Re: [RFC PATCH 00/30] Kernel NET policy

From	Andi Kleen <andi@firstfloor.org>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH 00/30] Kernel NET policy
Date	2016-07-18 21:50 +0200
Message-ID	<rWmI9-233-5@gated-at.bofh.it> (permalink)
References	<rWhIu-7l8-7@gated-at.bofh.it> <rWiuR-7Ug-13@gated-at.bofh.it> <rWiXU-85S-15@gated-at.bofh.it> <rWm5r-1OZ-15@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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> I wonder if this can be attacked from a different angle. What would be
> missing to add support for this in user space? The first possibility
> that came to my mind is to just multiplex those hints in the kernel.

"just" is the handwaving part here -- you're proposing a micro kernel
approach where part of the multiplexing job that the kernel is doing
is farmed out to a message passing user space component.

I suspect this would be far more complicated to get right and
perform well than a straight forward monolithic kernel subsystem --
which is traditionally how Linux has approached things.

The daemon would always need to work with out of date state
compared to the latest, because it cannot do any locking with the
kernel state.  So you end up with a complex distributed system with multiple
agents "fighting" with each other, and the tuning agent
never being able to keep up with the actual work.

Also of course it would be fundamentally less efficient than
kernel code doing that, just because of the additional context
switches needed.

