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work on LaxMalloc

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lax1dude 2024-10-31 22:47:36 -07:00
parent 2b73f658d0
commit 5830392f60
1 changed files with 234 additions and 114 deletions
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316
core/src/main/java/org/teavm/runtime/LaxMalloc.java
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@ -84,64 +84,21 @@ public final class LaxMalloc {
if(bucket == 63) {
// special bucket for the huge allocations
// uses a different function
// uses a different slower function
return laxHugeAlloc(sizeBytes, cleared);
}
// load bitmask of buckets with free chunks
long bucketMask = Address.fromInt(ADDR_HEAP_BUCKETS_FREE_MASK).getLong();
// test the bucket mask if the bucket has any free chunks
if((bucketMask & (1L << bucket)) == 0l) {
// no more free chunks, let us first check if there are any
// chunks in the larger buckets we can split
long largerBucketsMask = (bucketMask & (0xFFFFFFFFFFFFFFFFL << (bucket + 1)));
if(largerBucketsMask != 0l) {
// at least one larger chunk exists
// we can quickly find it using the bitmask
int largerBucket = numberOfTrailingZerosL(largerBucketsMask);
// mask away the buckets that we know are too small for this allocation
bucketMask = (bucketMask & (0xFFFFFFFFFFFFFFFFL << bucket));
Address bucketStartAddr = Address.fromInt(ADDR_HEAP_BUCKETS_START).add(largerBucket << SIZEOF_PTR_SH);
Address chunkPtr = bucketStartAddr.getAddress();
int chunkSize = readChunkSize(chunkPtr);
int chunkNewSize = chunkSize - sizeBytes - 8; // -size - 2 ints - 2 more ints
// if the other half of the new chunk is too small, check an even larger bucket
// we should only need to look at an even larger bucket one more time before giving up
if(chunkNewSize - 8 < MIN_ALLOC_SIZE) {
//TODO
}
// remove the large chunk from its bucket
unlinkChunkFromFreeList(chunkPtr, chunkSize);
// provision the part of the large chunk we want
// there are no more buckets with free chunks
// need to sbrk
if(bucketMask == 0l) {
int sizePlusInts = sizeBytes + 8; // size + 2 ints
chunkPtr.putInt(sizePlusInts | 0x80000000); // size + in use flag
chunkPtr.add(sizeBytes + 4).putInt(sizePlusInts); // size integer at the end
// provision the other part of the chunk that we want to return to the free list
Address otherChunkPtr = chunkPtr.add(sizePlusInts);
otherChunkPtr.putInt(chunkNewSize); // size
otherChunkPtr.add(chunkNewSize - 4).putInt(chunkNewSize); // size (end)
// return the other part of the chunk to the free chunks list
linkChunkInFreeList(otherChunkPtr, chunkNewSize);
// +4 bytes to skip size
Address ret = chunkPtr.add(4);
// clear if requested
if(cleared) {
Allocator.fillZero(ret, sizeBytes);
}
return ret;
}else {
// No larger chunks already exist that we can split,
// time to sbrk
int sizePlusInts = sizeBytes + 8; // size + 2 ints
Address newChunk = growHeap(sizePlusInts);
Address newChunk = growHeap(sizePlusInts); // sbrk
// Out of memory
if(newChunk.toInt() == 0) {
@ -156,31 +113,87 @@ public final class LaxMalloc {
// we don't need to clear it because its new memory
return newChunk.add(4);
}
}else {
// At least one free chunk is available, get it from the bucket
Address bucketStartAddr = Address.fromInt(ADDR_HEAP_BUCKETS_START).add(bucket << SIZEOF_PTR_SH);
// at least one bucket exists containing a free chunk,
// quickly determine which bucket it is with bit hacks
int availableBucket = numberOfTrailingZerosL(bucketMask);
Address bucketStartAddr = Address.fromInt(ADDR_HEAP_BUCKETS_START).add(availableBucket << SIZEOF_PTR_SH);
Address chunkPtr = bucketStartAddr.getAddress();
