From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH v11 14/16] pvqspinlock: Add qspinlock para-virtualization support Date: Sun, 15 Jun 2014 15:16:54 +0200 Message-ID: <20140615131654.GJ11371@laptop.programming.kicks-ass.net> References: <1401464642-33890-1-git-send-email-Waiman.Long@hp.com> <1401464642-33890-15-git-send-email-Waiman.Long@hp.com> <20140612081731.GM3213@twins.programming.kicks-ass.net> <539A1229.1050309@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <539A1229.1050309@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: linux-arch@vger.kernel.org, Rik van Riel , Raghavendra K T , Oleg Nesterov , Gleb Natapov , kvm@vger.kernel.org, Konrad Rzeszutek Wilk , Scott J Norton , x86@kernel.org, Paolo Bonzini , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Ingo Molnar , Chegu Vinod , David Vrabel , "H. Peter Anvin" , xen-devel@lists.xenproject.org, Thomas Gleixner , "Paul E. McKenney" , Linus Torvalds , Boris Ostrovsky List-Id: virtualization@lists.linuxfoundation.org On Thu, Jun 12, 2014 at 04:48:41PM -0400, Waiman Long wrote: > I don't have a good understanding of the kernel alternatives mechanism. I didn't either; I do now, cost me a whole day reading up on alternative/paravirt code patching. See the patches I just send out; I got the 'native' case with paravirt enabled to be one NOP worse than the native case without paravirt -- for queue_spin_unlock. The lock slowpath is several nops and some pointless movs more expensive.