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Performance issues due to the microkernel/multi-server system architecture?

IRC, freenode, #hurd, 2011-07-26

    < CTKArcher> I read that, because of its microkernel+servers design, the
      hurd was slower than a monolithic kernel, is that confirmed ?
    < youpi> the hurd is currently slower than current monolithic kernels, but
      it's not due to the microkernel + servers design
    < youpi> the microkernel+servers design makes the system call path longer
    < youpi> but you're bound by disk and network speed
    < youpi> so the extra overhead will not hurt so much
    < youpi> except dumb applications keeping doing system calls all the time
      of course, but they are usually considered bogus
    < braunr> there may be some patterns (like applications using pipes
      extensively, e.g. git-svn) which may suffer from the design, but still in
      an acceptable range
    < CTKArcher> so, you are saying that disk and network are more slowing the
      system than the longer system call path and because of that, it wont
      really matter ?
    < youpi> braunr: they should sitll be fixed because they'll suffer (even if
      less) on monolithic kernels
    < youpi> CTKArcher: yes
    < braunr> yes
    < CTKArcher> mmh
    < youpi> CTKArcher: you might want to listen to AST's talk at fosdem 10
      iirc, about minix
    < youpi> they even go as far as using an IPC for each low-level in/out
    < youpi> for security
    < braunr> this has been expected for a long time
    < braunr> which is what motivated research in microkernels
    < CTKArcher> I've already downloaded the video :)
    < youpi> and it has been more and more true with faster and faster cpus
    < braunr> but in 95, processors weren't that fast compared to other
      components as they are now
    < youpi> while disk/mem haven't evovled so fast