Messages in this thread |  | | Date | Thu, 03 May 2001 09:19:53 +1000 | From | Lincoln Dale <> | Subject | Re: X15 alpha release: as fast as TUX but in user space |
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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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