mirror of
https://github.com/reactos/reactos.git
synced 2024-07-06 04:35:07 +00:00
- Implement the algorithms for pool allocation and de-allocation:
- Only tested/works with nonpaged pool for now. - No support for session pool or special pool. - No support for pool tagging. - No support for accounting (free/available pages, etc). - No optimizations other than your average combine-with-previous-free and combine-with-next-free mechanisms to avoid fragmentation. - No support for debugging. - No consistency/validation checks. - Heavily commented for the inquiring mind. - Thread/MP safe. - Not used yet. svn path=/trunk/; revision=42245
This commit is contained in:
ReactOS Portable Systems Group
parent
e917c6e96d
commit
a6757c9637
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@ -82,4 +82,465 @@ InitializePool(IN POOL_TYPE PoolType,
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NULL);
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}
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PVOID
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NTAPI
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ExAllocateArmPoolWithTag(IN POOL_TYPE PoolType,
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IN SIZE_T NumberOfBytes,
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IN ULONG Tag)
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{
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POOL_TYPE PoolType;
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PPOOL_DESCRIPTOR PoolDesc;
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PLIST_ENTRY ListHead;
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PPOOL_HEADER Entry, NextEntry, FragmentEntry;
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KIRQL OldIrql;
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ULONG BlockSize, i;
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//
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// Some sanity checks
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//
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ASSERT(Tag != 0);
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ASSERT(Tag != ' GIB');
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ASSERT(NumberOfBytes != 0);
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//
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// Get the pool type and its corresponding vector for this request
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//
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PoolType = PoolType & BASE_POOL_TYPE_MASK;
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PoolDesc = PoolVector[PoolType];
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ASSERT(PoolDesc != NULL);
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//
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// Check if this is a big page allocation
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//
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if (NumberOfBytes > POOL_MAX_ALLOC)
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{
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//
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// Then just return the number of pages requested
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//
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return MiAllocatePoolPages(PoolType, NumberOfBytes);
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}
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//
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// Should never request 0 bytes from the pool, but since so many drivers do
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// it, we'll just assume they want 1 byte, based on NT's similar behavior
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//
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if (!NumberOfBytes) NumberOfBytes = 1;
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//
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// A pool allocation is defined by its data, a linked list to connect it to
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// the free list (if necessary), and a pool header to store accounting info.
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// Calculate this size, then convert it into a block size (units of pool
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// headers)
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//
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// Note that i cannot overflow (past POOL_LISTS_PER_PAGE) because any such
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// request would've been treated as a POOL_MAX_ALLOC earlier and resulted in
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// the direct allocation of pages.
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//
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i = (NumberOfBytes + sizeof(POOL_HEADER) + sizeof(LIST_ENTRY) - 1) /
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sizeof(POOL_HEADER);
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//
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// Loop in the free lists looking for a block if this size. Start with the
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// list optimized for this kind of size lookup
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//
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ListHead = &PoolDesc->ListHeads[i];
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do
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{
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//
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// Are there any free entries available on this list?
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//
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if (!IsListEmpty(ListHead))
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{
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//
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// Acquire the nonpaged pool lock now
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//
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OldIrql = KeAcquireQueuedSpinLock(LockQueueNonPagedPoolLock);
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//
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// And make sure the list still has entries
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//
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if (IsListEmpty(ListHead))
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{
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//
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// Someone raced us (and won) before we had a chance to acquire
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// the lock.
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//
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// Try again!
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//
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KeReleaseQueuedSpinLock(LockQueueNonPagedPoolLock, OldIrql);
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ListHead++;
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continue;
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}
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//
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// Remove a free entry from the list
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// Note that due to the way we insert free blocks into multiple lists
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// there is a guarantee that any block on this list will either be
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// of the correct size, or perhaps larger.
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//
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Entry = (PPOOL_HEADER)RemoveHeadList(ListHead) - 1;
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ASSERT(Entry->BlockSize >= i);
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ASSERT(Entry->PoolType == 0);
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//
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// Check if this block is larger that what we need. The block could
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// not possibly be smaller, due to the reason explained above (and
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// we would've asserted on a checked build if this was the case).
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//
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if (Entry->BlockSize != i)
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{
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//
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// Is there an entry before this one?
