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);
}
}
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);
}
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);
}
