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Re: [net-next PATCH v2 5/8] net: Track start of busy loop instead of when it should end

From Eric Dumazet <eric.dumazet@gmail.com>
Newsgroups linux.kernel
Subject Re: [net-next PATCH v2 5/8] net: Track start of busy loop instead of when it should end
Date 2017-03-24 02:30 +0100
Message-ID <tomdb-2rZ-3@gated-at.bofh.it> (permalink)
References <toiCB-8g8-3@gated-at.bofh.it> <toiCC-8g8-19@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Thu, 2017-03-23 at 14:37 -0700, Alexander Duyck wrote:
> From: Alexander Duyck <alexander.h.duyck@intel.com>
> 

> The last bit I changed is to move from using a shift by 10 to just using
> NSEC_PER_USEC and using multiplication for any run time calculations and
> division for a few compile time ones.  This should be more accurate and
> perform about the same on most architectures since modern CPUs typically
> handle multiplication without too much overhead.


busy polling thread can be preempted for more than 2 seconds.

Using usec instead of nanoseconds gave us 3 orders of magnitude cushion.

We do not need nsec accuracy for busy polling users, if this restricts
range and usability under stress.

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Thread

[net-next PATCH v2 5/8] net: Track start of busy loop instead of  when it should end Alexander Duyck <alexander.duyck@gmail.com> - 2017-03-23 22:40 +0100
  Re: [net-next PATCH v2 5/8] net: Track start of busy loop instead  of when it should end Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-24 02:30 +0100
    Re: [net-next PATCH v2 5/8] net: Track start of busy loop instead of  when it should end Alexander Duyck <alexander.duyck@gmail.com> - 2017-03-24 04:50 +0100
      Re: [net-next PATCH v2 5/8] net: Track start of busy loop instead  of when it should end Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-24 05:30 +0100
        Re: [net-next PATCH v2 5/8] net: Track start of busy loop instead  of when it should end Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-24 05:40 +0100
        Re: [net-next PATCH v2 5/8] net: Track start of busy loop instead of  when it should end Alexander Duyck <alexander.duyck@gmail.com> - 2017-03-24 07:00 +0100
          Re: [net-next PATCH v2 5/8] net: Track start of busy loop instead  of when it should end Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-24 12:20 +0100
            Re: [net-next PATCH v2 5/8] net: Track start of busy loop instead of  when it should end Alexander Duyck <alexander.duyck@gmail.com> - 2017-03-24 16:50 +0100

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