/*
* alloc_prep_block -- (internal) prepares a memory block for allocation
*
* Once the block is fully reserved and it's guaranteed that no one else will
* be able to write to this memory region it is safe to write the allocation
* header and call the object construction function.
*
* Because the memory block at this stage is only reserved in transient state
* there's no need to worry about fail-safety of this method because in case
* of a crash the memory will be back in the free blocks collection.
*/
static int
alloc_prep_block(struct palloc_heap *heap, struct memory_block m,
palloc_constr constructor, void *arg, uint64_t *offset_value)
{
void *block_data = heap_get_block_data(heap, m);
void *userdatap = (char *)block_data + ALLOC_OFF;
uint64_t unit_size = MEMBLOCK_OPS(AUTO, &m)->
block_size(&m, heap->layout);
uint64_t real_size = unit_size * m.size_idx;
ASSERT((uint64_t)block_data % ALLOC_BLOCK_SIZE == 0);
ASSERT((uint64_t)userdatap % ALLOC_BLOCK_SIZE == 0);
/* mark everything (including headers) as accessible */
VALGRIND_DO_MAKE_MEM_UNDEFINED(block_data, real_size);
/* mark space as allocated */
VALGRIND_DO_MEMPOOL_ALLOC(heap->layout, userdatap,
real_size - ALLOC_OFF);
alloc_write_header(heap, block_data, m, real_size);
int ret;
if (constructor != NULL &&
(ret = constructor(heap->base, userdatap,
real_size - ALLOC_OFF, arg)) != 0) {
/*
* If canceled, revert the block back to the free state in vg
* machinery. Because the free operation is only performed on
* the user data, the allocation header is made inaccessible
* in a separate call.
*/
VALGRIND_DO_MEMPOOL_FREE(heap->layout, userdatap);
VALGRIND_DO_MAKE_MEM_NOACCESS(block_data, ALLOC_OFF);
/*
* During this method there are several stores to pmem that are
* not immediately flushed and in case of a cancellation those
* stores are no longer relevant anyway.
*/
VALGRIND_SET_CLEAN(block_data, ALLOC_OFF);
return ret;
}
/* flushes both the alloc and oob headers */
pmemops_persist(&heap->p_ops, block_data, ALLOC_OFF);
/*
* To avoid determining the user data pointer twice this method is also
* responsible for calculating the offset of the object in the pool that
* will be used to set the offset destination pointer provided by the
* caller.
*/
*offset_value = PMALLOC_PTR_TO_OFF(heap, userdatap);
return 0;
}
/*
* get_mblock_from_alloc -- (internal) returns allocation memory block
*/
static struct memory_block
get_mblock_from_alloc(struct palloc_heap *heap,
struct allocation_header *alloc)
{
struct memory_block m = {
alloc->chunk_id,
alloc->zone_id,
0,
0
};
uint64_t unit_size = MEMBLOCK_OPS(AUTO, &m)->
block_size(&m, heap->layout);
m.block_off = MEMBLOCK_OPS(AUTO, &m)->block_offset(&m, heap, alloc);
m.size_idx = CALC_SIZE_IDX(unit_size, alloc->size);
return m;
}
/*
* run_block_offset -- calculates the block offset based on the number of bytes
* between the beginning of the chunk and the allocation data.
*
* Because the block offset is not represented in bytes but in 'unit size',
* the number of bytes must also be divided by the chunks block size.
* A non-zero remainder would mean that either the caller provided incorrect
* pointer or the allocation algorithm created an invalid allocation block.
*/
static uint16_t
run_block_offset(struct memory_block *m, struct palloc_heap *heap, void *ptr)
{
size_t block_size = MEMBLOCK_OPS(RUN, &m)->block_size(m, heap->layout);
void *data = heap_get_block_data(heap, *m);
uintptr_t diff = (uintptr_t)ptr - (uintptr_t)data;
ASSERT(diff <= RUNSIZE);
ASSERT((size_t)diff / block_size <= UINT16_MAX);
ASSERT(diff % block_size == 0);
uint16_t block_off = (uint16_t)((size_t)diff / block_size);
return block_off;
}
/*
* palloc_operation -- persistent memory operation. Takes a NULL pointer
* or an existing memory block and modifies it to occupy, at least, 'size'
* number of bytes.
