/// <summary>
/// Creates a segment that stores data in local memory array byte buffers
/// </summary>
internal override DefaultPileBase._segment MakeSegment(int segmentNumber)
{
var memory = new LocalMemory(SegmentSize);
var result = new _segment(this, memory, true);
return(result);
}
private bool advanceBuffer()
{
var segs = m_Pile.m_Segments;
if (segs.Count == 0)
{
return(false);
}
m_BufferIdx = -1;
m_Buffer.Clear();
while (true)
{
_segment seg = null;
while (m_SegmentIdx < segs.Count)
{
seg = segs[m_SegmentIdx];
if (seg == null || Thread.VolatileRead(ref seg.DELETED) != 0)
{
m_SegmentIdx++;
m_Address = 0;
}
else
{
break;
}
}
if (seg == null)
{
return(m_Buffer.Count > 0);
}
if (!m_Pile.getReadLock(seg))
{
return(false);
}
try
{
var eof = crawlSegment(seg);
if (eof)
{
m_SegmentIdx++;
m_Address = 0;
continue;
}
return(true);
}
finally
{
m_Pile.releaseReadLock(seg);
}
}
}
private bool crawlSegment(_segment seg)//must be called under segment read lock
{
const int BUFFER_SIZE = 1024;
var addr = 0;//start crawling from very first byte to avoid segment corruption as previous address may have been deleted
while (addr < seg.Data.Length - CHUNK_HDER_SZ)
{
var add = addr >= m_Address;
var chunkStartAdr = addr;
var flag = seg.Data.ReadChunkFlag(addr);
if (flag == ChunkFlag.Wrong) //todo In future corruption recovery attempt may take place if we scan form 8-aligned block
{
throw new PileException(StringConsts.PILE_CRAWL_INTERNAL_SEGMENT_CORRUPTION_ERROR.Args(addr));
}
addr += 3;
var payloadSize = seg.Data.ReadInt32(addr); addr += 4;
var sver = seg.Data.ReadByte(addr); addr++; //read serializer version
addr += payloadSize; //skip the body of payload
if (!add)
{
continue;
}
m_Address = addr;//next chunk
if (flag == ChunkFlag.Used)
{
var ptr = new PilePointer(m_SegmentIdx, chunkStartAdr);
var dt = sver == SVER_UTF8 ? PileEntry.DataType.String :
sver == SVER_BUFF ? PileEntry.DataType.Buffer :
sver == SVER_LINK ? PileEntry.DataType.Link : PileEntry.DataType.Object;
var entry = new PileEntry(ptr, dt, payloadSize);
m_Buffer.Add(entry);
if (m_Buffer.Count == BUFFER_SIZE)
{
return(m_Address >= seg.Data.Length - CHUNK_HDER_SZ);
}
}
}//while
return(true);
}
/// <summary>
/// Puts a CLR object into the pile and returns a newly-allocated pointer.
/// Throws out-of-space if there is not enough space in the pile and limits are set.
/// Optional lifeSpanSec is ignored by this implementation
/// </summary>
public PilePointer Put(object obj, uint lifeSpanSec = 0)
{
if (!Running) return PilePointer.Invalid;
if (obj==null) throw new PileException(StringConsts.ARGUMENT_ERROR+GetType().Name+".Put(obj==null)");
Interlocked.Increment(ref m_stat_PutCount);
//1 serialize to determine the size
int serializedSize;
byte serializerVersion;
var buffer = serialize(obj, out serializedSize, out serializerVersion);
var payloadSize = IntMath.Align8(serializedSize);
var chunkSize = CHUNK_HDER_SZ + payloadSize;
if (chunkSize>m_SegmentSize)
throw new PileOutOfSpaceException(StringConsts.PILE_OBJECT_LARGER_SEGMENT_ERROR.Args(payloadSize));
while(true)
{
if (!Running) return PilePointer.Invalid;
var segs = m_Segments;
for(var idxSegment=0; idxSegment<segs.Count; idxSegment++)
{
var seg = segs[idxSegment];
if (seg==null) continue;
if (seg.DELETED!=0) continue;
var sused = seg.UsedBytes;
if (seg.FreeCapacity > chunkSize)
{
if (!getWriteLock(seg)) return PilePointer.Invalid;
try
{
if (Thread.VolatileRead(ref seg.DELETED)==0 && seg.FreeCapacity > chunkSize)
{
var adr = seg.Allocate(buffer, payloadSize, serializerVersion);
if (adr>=0) return new PilePointer(idxSegment, adr);//allocated before crawl
