I am new to multitasking and IPC and I am trying to construct an approach for fast inter process comunication using shared memory( at first I was researching the IPC term, having in mind wcf sockets and named pipes only to eventually discover about MMF).
Now that I have successfully implemented a small test using shared memory between two processes via using Lock and EventWaitHandle signalling, I am up to an approach that implements non blocking / no-wait pattern. Now, I am trying to combine Thread.MemoryBarrier() & reading a signalling Sector from the MemoryMapedFile.
The problem is unidentified! First round goes through and second was last sited in Bermuda triangle ... out of the scope of the debugger...
say process a is sending a burst of requests for a showMsg() to process b.
//offset positions in mmf
MemoryMappedViewAccessor MmfAcc; const int opReady= 0, opCompleteRead = 4, .....
ReadTrd()
{
//[0,3] - Reader is stationed
//[4,7] - Read Complete successfully
//[8,11] - Data-size
//[12,15] - Reader-exiting
"format" the signals Section (write zeroes).
for(;;){if (WrTrd-StepMMF1 Confimed) break;}
MmfAcc- read DataSize val @offset[8]
MmfAcc- read Data val @offset[50]
MmfAcc Write exit to offset....
....heavy use of Thread.MemoryBarrier(); sets !!! (all over the place, on every shared variable...)
}
writeTrd()
{
heavy use of Thread.MemoryBarrier() !!!
//[15-19] - wr is stationed
//[20-23] - wr Complete successfully
//[24-27] - wrExiting
"format" the signals Section .
for(;;){if Reader-StepMMF1 is Confim break;}
MmfAcc- DataSize to offset[8]
write Data To offset[50] using the method below
for(;;){if Read StepMMF2 is Confim break;}
}
As I was first using the named piped solution, the Mmf approach(despite Lock and EventWaitHandle) was great performance gain compared to the namedpipe approach, but could I even go further using the above approach somehow.. ?
I could just clone this pattern like striping Raid ...
Reader1 + Reader2 & WriteThred1 + WriteThread2
so I tried it and got stuck at that point.
Is this valid approach using the full-memoryfence & sharedmemory for signalling?
If so, all is left is to see why the second iteration failed , the performance difference.
EDIT - added the logic behind the extra threads test
This is the "Bridge" I am using to manipulate writer threads (same approach for readers.
public void Write(byte[] parCurData)
{
if (ReadPosition < 0 || WritePosition < 0)
throw new ArgumentException();
this.statusSet.Add("ReadWrite:-> " + ReadPosition + "-" + WritePosition);
// var s = (FsMomitorIPCCrier)data;
////////lock (this.dataToSend)
////////{
Thread.MemoryBarrier();
LiveDataCount_CurIndex = dataQue.Where(i => i != null).Count();
this.dataQue[LiveDataCount_CurIndex] = parCurData;
Console.WriteLine("^^^^^" + Thread.CurrentThread.Name + " has Entered WritingThreads BRIDGE");
Console.WriteLine("^^^^^[transactionsQue] = {1}{0}^^^^^[dataQue.LiveDataASIndex = {2}{0}^^^^^[Current Requests Count = {3}{0}", "\r\n", Wtransactions, LiveDataCount_CurIndex, ++dataDelReqCount);
//this.itsTimeForWTrd2 = false;
if (Wtransactions != 0 && Wtransactions > ThrededSafeQ_Initial_Capcity - 1)
if (this.dataQueISFluded) this.DataQXpand();
if (itsTimeForWTrd2)
{
bool firstWt = true;
while (writerThread2Running)
{
if (!firstWt) continue;
Console.WriteLine("SECOND WRITERThread [2] is In The CoffeeCorner");
firstWt=false;
}
this.dataDelivery2 = this.dataQue[LiveDataCount_CurIndex];
Console.WriteLine("Activating SECOND WRITERThread [2]");
itsTimeForWTrd2 = false;
writerThread2Running = true;
//writerThread1Running = true;
writerThread2 = new System.Threading.Thread(WriterThread2);
writerThread2.IsBackground = true;
writerThread2.Name = this.DepoThreadName + "=[WRITER2]";
writerThread2.Start();
}
else
{
bool firstWt = true;
while (writerThread1Running)
{
if (!firstWt)continue;
Console.WriteLine("WRITERThread [1] is In The CoffeeCorner");
firstWt=false;
}
Console.WriteLine("Activating WRITERThread [1]");
this.dataDelivery1 = this.dataQue[LiveDataCount_CurIndex];
writerThread1Running = true;
writerThread1 = new System.Threading.Thread(WriterThread1);
writerThread1.IsBackground = true;
writerThread1.Name = this.DepoThreadName+"=[WRITER1]";
writerThread1.Start();
itsTimeForWTrd2 = true;
}
Thread.MemoryBarrier();
}
Using the write handle to read & write the actual data (similar code for the write)
public unsafe byte[] UsReadBytes(int offset, int num)
{
byte[] arr = new byte[num];
byte* ptr = (byte*)0;
this.accessor.SafeMemoryMappedViewHandle.AcquirePointer(ref ptr);
Marshal.Copy(IntPtr.Add(new IntPtr(ptr), offset), arr, 0, num);
this.accessor.SafeMemoryMappedViewHandle.ReleasePointer();
return arr;
}
As I said, I have researched this issue of synchronization of the data and shared memory via non blocking / no-wait / etc. Semaphores Locks so I am trying to remove any kind of overhead during the process of each transaction of data into the shared memory mapped file. I am here to ask what could be the problem eliminating the Lock And The EventWaitHandle and replacing it with the logic of memory fences and signaling through the mmf?