*
* The malloc, free and realloc routines are implemented in the context of this
* common operation which encompasses all of the functionality usually done
* separately in those methods.
*
* The first thing that needs to be done is determining which memory blocks
* will be affected by the operation - this varies depending on the whether the
* operation will need to modify or free an existing block and/or allocate
* a new one.
*
* Simplified allocation process flow is as follows:
* - reserve a new block in the transient heap
* - prepare the new block
* - create redo log of required modifications
* - chunk metadata
* - offset of the new object
* - commit and process the redo log
*
* And similarly, the deallocation process:
* - create redo log of required modifications
* - reverse the chunk metadata back to the 'free' state
* - set the destination of the object offset to zero
* - commit and process the redo log
* - return the memory block back to the free blocks transient heap
*
* Reallocation is a combination of the above, which one additional step
* of copying the old content in the meantime.
*/
int
palloc_operation(struct palloc_heap *heap,
uint64_t off, uint64_t *dest_off, size_t size,
palloc_constr constructor, void *arg,
struct operation_context *ctx)
{
struct bucket *b = NULL;
struct allocation_header *alloc = NULL;
struct memory_block existing_block = {0, 0, 0, 0};
struct memory_block new_block = {0, 0, 0, 0};
struct memory_block reclaimed_block = {0, 0, 0, 0};
int ret = 0;
/*
* These two lock are responsible for protecting the metadata for the
* persistent representation of a chunk. Depending on the operation and
* the type of a chunk, they might be NULL.
*/
pthread_mutex_t *existing_block_lock = NULL;
pthread_mutex_t *new_block_lock = NULL;
size_t sizeh = size + sizeof(struct allocation_header);
/*
* The offset of an existing block can be nonzero which means this
* operation is either free or a realloc - either way the offset of the
* object needs to be translated into structure that all of the heap
* methods operate in.
*/
if (off != 0) {
alloc = ALLOC_GET_HEADER(heap, off);
existing_block = get_mblock_from_alloc(heap, alloc);
/*
* This lock must be held until the operation is processed
* successfully, because other threads might operate on the
* same bitmap value.
*/
existing_block_lock = MEMBLOCK_OPS(AUTO, &existing_block)->
get_lock(&existing_block, heap);
if (existing_block_lock != NULL)
util_mutex_lock(existing_block_lock);
#ifdef DEBUG
if (MEMBLOCK_OPS(AUTO,
&existing_block)->get_state(&existing_block, heap) !=
MEMBLOCK_ALLOCATED) {
ERR("Double free or heap corruption");
ASSERT(0);
}
#endif /* DEBUG */
/*
* The memory block must return back to the originating bucket,
* otherwise coalescing of neighbouring blocks will be rendered
* impossible.
*
* If the block was allocated in a different incarnation of the
* heap (i.e. the application was restarted) and the chunk from
* which the allocation comes from was not yet processed, the
* originating bucket does not exists and all of the otherwise
* necessary volatile heap modifications won't be performed for
* this memory block.
*/
b = heap_get_chunk_bucket(heap, alloc->chunk_id,
alloc->zone_id);
}
/* if allocation or reallocation, reserve new memory */
if (size != 0) {
/* reallocation to exactly the same size, which is a no-op */
if (alloc != NULL && alloc->size == sizeh)
goto out;
errno = alloc_reserve_block(heap, &new_block, sizeh);
if (errno != 0) {
ret = -1;
goto out;
}
}
/*
* The offset value which is to be written to the destination pointer
* provided by the caller.
*/
uint64_t offset_value = 0;
/* lock and persistently free the existing memory block */
if (!MEMORY_BLOCK_IS_EMPTY(existing_block)) {
/*
* This method will insert new entries into the operation
* context which will, after processing, update the chunk
* metadata to 'free' - it also takes care of all the necessary
* coalescing of blocks.
* Even though the transient state of the heap is used during
* this method to locate neighbouring blocks, it isn't modified.
*
* The rb block is the coalesced memory block that the free
* resulted in, to prevent volatile memory leak it needs to be
* inserted into the corresponding bucket.
*/
reclaimed_block = heap_free_block(heap, b, existing_block, ctx);
offset_value = 0;
}
if (!MEMORY_BLOCK_IS_EMPTY(new_block)) {
if (alloc_prep_block(heap, new_block, constructor,
arg, &offset_value) != 0) {
/*
* Constructor returned non-zero value which means
* the memory block reservation has to be rolled back.