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//
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if (Entry->PreviousSize == 0)
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{
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//
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// There isn't anyone before us, so take the next block and
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// turn it into a fragment that contains the leftover data
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// that we don't need to satisfy the caller's request
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//
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FragmentEntry = Entry + i;
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FragmentEntry->BlockSize = Entry->BlockSize - i;
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//
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// And make it point back to us
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//
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FragmentEntry->PreviousSize = i;
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//
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// Now get the block that follows the new fragment and check
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// if it's still on the same page as us (and not at the end)
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//
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NextEntry = FragmentEntry + FragmentEntry->BlockSize;
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if (PAGE_ALIGN(NextEntry) != NextEntry)
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{
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//
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// Adjust this next block to point to our newly created
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// fragment block
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//
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NextEntry->PreviousSize = FragmentEntry->BlockSize;
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}
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}
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else
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{
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//
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// There is a free entry before us, which we know is smaller
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// so we'll make this entry the fragment instead
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//
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FragmentEntry = Entry;
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//
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// And then we'll remove from it the actual size required.
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// Now the entry is a leftover free fragment
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//
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Entry->BlockSize -= i;
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//
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// Now let's go to the next entry after the fragment (which
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// used to point to our original free entry) and make it
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// reference the new fragment entry instead.
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//
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// This is the entry that will actually end up holding the
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// allocation!
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//
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Entry += Entry->BlockSize;
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Entry->PreviousSize = FragmentEntry->BlockSize;
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//
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// And now let's go to the entry after that one and check if
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// it's still on the same page, and not at the end
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//
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NextEntry = Entry + i;
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if (PAGE_ALIGN(NextEntry) != NextEntry)
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{
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//
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// Make it reference the allocation entry
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//
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NextEntry->PreviousSize = i;
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}
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}
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//
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// Now our (allocation) entry is the right size
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//
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Entry->BlockSize = i;
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//
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// And the next entry is now the free fragment which contains
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// the remaining difference between how big the original entry
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// was, and the actual size the caller needs/requested.
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//
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FragmentEntry->PoolType = 0;
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BlockSize = FragmentEntry->BlockSize;
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//
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// Now check if enough free bytes remained for us to have a
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// "full" entry, which contains enough bytes for a linked list
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// and thus can be used for allocations (up to 8 bytes...)
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//
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if (BlockSize != 1)
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{
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//
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// Insert the free entry into the free list for this size
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//
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InsertTailList(&PoolDesc->ListHeads[BlockSize - 1],
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(PLIST_ENTRY)FragmentEntry + 1);
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}
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}
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//
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// We have found an entry for this allocation, so set the pool type
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// and release the lock since we're done
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//
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Entry->PoolType = PoolType + 1;
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KeReleaseQueuedSpinLock(LockQueueNonPagedPoolLock, OldIrql);
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//
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// Return the pool allocation
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//
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Entry->PoolTag = Tag;
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return ++Entry;
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}
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} while (++ListHead != &PoolDesc->ListHeads[POOL_LISTS_PER_PAGE]);
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//
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// There were no free entries left, so we have to allocate a new fresh page
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//
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Entry = MiAllocatePoolPages(PoolType, PAGE_SIZE);
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Entry->Ulong1 = 0;
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Entry->BlockSize = i;
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Entry->PoolType = PoolType + 1;
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//
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// This page will have two entries -- one for the allocation (which we just
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// created above), and one for the remaining free bytes, which we're about
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// to create now. The free bytes are the whole page minus what was allocated
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// and then converted into units of block headers.
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//
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BlockSize = (PAGE_SIZE / sizeof(POOL_HEADER)) - i;
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FragmentEntry = Entry + i;
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FragmentEntry->Ulong1 = 0;
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FragmentEntry->BlockSize = BlockSize;
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FragmentEntry->PreviousSize = i;
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//
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// Now check if enough free bytes remained for us to have a "full" entry,
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// which contains enough bytes for a linked list and thus can be used for
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// allocations (up to 8 bytes...)
