Message-ID: <1490318682.9687.22.camel@edumazet-glaptop3.roam.corp.google.com>
Subject: 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>
To: Alexander Duyck <alexander.duyck@gmail.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        sridhar.samudrala@intel.com, edumazet@google.com, davem@davemloft.net,
        linux-api@vger.kernel.org
Date: Thu, 23 Mar 2017 18:24:42 -0700
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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.