*/
struct bucket *new_bucket = heap_get_chunk_bucket(heap,
new_block.chunk_id, new_block.zone_id);
ASSERTne(new_bucket, NULL);
/*
* Omitting the context in this method results in
* coalescing of blocks without affecting the persistent
* heap state.
*/
new_block = heap_free_block(heap, new_bucket,
new_block, NULL);
CNT_OP(new_bucket, insert, heap, new_block);
if (new_bucket->type == BUCKET_RUN)
heap_degrade_run_if_empty(heap,
new_bucket, new_block);
errno = ECANCELED;
ret = -1;
goto out;
}
/*
* This lock must be held for the duration between the creation
* of the allocation metadata updates in the operation context
* and the operation processing. This is because a different
* thread might operate on the same 8-byte value of the run
* bitmap and override allocation performed by this thread.
*/
new_block_lock = MEMBLOCK_OPS(AUTO, &new_block)->
get_lock(&new_block, heap);
/* the locks might be identical in the case of realloc */
if (new_block_lock == existing_block_lock)
new_block_lock = NULL;
if (new_block_lock != NULL)
util_mutex_lock(new_block_lock);
#ifdef DEBUG
if (MEMBLOCK_OPS(AUTO,
&new_block)->get_state(&new_block, heap) !=
MEMBLOCK_FREE) {
ERR("Double free or heap corruption");
ASSERT(0);
}
#endif /* DEBUG */
/*
* The actual required metadata modifications are chunk-type
* dependent, but it always is a modification of a single 8 byte
* value - either modification of few bits in a bitmap or
* changing a chunk type from free to used.
*/
MEMBLOCK_OPS(AUTO, &new_block)->prep_hdr(&new_block,
heap, MEMBLOCK_ALLOCATED, ctx);
}
/* not in-place realloc */
if (!MEMORY_BLOCK_IS_EMPTY(existing_block) &&
!MEMORY_BLOCK_IS_EMPTY(new_block)) {
size_t old_size = alloc->size;
size_t to_cpy = old_size > sizeh ? sizeh : old_size;
VALGRIND_ADD_TO_TX(PMALLOC_OFF_TO_PTR(heap, offset_value),
to_cpy - ALLOC_OFF);
pmemops_memcpy_persist(&heap->p_ops,
PMALLOC_OFF_TO_PTR(heap, offset_value),
PMALLOC_OFF_TO_PTR(heap, off),
to_cpy - ALLOC_OFF);
VALGRIND_REMOVE_FROM_TX(PMALLOC_OFF_TO_PTR(heap, offset_value),
to_cpy - ALLOC_OFF);
}
/*
* If the caller provided a destination value to update, it needs to be
* modified atomically alongside the heap metadata, and so the operation
* context must be used.
* The actual offset value depends on whether the operation type.
*/
if (dest_off != NULL)
operation_add_entry(ctx, dest_off, offset_value, OPERATION_SET);
operation_process(ctx);
/*
* After the operation succeeded, the persistent state is all in order
* but in some cases it might not be in-sync with the its transient
* representation.
*/
if (!MEMORY_BLOCK_IS_EMPTY(existing_block)) {
VALGRIND_DO_MEMPOOL_FREE(heap->layout,
(char *)heap_get_block_data(heap, existing_block)
+ ALLOC_OFF);
/* we might have been operating on inactive run */
if (b != NULL) {
/*
* Even though the initial condition is to check
* whether the existing block exists it's important to
* use the 'reclaimed block' - it is the coalesced one
* and reflects the current persistent heap state,
* whereas the existing block reflects the state from
* before this operation started.
*/
CNT_OP(b, insert, heap, reclaimed_block);
/*
* Degrading of a run means turning it back into a chunk
* in case it's no longer needed.
* It might be tempting to defer this operation until
* such time that the chunk is actually needed, but
* right now the decision is to keep the persistent heap
* state as clean as possible - and that means not
* leaving unused data around.
*/
if (b->type == BUCKET_RUN)
heap_degrade_run_if_empty(heap, b,
reclaimed_block);
}
}
out:
if (new_block_lock != NULL)
util_mutex_unlock(new_block_lock);
if (existing_block_lock != NULL)
util_mutex_unlock(existing_block_lock);
return ret;
}
