Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753302AbbH0Jwb (ORCPT ); Thu, 27 Aug 2015 05:52:31 -0400 Received: from blu004-omc1s4.hotmail.com ([65.55.116.15]:56920 "EHLO BLU004-OMC1S4.hotmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753200AbbH0Jw3 (ORCPT ); Thu, 27 Aug 2015 05:52:29 -0400 X-TMN: [Y7OnjOJOMNxWigei7NBoJnT6h4v/7fyhrkyGNSkyrv8=] X-Originating-Email: [wanpeng.li@hotmail.com] Message-ID: From: Wanpeng Li To: Paolo Bonzini CC: David Matlack , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Wanpeng Li Subject: [PATCH v4 0/3] KVM: Dynamic Halt-Polling Date: Thu, 27 Aug 2015 17:52:16 +0800 X-Mailer: git-send-email 1.9.1 X-OriginalArrivalTime: 27 Aug 2015 09:52:27.0376 (UTC) FILETIME=[14ED1F00:01D0E0AE] MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2577 Lines: 62 v3 -> v4: * bring back grow vcpu->halt_poll_ns when interrupt arrives and shrinks when idle VCPU is detected v2 -> v3: * grow/shrink vcpu->halt_poll_ns by *halt_poll_ns_grow or /halt_poll_ns_shrink * drop the macros and hard coding the numbers in the param definitions * update the comments "5-7 us" * remove halt_poll_ns_max and use halt_poll_ns as the max halt_poll_ns time, vcpu->halt_poll_ns start at zero * drop the wrappers * move the grow/shrink logic before "out:" w/ "if (waited)" v1 -> v2: * change kvm_vcpu_block to read halt_poll_ns from the vcpu instead of the module parameter * use the shrink/grow matrix which is suggested by David * set halt_poll_ns_max to 2ms There is a downside of halt_poll_ns since poll is still happen for idle VCPU which can waste cpu usage. This patchset add the ability to adjust halt_poll_ns dynamically, grows halt_poll_ns if an interrupt arrives and shrinks halt_poll_ns when idle VCPU is detected. There are two new kernel parameters for changing the halt_poll_ns: halt_poll_ns_grow and halt_poll_ns_shrink. Test w/ high cpu overcommit ratio, pin vCPUs, and the halt_poll_ns of halt-poll is the default 500000ns, the max halt_poll_ns of dynamic halt-poll is 2ms. Then watch the %C0 in the dump of Powertop tool. The test method is almost from David. +-----------------+----------------+-------------------+ | | | | | w/o halt-poll | w/ halt-poll | dynamic halt-poll | +-----------------+----------------+-------------------+ | | | | | ~0.9% | ~1.8% | ~1.2% | +-----------------+----------------+-------------------+ The always halt-poll will increase ~0.9% cpu usage for idle vCPUs and the dynamic halt-poll drop it to ~0.3% which means that reduce the 67% overhead introduced by always halt-poll. Wanpeng Li (3): KVM: make halt_poll_ns per-VCPU KVM: dynamic halt_poll_ns adjustment KVM: trace kvm_halt_poll_ns grow/shrink include/linux/kvm_host.h | 1 + include/trace/events/kvm.h | 30 ++++++++++++++++++++++++++++ virt/kvm/kvm_main.c | 50 +++++++++++++++++++++++++++++++++++++++++++--- 3 files changed, 78 insertions(+), 3 deletions(-) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/