-Andi

Thread

[RFC PATCH 00/30] Kernel NET policy kan.liang@intel.com - 2016-07-18 16:30 +0200
  [RFC PATCH 10/30] net/netpolicy: introduce netpolicy object kan.liang@intel.com - 2016-07-18 16:30 +0200
  [RFC PATCH 20/30] net/netpolicy: introduce per socket netpolicy kan.liang@intel.com - 2016-07-18 16:30 +0200
  [RFC PATCH 28/30] net/netpolicy: optimize for queue pair kan.liang@intel.com - 2016-07-18 16:30 +0200
  [RFC PATCH 29/30] net/netpolicy: limit the total record number kan.liang@intel.com - 2016-07-18 16:30 +0200
  [RFC PATCH 30/30] Documentation/networking: Document net policy kan.liang@intel.com - 2016-07-18 16:30 +0200
    Re: [RFC PATCH 30/30] Documentation/networking: Document net policy Randy Dunlap <rdunlap@infradead.org> - 2016-07-18 19:10 +0200
  [RFC PATCH 24/30] net/netpolicy: set rx queues according to policy kan.liang@intel.com - 2016-07-18 16:30 +0200
  [RFC PATCH 23/30] i40e/ethtool: support RX_CLS_LOC_ANY kan.liang@intel.com - 2016-07-18 16:30 +0200
    Re: [RFC PATCH 23/30] i40e/ethtool: support RX_CLS_LOC_ANY Alexander Duyck <alexander.duyck@gmail.com> - 2016-07-18 18:30 +0200
  [RFC PATCH 14/30] net/netpolicy: add MIX policy kan.liang@intel.com - 2016-07-18 16:30 +0200
  [RFC PATCH 19/30] net/netpolicy: implement netpolicy register kan.liang@intel.com - 2016-07-18 16:30 +0200
  [RFC PATCH 27/30] net/netpolicy: fast path for finding the queues kan.liang@intel.com - 2016-07-18 16:30 +0200
  [RFC PATCH 09/30] net/netpolicy: enable and disable net policy kan.liang@intel.com - 2016-07-18 16:40 +0200
  [RFC PATCH 18/30] net/netpolicy: handle channel changes kan.liang@intel.com - 2016-07-18 16:40 +0200
  [RFC PATCH 08/30] net/netpolicy: set and remove irq affinity kan.liang@intel.com - 2016-07-18 16:40 +0200
  [RFC PATCH 16/30] net/netpolicy: net device hotplug kan.liang@intel.com - 2016-07-18 16:40 +0200
  [RFC PATCH 04/30] net/netpolicy: get driver information kan.liang@intel.com - 2016-07-18 16:40 +0200
  [RFC PATCH 15/30] i40e/netpolicy: add MIX policy support kan.liang@intel.com - 2016-07-18 16:40 +0200
  [RFC PATCH 05/30] i40e/netpolicy: implement ndo_get_irq_info kan.liang@intel.com - 2016-07-18 16:40 +0200
  [RFC PATCH 11/30] net/netpolicy: set net policy by policy name kan.liang@intel.com - 2016-07-18 16:40 +0200
  [RFC PATCH 01/30] net: introduce NET policy kan.liang@intel.com - 2016-07-18 16:40 +0200
  [RFC PATCH 03/30] i40e/netpolicy: Implement ndo_netpolicy_init kan.liang@intel.com - 2016-07-18 16:40 +0200
  [RFC PATCH 17/30] net/netpolicy: support CPU hotplug kan.liang@intel.com - 2016-07-18 16:40 +0200
  [RFC PATCH 02/30] net/netpolicy: init NET policy kan.liang@intel.com - 2016-07-18 16:40 +0200
  [RFC PATCH 06/30] net/netpolicy: get CPU information kan.liang@intel.com - 2016-07-18 16:40 +0200
  [RFC PATCH 07/30] net/netpolicy: create CPU and queue mapping kan.liang@intel.com - 2016-07-18 16:40 +0200
  Re: [RFC PATCH 00/30] Kernel NET policy Florian Westphal <fw@strlen.de> - 2016-07-18 17:20 +0200
    Re: [RFC PATCH 00/30] Kernel NET policy Andi Kleen <andi@firstfloor.org> - 2016-07-18 17:50 +0200
      Re: [RFC PATCH 00/30] Kernel NET policy Cong Wang <xiyou.wangcong@gmail.com> - 2016-07-18 20:00 +0200
        Re: [RFC PATCH 00/30] Kernel NET policy Cong Wang <xiyou.wangcong@gmail.com> - 2016-07-18 22:20 +0200
          RE: [RFC PATCH 00/30] Kernel NET policy "Liang, Kan" <kan.liang@intel.com> - 2016-07-18 22:30 +0200
        RE: [RFC PATCH 00/30] Kernel NET policy "Liang, Kan" <kan.liang@intel.com> - 2016-07-18 22:20 +0200
      Re: [RFC PATCH 00/30] Kernel NET policy Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-07-18 21:10 +0200
        Re: [RFC PATCH 00/30] Kernel NET policy Andi Kleen <andi@firstfloor.org> - 2016-07-18 21:50 +0200
          Re: [RFC PATCH 00/30] Kernel NET policy Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-07-19 00:00 +0200
            RE: [RFC PATCH 00/30] Kernel NET policy "Liang, Kan" <kan.liang@intel.com> - 2016-07-19 03:50 +0200
              Re: [RFC PATCH 00/30] Kernel NET policy David Miller <davem@davemloft.net> - 2016-07-19 07:10 +0200
                RE: [RFC PATCH 00/30] Kernel NET policy "Liang, Kan" <kan.liang@intel.com> - 2016-07-19 15:50 +0200
    RE: [RFC PATCH 00/30] Kernel NET policy "Liang, Kan" <kan.liang@intel.com> - 2016-07-18 18:00 +0200
      Re: [RFC PATCH 00/30] Kernel NET policy Florian Westphal <fw@strlen.de> - 2016-07-18 18:20 +0200
        RE: [RFC PATCH 00/30] Kernel NET policy "Liang, Kan" <kan.liang@intel.com> - 2016-07-18 19:50 +0200
      Re: [RFC PATCH 00/30] Kernel NET policy Tom Herbert <tom@herbertland.com> - 2016-07-18 18:40 +0200
        RE: [RFC PATCH 00/30] Kernel NET policy "Liang, Kan" <kan.liang@intel.com> - 2016-07-18 20:00 +0200
  Re: [RFC PATCH 00/30] Kernel NET policy Daniel Borkmann <daniel@iogearbox.net> - 2016-07-18 18:30 +0200
    RE: [RFC PATCH 00/30] Kernel NET policy "Liang, Kan" <kan.liang@intel.com> - 2016-07-18 20:40 +0200
      Re: [RFC PATCH 00/30] Kernel NET policy Daniel Borkmann <daniel@iogearbox.net> - 2016-07-18 23:00 +0200
  Re: [RFC PATCH 00/30] Kernel NET policy Alexander Duyck <alexander.duyck@gmail.com> - 2016-07-18 19:10 +0200
    RE: [RFC PATCH 00/30] Kernel NET policy "Liang, Kan" <kan.liang@intel.com> - 2016-07-18 21:50 +0200
      Re: [RFC PATCH 00/30] Kernel NET policy Andi Kleen <andi@firstfloor.org> - 2016-07-18 22:00 +0200

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