High CPU usage during 15 acquiring analog input and write to file (suggestion needed)

Question

Helllo everybody,
      I have a problem about the usage of CPU now i am using a realtime target (PXI-8186) with Daq (PXI-6259) to get 15 analog signals at the rate of 10kHz
at first i try to get signal at different rate but i found out that all of the channels share the same clock so i get the highest frequency that i desired  after that i do 
some data manipulation with displaying charts  and use shift register to stack data in array of string  finally i write the data to spreadsheet every  5 second, by doing this the CPU usage
is always 100% and reduce by the time the file is recordedto 71% or so and then start to increase to 100% again. I think  the things that make CPU usage too high are
1. Time loop: because i set the period to be 10ms maybe this is too low.
2. The shift registered: may be it use too much overhead memory but i do not know other method to stack data before writing to a file 
3. RAM too low: The RAM of PXI is only 256mb
4. Poor program arrangement: Because i am new to labview the program is not arranging correctly or i may use some inappropriate structure.
My program is very messy sorry about it because i avoid using SubVI and i am new to labview. Please help any suggestion is apperciated. Thanks in advance.
Best regard
Wuttikrai
Attachments:
target save.vi ‏328 KB

Answer 1

It looks like you are writing your data to disk every so often.  For that reason, I recommend making it based on the number of samples you have instead of the time.  With that you can preallocate your arrays with constants going into the shift registers.  You then use Replace Array Subset to update your arrays.  When you write to the file, make sure you go back to overwriting the beginning of your array.  This will greatly reduce the amount of time you spend reallocating memory and will reduce your memory usage.
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