Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932883AbbHXMxt (ORCPT ); Mon, 24 Aug 2015 08:53:49 -0400 Received: from blu004-omc1s15.hotmail.com ([65.55.116.26]:61374 "EHLO BLU004-OMC1S15.hotmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932718AbbHXMxq (ORCPT ); Mon, 24 Aug 2015 08:53:46 -0400 X-TMN: [vjvcCQOXBk3/BklNkuCMu3EQ4ioE/SzsCDO67ffQ0tU=] X-Originating-Email: [wanpeng.li@hotmail.com] Message-ID: From: Wanpeng Li To: Paolo Bonzini CC: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Wanpeng Li Subject: [PATCH 2/3] KVM: dynamise halt_poll_ns adjustment Date: Mon, 24 Aug 2015 20:53:23 +0800 X-Mailer: git-send-email 1.9.1 In-Reply-To: <1440420804-15198-1-git-send-email-wanpeng.li@hotmail.com> References: <1440420804-15198-1-git-send-email-wanpeng.li@hotmail.com> X-OriginalArrivalTime: 24 Aug 2015 12:53:44.0350 (UTC) FILETIME=[E8DE63E0:01D0DE6B] 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: 4501 Lines: 150 There are two new kernel parameters for changing the halt_poll_ns: halt_poll_ns_grow and halt_poll_ns_shrink. halt_poll_ns_grow affects halt_poll_ns when an interrupt arrives and halt_poll_ns_shrink does it when idle VCPU is detected. halt_poll_ns_shrink/ | halt_poll_ns_grow | interrupt arrives | idle VCPU is detected ---------------------+----------------------+------------------- < 1 | = halt_poll_ns | = 0 < halt_poll_ns | *= halt_poll_ns_grow | /= halt_poll_ns_shrink otherwise | += halt_poll_ns_grow | -= halt_poll_ns_shrink A third new parameter, halt_poll_ns_max, controls the maximal halt_poll_ns; it is internally rounded down to a closest multiple of halt_poll_ns_grow. Signed-off-by: Wanpeng Li --- virt/kvm/kvm_main.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 80 insertions(+), 1 deletion(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index a122b52..bcfbd35 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -66,9 +66,28 @@ MODULE_AUTHOR("Qumranet"); MODULE_LICENSE("GPL"); -static unsigned int halt_poll_ns; +#define KVM_HALT_POLL_NS 500000 +#define KVM_HALT_POLL_NS_GROW 2 +#define KVM_HALT_POLL_NS_SHRINK 0 +#define KVM_HALT_POLL_NS_MAX \ + INT_MAX / KVM_HALT_POLL_NS_GROW + +static unsigned int halt_poll_ns = KVM_HALT_POLL_NS; module_param(halt_poll_ns, uint, S_IRUGO | S_IWUSR); +/* Default doubles per-vcpu halt_poll_ns. */ +static int halt_poll_ns_grow = KVM_HALT_POLL_NS_GROW; +module_param(halt_poll_ns_grow, int, S_IRUGO); + +/* Default resets per-vcpu halt_poll_ns . */ +int halt_poll_ns_shrink = KVM_HALT_POLL_NS_SHRINK; +module_param(halt_poll_ns_shrink, int, S_IRUGO); + +/* Default is to compute the maximum so we can never overflow. */ +unsigned int halt_poll_ns_actual_max = KVM_HALT_POLL_NS_MAX; +unsigned int halt_poll_ns_max = KVM_HALT_POLL_NS_MAX; +module_param(halt_poll_ns_max, int, S_IRUGO); + /* * Ordering of locks: * @@ -1907,6 +1926,62 @@ void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn) } EXPORT_SYMBOL_GPL(kvm_vcpu_mark_page_dirty); +static unsigned int __grow_halt_poll_ns(unsigned int val) +{ + if (halt_poll_ns_grow < 1) + return halt_poll_ns; + + val = min(val, halt_poll_ns_actual_max); + + if (val == 0) + return halt_poll_ns; + + if (halt_poll_ns_grow < halt_poll_ns) + val *= halt_poll_ns_grow; + else + val += halt_poll_ns_grow; + + return val; +} + +static unsigned int __shrink_halt_poll_ns(int val, int modifier, int minimum) +{ + if (modifier < 1) + return 0; + + if (modifier < halt_poll_ns) + val /= modifier; + else + val -= modifier; + + return val; +} + +static void grow_halt_poll_ns(struct kvm_vcpu *vcpu) +{ + vcpu->halt_poll_ns = __grow_halt_poll_ns(vcpu->halt_poll_ns); +} + +static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu) +{ + vcpu->halt_poll_ns = __shrink_halt_poll_ns(vcpu->halt_poll_ns, + halt_poll_ns_shrink, halt_poll_ns); +} + +/* + * halt_poll_ns_actual_max is computed to be one grow_halt_poll_ns() below + * halt_poll_ns_max. (See __grow_halt_poll_ns for the reason.) + * This prevents overflows, because ple_halt_poll_ns is int. + * halt_poll_ns_max effectively rounded down to a multiple of halt_poll_ns_grow in + * this process. + */ +static void update_halt_poll_ns_actual_max(void) +{ + halt_poll_ns_actual_max = + __shrink_halt_poll_ns(max(halt_poll_ns_max, halt_poll_ns), + halt_poll_ns_grow, INT_MIN); +} + static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu) { if (kvm_arch_vcpu_runnable(vcpu)) { @@ -1941,6 +2016,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) */ if (kvm_vcpu_check_block(vcpu) < 0) { ++vcpu->stat.halt_successful_poll; + grow_halt_poll_ns(vcpu); goto out; } cur = ktime_get(); @@ -1954,6 +2030,8 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) break; waited = true; + if (halt_poll_ns) + shrink_halt_poll_ns(vcpu); schedule(); } @@ -2950,6 +3028,7 @@ static void hardware_enable_nolock(void *junk) cpumask_set_cpu(cpu, cpus_hardware_enabled); r = kvm_arch_hardware_enable(); + update_halt_poll_ns_actual_max(); if (r) { cpumask_clear_cpu(cpu, cpus_hardware_enabled); -- 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/