Re: Fwd: Re: cpg latency

[Voznesensky Vladimir <voznesensky@xxxxxx>]

On 21.05.2012 15:34, Voznesensky Vladimir wrote:

So, every message write to the ring buffer consist of the steps:

1. If buffer_size - (write_pointer - read_pointer) % buffer_size < message_size + 1,
• set errno=EAGAIN and return;
2. If write_pointer + message_size > buf_pointer + buf_size
• write a special message to mark buffer overlimit,
• set write_pointer = buf_pointer,
• do the 1st step again and goto 3.
  
3. Write the message starting from the write pointer;
4. Write 1 to the eventfd;
5. <write pointer> += <message size>.

Every read consists of the steps:

1. Poll the file descriptors including the eventfd in the main loop, so the eventfd becomes readable;
2. Read the value from the eventfd.
3. Read the message from the buffer;
4. If the message is special,
• set read_pointer= buffer_pointer,
• do the 3d step again;
  
5. Process the message;
   
6. read_pointer += message_size;
7. If the read pointer is not equal to the write pointer,
• goto 3.
  

Am I correct here? Is my pseudocode optimal?

Opps, reading the eventfd should be done after the last step.

-- VV

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