Re: Max tcp connections

Dan Kegel (dank@alumni.caltech.edu)
Thu, 11 Nov 1999 23:47:35 -0800


David Schwartz wrote:
> > Signal based I/O is definitely the right approach for scaling
>
> I still find this very hard to believe. How can one fast pass through poll
> (assuming a smarter implementation) be less efficient than the OS sending me
> 5,000 signals? That strikes me as an incredible claim.

Easy. The kernel doesn't send you 5,000 signals. If the
signal queue starts overflowing, it gives up and sends you
a single SIGIO, and you call poll().

The signal model gives you the best of both worlds: low overhead
when only a few fd's at a time need attention (no linear scan),
and low overhead when they all do (same as old poll() method,
but with the extra overhead of a single SIGIO).

sct must be sleeping, or he would have answered like this, I think :-)
- Dan

-- 
(The above is just my personal opinion; I don't speak for my employer,
 except on the occasional talk show.)

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