From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761007AbbBIQFF (ORCPT ); Mon, 9 Feb 2015 11:05:05 -0500 Received: from shelob.surriel.com ([74.92.59.67]:48003 "EHLO shelob.surriel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933520AbbBIQE6 (ORCPT ); Mon, 9 Feb 2015 11:04:58 -0500 From: riel@redhat.com To: paulmck@linux.vnet.ibm.com Cc: linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will.deacon@arm.com, fweisbec@gmail.com, kvm@vger.kernel.org, mtosatti@redhat.com, borntraeger@de.ibm.com, mingo@kernel.org, oleg@redhat.com, lcapitulino@redhat.com, pbonzini@redhat.com Subject: [PATCH -v3 0/6] rcu,nohz,kvm: use RCU extended quiescent state when running KVM guest Date: Mon, 9 Feb 2015 11:04:38 -0500 Message-Id: <1423497884-21615-1-git-send-email-riel@redhat.com> X-Mailer: git-send-email 1.9.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When running a KVM guest on a system with NOHZ_FULL enabled, and the KVM guest running with idle=poll mode, we still get wakeups of the rcuos/N threads. This problem has already been solved for user space by telling the RCU subsystem that the CPU is in an extended quiescent state while running user space code. This patch series extends that code a little bit to make it usable to track KVM guest space, too. I tested the code by booting a KVM guest with idle=poll, on a system with NOHZ_FULL enabled on most CPUs, and a VCPU thread bound to a CPU. In a 10 second interval, rcuos/N threads on other CPUs got woken up several times, while the rcuos thread on the CPU running the bound and alwasy running VCPU thread never got woken up once. Thanks to Christian Borntraeger and Paul McKenney for reviewing the first version of this patch series, and helping optimize patch 4/5. Thanks to Frederic Weisbecker for further enhancements. Apologies to Catalin and Will for not fixing up ARM. I am not familiar with ARM assembly, and not sure how to pass a constant argument to a function from assembly code on ARM :)