Trying to simulate different file write speed

[tbaror]

Hello All,

I am trying to write a code that simulate write file stream with the control on speed throughput (40Mbit/s ,50Mbit/s etc ...) , and using different block size.

I have a basic code that can do full speed stream write , below example i calculating few parameters and the code
My question is that i can't figure out how to calculate sleep time between each write to achieve desired speed write?
Please advise
Thanks

40Mbit/s ==> 4.7683715820313 Mbyte/sec total 100Mbyte, block 128KB ==>0.125 Mbyte = 800IO's
4.7683715820313/0.125 = 38.1469726562504 frames per second
1000msec = 1 sec /38.1469726562504 frames = 26.21439999999973 Msec per frame write

blocksize = 128000

chunk = b'\xff'*blocksize

with open("//10.0.0.25/Software/Testfile/file.file", "wb") as f:
    seq= 0
    for num in range(1,800):

        f.write(chunk)
        f.seek(seq)
        seq = seq+blocksize
  ====> time.sleep(?)

[wavic]

Hello!
The time in time.sleep(1) means one second. So 0.001 means one ms.

[tbaror]

Hello!
The time in time.sleep(1) means one second. So 0.001 means one ms.

Thanks for the tip , i know that , i need help with formula how to calculate the amount of sleep time to achieve desired speed
Thanks

[zivoni]

You need to ensure that single loop of your for cycle takes computed time, so taking time and waiting could work:

    duration = 0.026214

    start_time = time.time()
    for num in range(1,800):        
        f.write(chunk)
        f.seek(seq)
        seq = seq+blocksize

        start_time += duration
        time.sleep(start_time - time.time())  # raise error if negative 

[tbaror]

Hi,
Thanks for the answer code :-) , i also figure out that , better using bytes than MBytes
40 Mbit/s = 41943040a bit/s = 5242880 bytes/s
128 KB = 131072 bytes
5242880 / 131072 = 40 number of blocks you can write in a second
so the delay is 1000ms/40 = 25ms so this also can be my writes sleep