/// <summary>
/// Caches a given IRP on the way down
/// </summary>
/// <param name="irp"></param>
/// <returns></returns>
public PreReadReturnCode CacheIRP(IRP irp)
{
// lookup if IRP is already cached
Dictionary<string, Dictionary<uint, FileCacheElement>> f = null;
Dictionary<uint, FileCacheElement> b = null;
FileCacheElement ce = null;
bool hit = false;
bool anyMisses = false;
FlowSLA sla = null;
ulong savedFileOffset = irp.FileOffset;
uint savedDataLength = irp.DataLength;
uint dataOffset = irp.DataOffset;
ulong fileOffset = savedFileOffset;
bool canSatisfyRequest = false;
Debug.Assert(irp.IoFlowHeader.MajorFunction == MajorFunction.IRP_MJ_READ);
if (noisyOutput)
Console.WriteLine("CacheIRP {0}: Attempting to lock cache on Offset={1} Length={2}",
Thread.CurrentThread.ManagedThreadId, fileOffset, ALIGNED_BLOCK_SIZE);
Monitor.Enter(cacheLock);
sla = FlowStats[irp.FlowId];
Debug.Assert(sla != null); //Only deal with explicitly declared flows
//Do we have enough cache space available to satisfy this request?
if (sla.FlowCacheSize > irp.DataLength)
{
canSatisfyRequest = true;
}
if (noisyOutput)
Console.WriteLine("CacheIRP {0}: Locked cache on Offset={1} Length={2}",
Thread.CurrentThread.ManagedThreadId, fileOffset, ALIGNED_BLOCK_SIZE);
if (canSatisfyRequest)
{
// iterate over all blocks
// it's a hit if all blocks are a hit, otherwise its a miss for the entire IRP
do
{
uint blockid = (uint)(fileOffset / ALIGNED_BLOCK_SIZE);
hit = false; //block isn't a hit yet
{
if (Cache.TryGetValue(irp.FlowId, out f))
{
if (f.TryGetValue(irp.IoFlow.FileName, out b))
{
if (b.TryGetValue(blockid, out ce))
{
// cache entry exists
if (noisyOutput)
Console.WriteLine("CacheIRP {0}: Attempting to lock ce on Offset={1} Length={2}",
Thread.CurrentThread.ManagedThreadId, fileOffset, ALIGNED_BLOCK_SIZE);
lock (ce.LockObj)
{
if (noisyOutput)
Console.WriteLine("CacheIRP {0}: Locked ce on Offset={1} Length={2}",
Thread.CurrentThread.ManagedThreadId, fileOffset, ALIGNED_BLOCK_SIZE);
if (ce.Data != null)
{
// real hit ; cache entry has data being read
sla = FlowStats[irp.FlowId];
Debug.Assert(sla != null); //We should always have a valid sla entry if we have a hit
hit = true;
byte[] irpData = irp.GetDataReadWrite();
Debug.Assert(ce.DataLength == ALIGNED_BLOCK_SIZE);
Buffer.BlockCopy(ce.Data, 0, irpData, (int)dataOffset, (int)ALIGNED_BLOCK_SIZE);
Debug.Assert(ce.nodeInList != null);
Debug.Assert(ce.nodeInList != null);
sla.cacheEntries.Remove(ce.nodeInList); //Assumes no duplicate ce's in the list, which should be true...
//ce.UpdateNodeList(sla.cacheEntries.AddLast(ce));
sla.cacheEntries.AddLast(ce.nodeInList);
if (sla.FlowSLAHasGhostCache())
{
sla.GhostCache.CacheReadReference(ce.fileName + Convert.ToString(blockid)); //Forward the reference to the ghost cache
}
}
else
{
// cache entry exists, BUT data is still in-flight from storage medium
hit = false;
}
}
if (noisyOutput)
Console.WriteLine("CacheIRP {0}: UnLocked ce on Offset={1} Length={2}",
Thread.CurrentThread.ManagedThreadId, fileOffset, ALIGNED_BLOCK_SIZE);
}
}
}
if (!hit)
{
// evict first
Evict(irp.FlowId);
// then insert
if (f == null)
{
Cache[irp.FlowId] = new Dictionary<string, Dictionary<uint, FileCacheElement>>();
f = Cache[irp.FlowId];
}
if (b == null)
{
f[irp.IoFlow.FileName] = new Dictionary<uint, FileCacheElement>();
b = f[irp.IoFlow.FileName];
}
if (ce == null)
{
//b[blockid] = new FileCacheElement(irp.IoFlow, irp.IoFlowRuntime.getDriveLetterFileName(irp.IoFlow.FileName), null,
// fileOffset, dataOffset, ALIGNED_BLOCK_SIZE /* copying data only */);
//string tempFileNameChunking = irp.IoFlowRuntime.getDriveLetterFileName(irp.IoFlow.FileName); //save file name here once, so we don't do multiple calls to this
b[blockid] = getFileCacheElement(irp.IoFlow, irp.IoFlow.FileName, null, fileOffset, dataOffset, ALIGNED_BLOCK_SIZE /* copying data only */);
ce = b[blockid];
// insert element into list
if (false == FlowStats.TryGetValue(irp.FlowId, out sla))
{
//sla = new FlowSLA();
//FlowStats[irp.FlowId] = sla;
Debug.Assert(0 == 1); //XXXIS let's only deal with explicitly declared flows right now
}
ce.UpdateNodeList(sla.cacheEntries.AddLast(ce));
cacheSizeUsedBytes += ALIGNED_BLOCK_SIZE;
sla.FlowCacheSizeUsedBytes += ALIGNED_BLOCK_SIZE;
if (sla.FlowSLAHasGhostCache())
{
sla.GhostCache.CacheReadReference(ce.fileName + Convert.ToString(blockid)); //Forward the reference to the ghost cache
}
}
}
}
if (noisyOutput)
Console.WriteLine("CacheIRP {0}: UnLock cache on Offset={1} Length={2}",
Thread.CurrentThread.ManagedThreadId, fileOffset, ALIGNED_BLOCK_SIZE);
fileOffset += ALIGNED_BLOCK_SIZE;
dataOffset += ALIGNED_BLOCK_SIZE;
if (hit == false)
{
anyMisses = true;
}
} while (fileOffset < savedFileOffset + savedDataLength);
if (false == FlowStats.TryGetValue(irp.FlowId, out sla))
{
Debug.Assert(0 == 1); //XXXIS let's only deal with explicitly declared flows right now
}
if (!anyMisses)
{
sla.CacheAccessesHits++; //Increment the number of hits in the cache
}
}
sla.CacheAccessesTotal++; //increment all the accesses to this cache
sla.FlowBytesAccessed += irp.DataLength;
Monitor.Exit(cacheLock);
// deal with MISSES
// Let IRP go through and intercept POST operation (with payload)
//
if (anyMisses == true || !canSatisfyRequest)
{
//Console.WriteLine("MISS: {0}", irp.FileOffset);
if (noisyOutput)
Console.WriteLine("CacheIRP {0}: PreRead MISS Offset={1} Length={2}",
Thread.CurrentThread.ManagedThreadId, irp.FileOffset, irp.DataLength);
return PreReadReturnCode.FLT_PREOP_SUCCESS_WITH_CALLBACK;
}
else
{
//Console.WriteLine("HIT: {0}", irp.FileOffset);
if (noisyOutput)
Console.WriteLine("CacheIRP {0}: PreRead HIT Offset={1} Length={2}",
Thread.CurrentThread.ManagedThreadId, irp.FileOffset, irp.DataLength);
return PreReadReturnCode.FLT_PREOP_COMPLETE;
}
}
