From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raghavendra K T Subject: Re: [PATCH RFC v5 4/8] pvqspinlock, x86: Allow unfair spinlock in a real PV environment Date: Tue, 04 Mar 2014 23:20:07 +0530 Message-ID: <5316124F.3050602@linux.vnet.ibm.com> References: <1393427668-60228-1-git-send-email-Waiman.Long@hp.com> <1393427668-60228-5-git-send-email-Waiman.Long@hp.com> <20140226170734.GB20775@phenom.dumpdata.com> <5310C21F.7000809@hp.com> <53145FAD.3020905@redhat.com> <5315EE2E.2060002@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5315EE2E.2060002@hp.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Waiman Long Cc: Jeremy Fitzhardinge , Peter Zijlstra , virtualization@lists.linux-foundation.org, Andi Kleen , "H. Peter Anvin" , Michel Lespinasse , Alok Kataria , linux-arch@vger.kernel.org, x86@kernel.org, Ingo Molnar , Scott J Norton , xen-devel@lists.xenproject.org, "Paul E. McKenney" , Alexander Fyodorov , Rik van Riel , Arnd Bergmann , Konrad Rzeszutek Wilk , Daniel J Blueman , Oleg Nesterov , Steven Rostedt , Chris Wright , George Spelvin , Thomas Gleixner , Aswin Chandramouleeswaran , Chegu List-Id: linux-arch.vger.kernel.org > The PV code in the v5 patch did seem to improve benchmark performance > with moderate to heavy spinlock contention. However, I didn't see much > CPU kicking going on. My theory is that the additional PV code > complicates the pause loop timing so that the hardware PLE didn't kick > in, whereas the original pause loop is pretty simple causing PLE to > happen fairly frequently. you could play with ple_gap parameter to make it work for bigger spin-loops in such cases.