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[204.195.22.127]) by smtp.gmail.com with ESMTPSA id v1sm452386pgl.11.2020.05.19.17.06.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 May 2020 17:06:45 -0700 (PDT) Date: Tue, 19 May 2020 17:06:37 -0700 From: Stephen Hemminger To: Thomas Gleixner Cc: "Ahmed S. Darwish" , Peter Zijlstra , Ingo Molnar , Will Deacon , "Paul E. McKenney" , "Sebastian A. Siewior" , Steven Rostedt , LKML , "David S. Miller" , Jakub Kicinski , netdev@vger.kernel.org Subject: Re: [PATCH v1 01/25] net: core: device_rename: Use rwsem instead of a seqcount Message-ID: <20200519170637.56d1a20a@hermes.lan> In-Reply-To: <87lfln5w61.fsf@nanos.tec.linutronix.de> References: <20200519214547.352050-1-a.darwish@linutronix.de> <20200519214547.352050-2-a.darwish@linutronix.de> <20200519150159.4d91af93@hermes.lan> <87v9kr5zt7.fsf@nanos.tec.linutronix.de> <20200519161141.5fbab730@hermes.lan> <87lfln5w61.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, 20 May 2020 01:42:30 +0200 Thomas Gleixner wrote: > Stephen Hemminger writes: > > On Wed, 20 May 2020 00:23:48 +0200 > > Thomas Gleixner wrote: > >> No. We did not. -ENOTESTCASE > > > > Please try, it isn't that hard.. > > > > # time for ((i=0;i<1000;i++)); do ip li add dev dummy$i type dummy; done > > > > real 0m17.002s > > user 0m1.064s > > sys 0m0.375s > > And that solves the incorrectness of the current code in which way? Agree that the current code is has evolved over time to a state where it is not correct in the case of Preempt-RT. The motivation for the changes to seqcount goes back many years when there were ISP's that were concerned about scaling of tunnels, vlans etc. Is it too much to ask for a simple before/after test of your patch as part of the submission. You probably measure latency changes to the nanosecond. Getting it correct without causing user complaints.