Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1398158

Re: [RFC PATCH 0/2] net: threadable napi poll loop

From Eric Dumazet <eric.dumazet@gmail.com>
Newsgroups linux.kernel
Subject Re: [RFC PATCH 0/2] net: threadable napi poll loop
Date 2016-05-10 16:40 +0200
Message-ID <rxgZk-42L-29@gated-at.bofh.it> (permalink)
References <rxgFY-3QP-7@gated-at.bofh.it>
Organization linux.* mail to news gateway

Show all headers | View raw

On Tue, 2016-05-10 at 16:11 +0200, Paolo Abeni wrote:
> Currently, the softirq loop can be scheduled both inside the ksofirqd kernel
> thread and inside any running process. This makes nearly impossible for the
> process scheduler to balance in a fair way the amount of time that
> a given core spends performing the softirq loop.
> 
> Under high network load, the softirq loop can take nearly 100% of a given CPU,
> leaving very little time for use space processing. On single core hosts, this
> means that the user space can nearly starve; for example super_netperf
> UDP_STREAM tests towards a remote single core vCPU guest[1] can measure an
> aggregated throughput of a few thousands pps, and the same behavior can be
> reproduced even on bare-metal, eventually simulating a single core with taskset
> and/or sysfs configuration.

I hate these patches and ideas guys, sorry. That is before my breakfast,
but still...

I have enough hard time dealing with loads where ksoftirqd has to
compete with user threads that thought that playing with priorities was
a nice idea.

Guess what, when they lose networking they complain.

We already have ksoftirqd to normally cope with the case you are
describing.

If it is not working as intended, please identify the bugs and fix them,
instead of adding yet another tests in fast path and extra complexity in
the stack.

In the one vcpu case, allowing the user thread to consume more UDP
packets from the target UDP socket will also make your NIC drop more
packets, that are not necessarily packets for the same socket.

So you are shifting the attack to a different target,
at the expense of more kernel bloat.

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[RFC PATCH 0/2] net: threadable napi poll loop Paolo Abeni <pabeni@redhat.com> - 2016-05-10 16:20 +0200
  [RFC PATCH 2/2] net: add sysfs attribute to control napi threaded mode Paolo Abeni <pabeni@redhat.com> - 2016-05-10 16:20 +0200
  Re: [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet <eric.dumazet@gmail.com> - 2016-05-10 16:40 +0200
    Re: [RFC PATCH 0/2] net: threadable napi poll loop David Miller <davem@davemloft.net> - 2016-05-10 18:00 +0200
    Re: [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet <eric.dumazet@gmail.com> - 2016-05-10 18:10 +0200
      Re: [RFC PATCH 0/2] net: threadable napi poll loop Paolo Abeni <pabeni@redhat.com> - 2016-05-10 22:30 +0200
        Re: [RFC PATCH 0/2] net: threadable napi poll loop David Miller <davem@davemloft.net> - 2016-05-10 22:50 +0200
          Re: [RFC PATCH 0/2] net: threadable napi poll loop David Miller <davem@davemloft.net> - 2016-05-10 23:00 +0200
            Re: [RFC PATCH 0/2] net: threadable napi poll loop Rik van Riel <riel@redhat.com> - 2016-05-10 23:10 +0200
          Re: [RFC PATCH 0/2] net: threadable napi poll loop Rik van Riel <riel@redhat.com> - 2016-05-10 23:00 +0200
    Re: [RFC PATCH 0/2] net: threadable napi poll loop Paolo Abeni <pabeni@redhat.com> - 2016-05-10 18:10 +0200
    Re: [RFC PATCH 0/2] net: threadable napi poll loop Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-05-10 22:50 +0200
      Re: [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet <edumazet@google.com> - 2016-05-10 23:10 +0200
        Re: [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet <eric.dumazet@gmail.com> - 2016-05-10 23:40 +0200
          Re: [RFC PATCH 0/2] net: threadable napi poll loop Rik van Riel <riel@redhat.com> - 2016-05-10 23:40 +0200
            Re: [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet <eric.dumazet@gmail.com> - 2016-05-11 00:00 +0200
              Re: [RFC PATCH 0/2] net: threadable napi poll loop Rik van Riel <riel@redhat.com> - 2016-05-11 00:10 +0200
              Re: [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet <eric.dumazet@gmail.com> - 2016-05-11 00:10 +0200
                Re: [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet <eric.dumazet@gmail.com> - 2016-05-11 00:50 +0200
              Re: [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet <eric.dumazet@gmail.com> - 2016-05-11 20:00 +0200
        Re: [RFC PATCH 0/2] net: threadable napi poll loop Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-05-11 00:40 +0200
          Re: [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet <eric.dumazet@gmail.com> - 2016-05-11 01:00 +0200
            Re: [RFC PATCH 0/2] net: threadable napi poll loop Peter Zijlstra <peterz@infradead.org> - 2016-05-11 09:00 +0200
              Re: [RFC PATCH 0/2] net: threadable napi poll loop Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-05-11 15:20 +0200
                Re: [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet <edumazet@google.com> - 2016-05-11 16:50 +0200
                Re: [RFC PATCH 0/2] net: threadable napi poll loop Rik van Riel <riel@redhat.com> - 2016-05-11 17:10 +0200
                Re: [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet <eric.dumazet@gmail.com> - 2016-05-11 18:00 +0200
              Re: [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet <eric.dumazet@gmail.com> - 2016-05-12 00:00 +0200
            Re: [RFC PATCH 0/2] net: threadable napi poll loop Paolo Abeni <pabeni@redhat.com> - 2016-05-11 11:50 +0200
              Re: [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet <eric.dumazet@gmail.com> - 2016-05-11 15:10 +0200
                Re: [RFC PATCH 0/2] net: threadable napi poll loop Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-05-11 15:40 +0200
                Re: [RFC PATCH 0/2] net: threadable napi poll loop Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-05-11 15:50 +0200
                Re: [RFC PATCH 0/2] net: threadable napi poll loop Paolo Abeni <pabeni@redhat.com> - 2016-05-11 16:40 +0200
                Re: [RFC PATCH 0/2] net: threadable napi poll loop Eric Dumazet <edumazet@google.com> - 2016-05-11 16:50 +0200
                Re: [RFC PATCH 0/2] net: threadable napi poll loop Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-05-12 00:50 +0200
  Re: [RFC PATCH 0/2] net: threadable napi poll loop Thomas Gleixner <tglx@linutronix.de> - 2016-05-10 18:00 +0200
    Re: [RFC PATCH 0/2] net: threadable napi poll loop Paolo Abeni <pabeni@redhat.com> - 2016-05-10 22:50 +0200

csiph-web