > UIntPtr.Zero);
VTable.Deny(startPage != UIntPtr.Zero &&
PageTable.IsUnusedPage(startPage - 1) &&
PageTable.IsMyPage(startPage - 1));
UIntPtr endPage = startPage + pageCount;
if (endPage > PageTable.pageTableCount)
{
return(false);
}
if (currentThread != null)
{
GC.CheckForNeededGCWork(currentThread);
}
bool iflag = EnterMutex(currentThread);
try {
// GC can occur and page can be collected.
if (startPage != UIntPtr.Zero &&
PageTable.IsUnusedPage(startPage - 1))
{
return(false);
}
if (!PageTable.IsUnusedPage(startPage) ||
!PageTable.IsMyPage(startPage))
{
return(false);
}
UnusedBlockHeader *header = (UnusedBlockHeader *)
PageTable.PageAddr(startPage);
if (header->count < pageCount)
{
return(false);
}
UIntPtr regionPages = UnlinkUnusedPages(startPage);
Trace.Log(Trace.Area.Page,
"TryReserveUnusedPages found={0:x}",
__arglist(regionPages));
SetPageTypeClean(startPage, pageCount, newType);
if (regionPages > pageCount)
{
UIntPtr suffixPages = regionPages - pageCount;
LinkUnusedPages(endPage, suffixPages, true);
}
} finally {
LeaveMutex(currentThread, iflag);
}
// Now that we are outside the Mutex, we should perform the
// real cleaning of the gotten pages
if (fCleanPages)
{
CleanFoundPages(startPage);
}
else
{
fCleanPages = FoundOnlyCleanPages(startPage);
}
return(true);
}
