On Sunday 15 November 2009 17:24:34 John McKown wrote:
> On Mon, 2009-11-16 at 08:22 +1000, Shane wrote:
>
> I think by I/O, the OP is saying that reading the file directly is done
> via a single read() or fread() or ... . Using a named pipe, the "cat"
> does this, but then does a write() or fwrite() to the pipe. And then his
> program does another read() or fread() to read the pipe. So, even if
> there is no physical I/O, there __is__ increased processor overhead in
> writing to and reading from the pipe. The question is "how much" extra
> overhead? With the program being SAS (which I think is CPU heavy most of
> the time), the percentage is likely small compared to the total CPU
> usage.
>
I wonder how intelligent the Linux pipe mechanism is? If the connection
works by something equivalent to QSAM's get/locate, put/locate, the overhead
would be miniscule; just passing pointers and reactivating the pipeline
stages?
Leslie
> --
> John McKown (from home)
> Maranatha! <><
>
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