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//
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if (FragmentEntry->BlockSize != 1)
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{
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//
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// Excellent -- acquire the nonpaged pool lock
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//
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OldIrql = KeAcquireQueuedSpinLock(LockQueueNonPagedPoolLock);
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//
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// And insert the free entry into the free list for this block size
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//
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InsertTailList(&PoolDesc->ListHeads[BlockSize - 1],
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(PLIST_ENTRY)FragmentEntry + 1);
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//
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// Release the nonpaged pool lock
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//
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KeReleaseQueuedSpinLock(LockQueueNonPagedPoolLock, OldIrql);
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}
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//
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// And return the pool allocation
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//
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Entry->PoolTag = Tag;
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return ++Entry;
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}
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PVOID
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NTAPI
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ExAllocateArmPool(POOL_TYPE PoolType,
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SIZE_T NumberOfBytes)
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{
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//
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// Use a default tag of "None"
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//
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return ExAllocatePoolWithTag(PoolType, NumberOfBytes, 'enoN');
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}
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VOID
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NTAPI
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ExFreeArmPoolWithTag(IN PVOID P,
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IN ULONG TagToFree)
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{
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PPOOL_HEADER Entry, NextEntry;
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ULONG BlockSize;
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KIRQL OldIrql;
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POOL_TYPE PoolType;
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PPOOL_DESCRIPTOR PoolDesc;
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BOOLEAN Combined = FALSE;
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//
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// Quickly deal with big page allocations
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//
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if (PAGE_ALIGN(P) == P) return (VOID)MiFreePoolPages(P);
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//
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// Get the entry for this pool allocation
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// The pointer math here may look wrong or confusing, but it is quite right
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//
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Entry = P;
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Entry--;
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//
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// Get the size of the entry, and it's pool type, then load the descriptor
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// for this pool type
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//
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BlockSize = Entry->BlockSize;
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PoolType = (Entry->PoolType & BASE_POOL_TYPE_MASK) - 1;
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PoolDesc = PoolVector[PoolType];
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//
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// Get the pointer to the next entry
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//
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NextEntry = Entry + BlockSize;
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//
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// Acquire the nonpaged pool lock
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//
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OldIrql = KeAcquireQueuedSpinLock(LockQueueNonPagedPoolLock);
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//
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// Check if the next allocation is at the end of the page
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//
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if (PAGE_ALIGN(NextEntry) != NextEntry)
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{
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//
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// We may be able to combine the block if it's free
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//
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if (NextEntry->PoolType == 0)
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{
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//
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// The next block is free, so we'll do a combine
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//
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Combined = TRUE;
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//
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// Make sure there's actual data in the block -- anything smaller
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// than this means we only have the header, so there's no linked list
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// for us to remove
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//
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if ((NextEntry->BlockSize != 1))
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{
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//
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// The block is at least big enough to have a linked list, so go
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// ahead and remove it
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//
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RemoveEntryList((PLIST_ENTRY)NextEntry + 1);
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}
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//
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// Our entry is now combined with the next entry
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//
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Entry->BlockSize = Entry->BlockSize + NextEntry->BlockSize;
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}
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}
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//
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// Now check if there was a previous entry on the same page as us
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//
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if (Entry->PreviousSize)
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{
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//
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// Great, grab that entry and check if it's free
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//
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NextEntry = Entry - Entry->PreviousSize;
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if (NextEntry->PoolType == 0)
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{
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//
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// It is, so we can do a combine
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//
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Combined = TRUE;
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//
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// Make sure there's actual data in the block -- anything smaller
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// than this means we only have the header so there's no linked list
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// for us to remove
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//
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if ((NextEntry->BlockSize != 1))
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{
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//
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// The block is at least big enough to have a linked list, so go
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// ahead and remove it
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//
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RemoveEntryList((PLIST_ENTRY)NextEntry + 1);
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}
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//
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// Combine our original block (which might've already been combined
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// with the next block), into the previous block
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//
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NextEntry->BlockSize = NextEntry->BlockSize + Entry->BlockSize;
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//
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// And now we'll work with the previous block instead
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//
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Entry = NextEntry;
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}
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}
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//
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// By now, it may have been possible for our combined blocks to actually
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// have made up a full page (if there were only 2-3 allocations on the
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// page, they could've all been combined).
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//
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if ((PAGE_ALIGN(Entry) == Entry) &&
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(PAGE_ALIGN(Entry + Entry->BlockSize) == Entry + Entry->BlockSize))
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{
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//
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// In this case, release the nonpaged pool lock, and free the page
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//
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KeReleaseQueuedSpinLock(LockQueueNonPagedPoolLock, OldIrql);
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return (VOID)MiFreePoolPages(Entry);
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}
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//
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// Otherwise, we now have a free block (or a combination of 2 or 3)
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//
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Entry->PoolType = 0;
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BlockSize = Entry->BlockSize;
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ASSERT(BlockSize != 1);
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//
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// Check if we actually did combine it with anyone
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//
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if (Combined)
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{
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//
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// Get the first combined block (either our original to begin with, or
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// the one after the original, depending if we combined with the previous)
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//
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NextEntry = Entry + BlockSize;
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//
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// As long as the next block isn't on a page boundary, have it point
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// back to us
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//
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if (PAGE_ALIGN(NextEntry) != NextEntry) NextEntry->PreviousSize = BlockSize;
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}
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//
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// Insert this new free block, and release the nonpaged pool lock
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//
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InsertHeadList(&PoolDesc->ListHeads[BlockSize - 1], (PLIST_ENTRY)Entry + 1);
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KeReleaseQueuedSpinLock(LockQueueNonPagedPoolLock, OldIrql);
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}
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VOID
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NTAPI
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ExFreeArmPool(PVOID P)
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{
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//
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// Just free without checking for the tag
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//
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ExFreeArmPoolWithTag(P, 0);
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}
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/* EOF */
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