void* AllocPool::Alloc(size_t inReqSize)
{
#ifdef DISABLE_MEMORY_POOLS
return malloc(inReqSize);
#endif
// OK it has a lot of gotos, but these remove a whole lot of common code
// that was obfuscating the original version of this function.
// So here I am choosing the OnceAndOnlyOnce principle over the caveats on gotos.
// The gotos only jump forward and only to the exit paths of the function
// The old bin block scheme has been replaced by 4 x 32 bit words so that each bin has a bit
// and the next bin is found using a count leading zeroes instruction. Much faster.
// Also now each bin's flag can be kept accurate. This simplifies the searching code quite a bit.
// Also fwiw, changed 'victim' in the original code to 'candidate'. 'victim' just bothered me.
AllocChunkPtr candidate; /* inspected/selected chunk */
size_t candidate_size; /* its size */
AllocChunkPtr remainder; /* remainder from a split */
int32 remainder_size; /* its size */
AllocAreaPtr area;
size_t areaSize;
size_t size = RequestToSize(inReqSize);
int index = BinIndex(size);
assert(index < 128);
AllocChunkPtr bin = mBins + index;
check_pool();
/* Check for exact match in a bin */
if (index < kMaxSmallBin) { /* Faster version for small requests */
/* No traversal or size check necessary for small bins. */
candidate = bin->Prev();
/* Also scan the next one, since it would have a remainder < kMinAllocSize */
if (candidate == bin) candidate = (++bin)->Prev();
if (candidate != bin) {
candidate_size = candidate->Size();
goto found_exact_fit;
}
index += 2; /* Set for bin scan below. We've already scanned 2 bins. */
} else {
for (candidate = bin->Prev(); candidate != bin; candidate = candidate->Prev()) {
candidate_size = candidate->Size();
remainder_size = (int)(candidate_size - size);
if (remainder_size >= (int32)kMinAllocSize) { /* too big */
--index; /* adjust to rescan below after checking last remainder */
break;
} else if (remainder_size >= 0) { /* exact fit */
goto found_exact_fit;
}
}
++index;
}
for(; (index = NextFullBin(index)) >= 0; ++index) {
bin = mBins + index;
/* Find and use first big enough chunk ... */
for (candidate = bin->Prev(); candidate != bin; candidate = candidate->Prev()) {
candidate_size = candidate->Size();
remainder_size = (int)(candidate_size - size);
if (remainder_size >= (int32)kMinAllocSize) { /* split */
UnlinkFree(candidate);
goto found_bigger_fit;
} else if (remainder_size >= 0) goto found_exact_fit;
}
}
check_pool();
if (mAreaMoreSize == 0) { /* pool has a non-growable area */
if (mAreas != NULL /* fixed size area exhausted */
|| size > mAreaInitSize) /* too big anyway */
goto found_nothing;
areaSize = mAreaInitSize;
goto split_new_area;
}
if (size > mAreaMoreSize) {
areaSize = size;
goto whole_new_area;
} else {
areaSize = mAreaMoreSize;
goto split_new_area;
}
// exit paths:
found_nothing:
//ipostbuf("alloc failed. size: %d\n", inReqSize);
throw std::runtime_error("alloc failed, increase server's memory allocation (e.g. via ServerOptions)");
whole_new_area:
//ipostbuf("whole_new_area\n");
area = NewArea(areaSize);
if (!area) return 0;
candidate = &area->mChunk;
candidate_size = candidate->Size();
goto return_chunk;
split_new_area:
//ipostbuf("split_new_area\n");
area = NewArea(areaSize);
if (!area) return 0;
candidate = &area->mChunk;
candidate_size = candidate->Size();
remainder_size = (int)(areaSize - size);
// FALL THROUGH
found_bigger_fit:
//ipostbuf("found_bigger_fit\n");
remainder = candidate->ChunkAtOffset(size);
remainder->SetSizeFree(remainder_size);
candidate_size -= remainder_size;
LinkFree(remainder);
goto return_chunk;
found_exact_fit:
check_pool();
UnlinkFree(candidate);
// FALL THROUGH
return_chunk:
candidate->SetSizeInUse(candidate_size);
check_malloced_chunk(candidate, candidate_size);
check_pool();
garbage_fill(candidate);
return candidate->ToPtr();
}
//This function is equal to mspace_malloc
//replacing PREACTION with 0 and POSTACTION with nothing
void* mspace_malloc_lockless(mspace msp, size_t bytes)
{
mstate ms = (mstate)msp;
if (!ok_magic(ms)) {
USAGE_ERROR_ACTION(ms,ms);
return 0;
}
if (!0){//PREACTION(ms)) {
void* mem;
size_t nb;
if (bytes <= MAX_SMALL_REQUEST) {
bindex_t idx;
binmap_t smallbits;
nb = (bytes < MIN_REQUEST)? MIN_CHUNK_SIZE : pad_request(bytes);
idx = small_index(nb);
smallbits = ms->smallmap >> idx;
if ((smallbits & 0x3U) != 0) { /* Remainderless fit to a smallbin. */
mchunkptr b, p;
idx += ~smallbits & 1; /* Uses next bin if idx empty */
b = smallbin_at(ms, idx);
p = b->fd;
assert(chunksize(p) == small_index2size(idx));
unlink_first_small_chunk(ms, b, p, idx);
set_inuse_and_pinuse(ms, p, small_index2size(idx));
mem = chunk2mem(p);
check_malloced_chunk(ms, mem, nb);
goto postaction;
}
else if (nb > ms->dvsize) {
if (smallbits != 0) { /* Use chunk in next nonempty smallbin */
mchunkptr b, p, r;
size_t rsize;
bindex_t i;
binmap_t leftbits = (smallbits << idx) & left_bits(idx2bit(idx));
binmap_t leastbit = least_bit(leftbits);
compute_bit2idx(leastbit, i);
b = smallbin_at(ms, i);
p = b->fd;
assert(chunksize(p) == small_index2size(i));
unlink_first_small_chunk(ms, b, p, i);
rsize = small_index2size(i) - nb;
/* Fit here cannot be remainderless if 4byte sizes */
if (SIZE_T_SIZE != 4 && rsize < MIN_CHUNK_SIZE)
set_inuse_and_pinuse(ms, p, small_index2size(i));
else {
set_size_and_pinuse_of_inuse_chunk(ms, p, nb);
r = chunk_plus_offset(p, nb);
set_size_and_pinuse_of_free_chunk(r, rsize);
replace_dv(ms, r, rsize);
}
mem = chunk2mem(p);
check_malloced_chunk(ms, mem, nb);
goto postaction;
}
else if (ms->treemap != 0 && (mem = tmalloc_small(ms, nb)) != 0) {
check_malloced_chunk(ms, mem, nb);
goto postaction;
}
}
}