int chunkSize = readChunkSize(chunkPtr);
boolean bucketHasMultipleChunks = false;
Address nextStart = readChunkNextFreeAddr(chunkPtr);
if(nextStart.toInt() != 0) {
// there is another free chunk in the bucket that comes after this chunk,
// make the next free chunk in the list the first free chunk
bucketStartAddr.putAddress(nextStart);
writeChunkPrevFreeAddr(nextStart, Address.fromInt(0));
}else {
// there are no remaining free chunks in the bucket
// clear the bit in the bucket bitmask
bucketMask = (bucketMask ^ (1L << bucket));
Address.fromInt(ADDR_HEAP_BUCKETS_FREE_MASK).putLong(bucketMask);
// check if the first chunk in the bucket is large enough
if(chunkSize - 8 < sizeBytes) { // size - 2 ints
// set bucket start chunk pointer to null
bucketStartAddr.putAddress(Address.fromInt(0));
// the chunk is not large enough, move the first chunk to the end of the list
// and then check in the next bucket (where the chunks are definitely large enough)
// this functionality is present in emmalloc (emscripten)
Address chunkNextPtr = readChunkNextFreeAddr(chunkPtr);
if(chunkNextPtr.getInt() != chunkPtr.getInt()) {
bucketStartAddr.putAddress(chunkNextPtr);
chunkPtr = chunkNextPtr;
bucketHasMultipleChunks = true;
}
// mark the chunk in use
setChunkInUse(chunkPtr, true);
// extend mask to the next bucket
bucketMask = (bucketMask & (0xFFFFFFFFFFFFFFFFL << (bucket + 1)));
// return the chunk we just removed from the list, +4 bytes to skip size
if(bucketMask != 0l) {
// there is a bucket with a larger chunk
int availableLargerBucket = numberOfTrailingZerosL(bucketMask);
Address largerBucketStartAddr = Address.fromInt(ADDR_HEAP_BUCKETS_START).add(availableLargerBucket << SIZEOF_PTR_SH);
Address largerChunkPtr = largerBucketStartAddr.getAddress();
int largerChunkSize = readChunkSize(largerChunkPtr);
// this will remove the chunk from the free list
allocateMemoryFromChunk(largerChunkPtr, largerChunkSize, sizeBytes);
// +4 bytes to skip size int
Address ret = largerChunkPtr.add(4);
// clear if requested
if(cleared) {
Allocator.fillZero(ret, sizeBytes);
}
return ret;
}
}else {
// the first chunk in the bucket is large enough
// this will remove the chunk from the free list
allocateMemoryFromChunk(chunkPtr, chunkSize, sizeBytes);
// +4 bytes to skip size int
Address ret = chunkPtr.add(4);
// clear if requested
if(cleared) {
Allocator.fillZero(ret, sizeBytes);
}
return ret;
}
if(bucketHasMultipleChunks) {
// if we've reached this point, it means the first chunk in the bucket wasn't large enough
// and there weren't any chunks in the larger buckets we could split up
// so we need to look closer
// iterate the (only) bucket of possibly large enough chunks
Address addrIterator = chunkPtr;
while((addrIterator = readChunkNextFreeAddr(addrIterator)).getInt() != chunkPtr.getInt()) {
chunkSize = readChunkSize(addrIterator);
// check if the chunk is large enough
if(chunkSize - 8 >= sizeBytes) { // size - 2 ints
// we've found a large enough chunk
// this will remove the chunk from the free list
allocateMemoryFromChunk(addrIterator, chunkSize, sizeBytes);
// +4 bytes to skip size int
Address ret = chunkPtr.add(4);
// clear if requested
@ -191,9 +204,76 @@ public final class LaxMalloc {
return ret;
}
}
}
// no other options, time to sbrk
int sizePlusInts = sizeBytes + 8; // size + 2 ints
Address newChunk = growHeap(sizePlusInts); // sbrk
// Out of memory
if(newChunk.toInt() == 0) {
return Address.fromInt(0); //TODO
}
// provision the new chunk
newChunk.putInt(sizePlusInts | 0x80000000); // size + in use flag
newChunk.add(sizeBytes + 4).putInt(sizePlusInts); // size integer at the end
