From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [net-next PATCH v2 5/8] net: Track start of busy loop instead of when it should end Date: Thu, 23 Mar 2017 18:24:42 -0700 Message-ID: <1490318682.9687.22.camel@edumazet-glaptop3.roam.corp.google.com> References: <20170323211820.12615.88907.stgit@localhost.localdomain> <20170323213742.12615.85793.stgit@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20170323213742.12615.85793.stgit@localhost.localdomain> Sender: linux-kernel-owner@vger.kernel.org To: Alexander Duyck 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 List-Id: linux-api@vger.kernel.org On Thu, 2017-03-23 at 14:37 -0700, Alexander Duyck wrote: > From: Alexander Duyck > > 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.