Hi,
At 10:50 AM 2/05/2001 +0200, Ingo Molnar wrote:
>i think Zach's phhttpd is an important milestone as well, it's the first
>userspace webserver that shows how to use event-based, sigio-based async
>networking IO and sendfile() under Linux. (I believe it had some
>performance problems related to sigio queue overflow, these issues might
>be solved in the latest kernels.) The zerocopy enhancements should help
>phhttpd as well.
my experience with sigio-based event-handlers is that the net-gain of
event-driven i/o is mitigated by the fact that SIGIO is based on signals.
the problem with signals for this purpose are:
(a) you go thru a syncronization point in the kernel. signals are protected
by a spinlock.
it doesn't scale with SMP.
(b) SI_PAD_SIZE
explicitly, (b) means that you have an awful lot of memory-accesses going
on for every signal.
my experience with the overhead is that it mitigates the advantages when
you become bottlenecked on memory-bus-accesses.
cheers,
lincoln.
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This archive was generated by hypermail 2b29 : Mon May 07 2001 - 21:00:15 EST