// return the chunk, +4 bytes to skip size int
// we don't need to clear it because its new memory
return newChunk.add(4);
}
private static Address laxHugeAlloc(int sizeBytes, boolean cleared) {
return null; //TODO: bucket number 63
// check the bucket mask if bucket 63 has any chunks
if((Address.fromInt(ADDR_HEAP_BUCKETS_FREE_MASK).getLong() & 0x8000000000000000L) != 0) {
// bucket 63 address
Address bucketStartAddr = Address.fromInt(ADDR_HEAP_BUCKETS_START).add(63 << SIZEOF_PTR_SH);
Address chunkPtr = bucketStartAddr.getAddress();
// iterate all free huge chunks
Address addrIterator = chunkPtr;
while((addrIterator = readChunkNextFreeAddr(addrIterator)).getInt() != chunkPtr.getInt()) {
int chunkSize = readChunkSize(addrIterator);
if(chunkSize - 8 >= sizeBytes) { // size - 2 ints
// we've found a large enough chunk
// this will remove the chunk from the free list
allocateMemoryFromChunk(addrIterator, chunkSize, sizeBytes);
// +4 bytes to skip size int
Address ret = chunkPtr.add(4);
// clear if requested
if(cleared) {
Allocator.fillZero(ret, sizeBytes);
}
return ret;
}
}
}
// no free huge chunks found, time to sbrk
int sizePlusInts = sizeBytes + 8; // size + 2 ints
Address newChunk = growHeap(sizePlusInts); // sbrk
// Out of memory
if(newChunk.toInt() == 0) {
return Address.fromInt(0); //TODO
}
// provision the new chunk
newChunk.putInt(sizePlusInts | 0x80000000); // size + in use flag
newChunk.add(sizeBytes + 4).putInt(sizePlusInts); // size integer at the end
// return the chunk, +4 bytes to skip size int
// we don't need to clear it because its new memory
return newChunk.add(4);
}
/**
@ -229,7 +309,7 @@ public final class LaxMalloc {
chunkPtr = prevChunkPtr;
chunkSize += prevChunkSize;
chunkPtr.putInt(chunkSize);
chunkPtr.add(chunkSize).putInt(chunkSize);
chunkPtr.add(chunkSize - 4).putInt(chunkSize);
}
}
@ -246,7 +326,7 @@ public final class LaxMalloc {
// resize the current chunk to also contain the next chunk
chunkSize += nextChunkSize;
chunkPtr.putInt(chunkSize);
chunkPtr.add(chunkSize).putInt(chunkSize);
chunkPtr.add(chunkSize - 4).putInt(chunkSize);
}
}
@ -254,6 +334,44 @@ public final class LaxMalloc {
linkChunkInFreeList(chunkPtr, chunkSize);
}
/**
* Allocates memory from a free chunk, if the allocSize is smaller than the chunkSize by
* enough of a margin then the chunk is split into two smaller chunks, and the upper part
* of the chunk is returned to a bucket of free chunks
*/
private static void allocateMemoryFromChunk(Address chunkPtr, int chunkSize, int allocSize) {
// remove the chunk from its bucket
unlinkChunkFromFreeList(chunkPtr, chunkSize);
int otherHalfSize = chunkSize - allocSize - 8; // -size - 2 ints
// check if we can split the chunk into two smaller chunks
// chunk must be large enough to hold the 2 list pointers
if(otherHalfSize - (2 << SIZEOF_PTR_SH) >= MIN_ALLOC_SIZE) {
// chunk is large enough to split
// provision the lower part of the chunk, the part we want to use
int sizePlusInts = allocSize + 8; // size + 2 ints
chunkPtr.putInt(sizePlusInts | 0x80000000); // size + in use flag
chunkPtr.add(allocSize + 4).putInt(sizePlusInts); // size integer at the end
// provision the upper part of the chunk that we want to return to the free list
Address otherChunkPtr = chunkPtr.add(sizePlusInts);
otherChunkPtr.putInt(otherHalfSize); // size
otherChunkPtr.add(otherHalfSize - 4).putInt(otherHalfSize); // size (end)
// return the upper part of the chunk to the free chunks list
linkChunkInFreeList(otherChunkPtr, otherHalfSize);
}else {
// not large enough to split, just take the entire chunk
setChunkInUse(chunkPtr, true);
}
}
/**
