From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752020AbdIFHIt (ORCPT ); Wed, 6 Sep 2017 03:08:49 -0400 Received: from merlin.infradead.org ([205.233.59.134]:60334 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751008AbdIFHIs (ORCPT ); Wed, 6 Sep 2017 03:08:48 -0400 Date: Wed, 6 Sep 2017 09:08:16 +0200 From: Peter Zijlstra To: Waiman Long Cc: Juergen Gross , linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, x86@kernel.org, virtualization@lists.linux-foundation.org, jeremy@goop.org, chrisw@sous-sol.org, akataria@vmware.com, rusty@rustcorp.com.au, boris.ostrovsky@oracle.com, hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com Subject: Re: [PATCH 3/4] paravirt: add virt_spin_lock pvops function Message-ID: <20170906070816.s6rtgtqpljnbudux@hirez.programming.kicks-ass.net> References: <20170905132444.7163-1-jgross@suse.com> <20170905132444.7163-4-jgross@suse.com> <42918500-4487-f0d8-e6fd-99e4d0d7f1bf@suse.com> <3a2eefe7-5c0b-9768-2bb8-03c947133b06@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Guys, please trim email. On Tue, Sep 05, 2017 at 10:31:46AM -0400, Waiman Long wrote: > For clarification, I was actually asking if you consider just adding one > more jump label to skip it for Xen/KVM instead of making > virt_spin_lock() a pv-op. I don't understand. What performance are you worried about. Native will now do: "xor rax,rax; jnz some_cold_label" that's fairly trival code.