var utcNow = DateTime.UtcNow;
if ((utcNow - seg.LastCrawl).TotalSeconds > (m_AllocMode==AllocationMode.FavorSpeed ? 30 : 5))
{
//could not fit, try to reclaim
seg.Crawl();
seg.LastCrawl = utcNow;
//try again
adr = seg.Allocate(buffer, payloadSize, serializerVersion);
if (adr>=0) return new PilePointer(idxSegment, adr);//allocated after crawl
}
//if we are here - still could not allocate, will try next segment in iteration
}
}
finally
{
releaseWriteLock(seg);
}
}
}//for
//if we are here, we still could not allocate space of existing segments
if (m_AllocMode==AllocationMode.FavorSpeed) break;
var nsegs = m_Segments;
if (segs.Count >= nsegs.Count) break;//if segment list grew already, repeat the whole thing again as more space may have become available
}//while
//allocate segment
lock(m_SegmentsLock)
{
if (
(m_MaxMemoryLimit>0 && AllocatedMemoryBytes+m_SegmentSize > m_MaxMemoryLimit )||
(m_MaxSegmentLimit>0 && (m_Segments.Count( s => s!=null ) + 1) > m_MaxSegmentLimit )
)
throw new PileOutOfSpaceException(StringConsts.PILE_OUT_OF_SPACE_ERROR.Args(m_MaxMemoryLimit, m_MaxSegmentLimit, m_SegmentSize));
var newSeg = new _segment(this);
var newSegs = new List<_segment>(m_Segments);
newSegs.Add( newSeg );
var adr = newSeg.Allocate(buffer, payloadSize, serializerVersion);
var pp = new PilePointer(newSegs.Count-1, adr);
m_Segments = newSegs;
return pp;
}
}
private void releaseWriteLock(_segment segment)
{
segment.RWSynchronizer.ReleaseWriteLock();
}
//the writer lock allows only 1 writer at a time that conflicts with a single reader
private bool getWriteLock(_segment segment)
{
return segment.RWSynchronizer.GetWriteLock((_) => !this.Running);
}
private void releaseWriteLock(_segment segment)
{
Thread.VolatileWrite(ref segment.LCK_READERS, 0L);
}
//the writer lock allows only 1 writer at a time that conflicts with a single reader
private bool getWriteLock(_segment segment)
{
long spinCount = 0;
var tightWait = Interlocked.Increment(ref segment.LCK_WAITING_WRITERS) < CPU_COUNT;
while(Interlocked.CompareExchange(ref segment.LCK_READERS, long.MinValue, 0)!=0)
{
if (tightWait)
{
if (spinCount<10000)
{
Thread.SpinWait(500);
spinCount++;
continue;
}
if (spinCount<12000)
{
if (!Thread.Yield()) Thread.SpinWait(1000);
spinCount++;
continue;
}
}
if (!this.Running)
{
Interlocked.Decrement(ref segment.LCK_WAITING_WRITERS);
return false;//lock failed
}
Thread.Sleep(10 + (Thread.CurrentThread.GetHashCode() & 0xf));
spinCount++;
}
Interlocked.Decrement(ref segment.LCK_WAITING_WRITERS);
return true;//lock taken
}
private void releaseReadLock(_segment segment)
{
Interlocked.Decrement(ref segment.LCK_READERS);
}
//the reader lock allows to have many readers but only 1 writer
private bool getReadLock(_segment segment)
{
//Since there are 2^63 positive combinations, even if the system has 1000 real threads that all physically execute at the same time (will never happen),
//there are 100 10-ms intervals a second = 1000 threads * 100 intervals * 60 sec = 6,000,000 increments a minute in the worst case (out of 2^63)
//which means that LCK_READERS will take around 2 million years to reach ZERO
long spinCount = 0;
while(Interlocked.Increment(ref segment.LCK_READERS)<=0)
{
if (spinCount<12000)
{
var tightWait = Thread.VolatileRead(ref segment.LCK_WAITING_WRITERS) < CPU_COUNT;
if (tightWait)
{
if (spinCount>10000)
if (!Thread.Yield()) Thread.SpinWait(1000);
else
Thread.SpinWait(500);
spinCount++;
continue;
}
}
//severe contention
if (!this.Running) return false;//lock failed
Thread.Sleep(10 + (Thread.CurrentThread.GetHashCode() & 0xf));
spinCount++;
}//while
return true;//lock taken
}