* Adds a free chunk to its corresponding bucket
*/
private static void linkChunkInFreeList(Address chunkPtr, int chunkSize) {
int bucket = getListBucket(chunkSize - 8); // size - 2 ints
@ -262,27 +380,43 @@ public final class LaxMalloc {
// test the bucket mask if the bucket is empty
if((bucketMask & (1L << bucket)) == 0l) {
// bucket is empty, add the free chunk to the list
bucketStartAddr.putAddress(chunkPtr);
writeChunkPrevFreeAddr(chunkPtr, Address.fromInt(0));
writeChunkNextFreeAddr(chunkPtr, Address.fromInt(0));
writeChunkPrevFreeAddr(chunkPtr, chunkPtr);
writeChunkNextFreeAddr(chunkPtr, chunkPtr);
// set the free bit in bucket mask
bucketMask |= (1L << bucket);
Address.fromInt(ADDR_HEAP_BUCKETS_FREE_MASK).putLong(bucketMask);
}else {
// bucket is not empty, append to the bucket's existing free chunks list
Address otherBucketStart = bucketStartAddr.getAddress();
writeChunkPrevFreeAddr(otherBucketStart, chunkPtr);
Address otherBucketPrev = readChunkPrevFreeAddr(otherBucketStart);
// link new chunk to the existing chunks in the bucket
writeChunkPrevFreeAddr(chunkPtr, otherBucketPrev);
writeChunkNextFreeAddr(chunkPtr, otherBucketStart);
writeChunkPrevFreeAddr(chunkPtr, Address.fromInt(0));
// link the existing chunks in the bucket to the new chunk
writeChunkPrevFreeAddr(otherBucketStart, chunkPtr);
writeChunkNextFreeAddr(otherBucketPrev, chunkPtr);
// put the chunk in the bucket
bucketStartAddr.putAddress(chunkPtr);
}
}
/**
* Removes a free chunk from its corresponding bucket
*/
private static void unlinkChunkFromFreeList(Address chunkPtr, int chunkSize) {
Address prevChunkPtr = readChunkPrevFreeAddr(chunkPtr);
Address nextChunkPtr = readChunkNextFreeAddr(chunkPtr);
if((prevChunkPtr.toInt() | nextChunkPtr.toInt()) == 0) {
if(prevChunkPtr.toInt() == nextChunkPtr.toInt()) {
// chunk is the only one currently in its bucket
int chunkBucket = getListBucket(chunkSize - 8); // size - 2 ints
@ -298,36 +432,22 @@ public final class LaxMalloc {
}else {
// there are other chunks in this bucket
if(prevChunkPtr.toInt() != 0) {
// previous chunk exists
if(nextChunkPtr.toInt() != 0) {
// next chunk exits, link it to the previous chunk
// link the next chunk to the previous chunk
writeChunkNextFreeAddr(prevChunkPtr, nextChunkPtr);
writeChunkPrevFreeAddr(nextChunkPtr, prevChunkPtr);
}else {
// there is no next chunk
writeChunkNextFreeAddr(prevChunkPtr, Address.fromInt(0));
}
}else {
// no previous chunk, this must be the first chunk in the bucket
int chunkBucket = getListBucket(chunkSize - 8); // size - 2 ints
Address bucketStartAddr = Address.fromInt(ADDR_HEAP_BUCKETS_START).add(chunkBucket << SIZEOF_PTR_SH);
Address bucketStartChunk = bucketStartAddr.getAddress();
// we already know the next chunk exists
// make the next chunk the first chunk in the bucket
// chunk is the first in the bucket, so we also need to
// update the bucket to point to the next chunk instead
if(bucketStartChunk.toInt() == chunkPtr.toInt()) {
bucketStartAddr.putAddress(nextChunkPtr);
// unlink the next chunk from the current chunk
writeChunkPrevFreeAddr(nextChunkPtr, Address.fromInt(0));
}
}
}
private static final int NUM_FREE_BUCKETS = 64;
/**
* https://github.com/emscripten-core/emscripten/blob/16a0bf174cb85f88b6d9dcc8ee7fbca59390185b/system/lib/emmalloc.c#L241
* (MIT License)
@ -338,7 +458,7 @@ public final class LaxMalloc {
int clz = numberOfLeadingZerosI(allocSize);
int bucketIndex = (clz > 19) ? 110 - (clz << 2) + ((allocSize >> (29 - clz)) ^ 4)
: min(71 - (clz << 1) + ((allocSize >> (30 - clz)) ^ 2), NUM_FREE_BUCKETS - 1);
: min(71 - (clz << 1) + ((allocSize >> (30 - clz)) ^ 2), 63);
return bucketIndex;
}