/// <summary>
/// Releases the given value to the pool.
/// In a few cases, the value is 'freed' instead of
/// being released to the pool. If
/// - The pool currently exceeds its max size OR
/// - If the value does not map to a bucket that's
/// currently maintained by the pool, OR
/// - If the bucket for the value exceeds its
/// maxLength, OR
/// - If the value is not recognized by the pool
/// Then, the value is 'freed'.
/// </summary>
/// <param name="value">
/// The value to release to the pool.
/// </param>
public void Release(T value)
{
Preconditions.CheckNotNull(value);
int bucketedSize = GetBucketedSizeForValue(value);
int sizeInBytes = GetSizeInBytes(bucketedSize);
lock (_poolGate)
{
Bucket <T> bucket = GetBucket(bucketedSize);
if (!InUseValues.Remove(value))
{
// This value was not 'known' to the pool (i.e.) allocated via the pool.
// Something is going wrong, so let's free the value and report soft error.
#if DEBUG_MEMORY_POOL
Debug.WriteLine($"release (free, value unrecognized) (object, size) = ({ value.GetHashCode() }, { bucketedSize })");
#endif // DEBUG_MEMORY_POOL
Free(value);
_poolStatsTracker.OnFree(sizeInBytes);
}
else
{
// free the value, if
// - Pool exceeds maxSize
// - There is no bucket for this value
// - There is a bucket for this value, but it has exceeded its maxLength
// - The value is not reusable
// If no bucket was found for the value, simply free it
// We should free the value if no bucket is found, or if the bucket length
// cap is exceeded.
// However, if the pool max size softcap is exceeded, it may not always be
// best to free *this* value.
if (bucket == null ||
bucket.IsMaxLengthExceeded() ||
IsMaxSizeSoftCapExceeded() ||
!IsReusable(value))
{
if (bucket != null)
{
bucket.DecrementInUseCount();
}
#if DEBUG_MEMORY_POOL
Debug.WriteLine($"release (free) (object, size) = ({ value.GetHashCode() }, { bucketedSize })");
#endif // DEBUG_MEMORY_POOL
Free(value);
_usedCounter.Decrement(sizeInBytes);
_poolStatsTracker.OnFree(sizeInBytes);
}
else
{
bucket.Release(value);
_freeCounter.Increment(sizeInBytes);
_usedCounter.Decrement(sizeInBytes);
_poolStatsTracker.OnValueRelease(sizeInBytes);
#if DEBUG_MEMORY_POOL
Debug.WriteLine($"release (reuse) (object, size) = ({ value.GetHashCode() }, { bucketedSize })");
#endif // DEBUG_MEMORY_POOL
}
}
LogStats();
}
}
/// <summary>
/// Gets a new 'value' from the pool, if available.
/// Allocates a new value if necessary.
/// If we need to perform an allocation,
/// - If the pool size exceeds the max-size soft cap,
/// then we attempt to trim the free portion of the pool.
/// - If the pool size exceeds the max-size hard-cap
/// (after trimming), then we throw an
/// <see cref="PoolSizeViolationException"/>.
/// Bucket length constraints are not considered in
/// this function.
/// </summary>
/// <param name="size">
/// The logical size to allocate.
/// </param>
/// <returns>A new value.</returns>
/// <exception cref="InvalidSizeException">
/// If the size of the value doesn't match the pool's
/// constraints.
/// </exception>
public T Get(int size)
{
EnsurePoolSizeInvariant();
int bucketedSize = GetBucketedSize(size);
int sizeInBytes = -1;
lock (_poolGate)
{
Bucket <T> bucket = GetBucket(bucketedSize);
if (bucket != null)
{
// Find an existing value that we can reuse
T val = bucket.Get();
if (val != null)
{
Preconditions.CheckState(InUseValues.Add(val));
// It is possible that we got a 'larger' value than we asked for.
// lets recompute size in bytes here
bucketedSize = GetBucketedSizeForValue(val);
sizeInBytes = GetSizeInBytes(bucketedSize);
_usedCounter.Increment(sizeInBytes);
_freeCounter.Decrement(sizeInBytes);
_poolStatsTracker.OnValueReuse(sizeInBytes);
LogStats();
#if DEBUG_MEMORY_POOL
Debug.WriteLine($"get (reuse) (object, size) = ({ val.GetHashCode() }, { bucketedSize })");
#endif // DEBUG_MEMORY_POOL
return(val);
}
// Fall through
}
// Check to see if we can allocate a value of the given size without
// exceeding the hard cap
sizeInBytes = GetSizeInBytes(bucketedSize);
if (!CanAllocate(sizeInBytes))
{
throw new PoolSizeViolationException(
_poolParams.MaxSizeHardCap,
_usedCounter.NumBytes,
_freeCounter.NumBytes,
sizeInBytes);
}
// Optimistically assume that allocation succeeds - if it fails, we
// need to undo those changes
_usedCounter.Increment(sizeInBytes);
if (bucket != null)
{
bucket.IncrementInUseCount();
}
}
T value = default(T);
try
{
// allocate the value outside the synchronized block, because
// it can be pretty expensive we could have done the allocation
// inside thesynchronized block, but that would have blocked out
// other operations on the pool
value = Alloc(bucketedSize);
}
catch (Exception)
{
// Assumption we made previously is not valid - allocation failed.
// We need to fix internal counters.
lock (_poolGate)
{
_usedCounter.Decrement(sizeInBytes);
Bucket <T> bucket = GetBucket(bucketedSize);
if (bucket != null)
{
bucket.DecrementInUseCount();
}
}
throw;
}
// NOTE: We checked for hard caps earlier, and then did the alloc above.
// Now we need to update state - but it is possible that a concurrent
// thread did a similar operation - with the result being that we're now
// over the hard cap. We are willing to live with that situation -
// especially since the trim call below should be able to trim back
// memory usage.
lock (_poolGate)
{
Preconditions.CheckState(InUseValues.Add(value));
// If we're over the pool's max size, try to trim the pool appropriately
TrimToSoftCap();
_poolStatsTracker.OnAlloc(sizeInBytes);
LogStats();
#if DEBUG_MEMORY_POOL
Debug.WriteLine($"get (alloc) (object, size) = ({ value.GetHashCode() }, { bucketedSize })");
#endif // DEBUG_MEMORY_POOL
}
return(value);
}
