From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-x244.google.com (mail-pa0-x244.google.com [IPv6:2607:f8b0:400e:c03::244]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3sw8HX1vhWzDt2f for ; Fri, 14 Oct 2016 11:54:00 +1100 (AEDT) Received: by mail-pa0-x244.google.com with SMTP id fn2so4490752pad.1 for ; Thu, 13 Oct 2016 17:54:00 -0700 (PDT) From: Suraj Jitindar Singh To: pbonzini@redhat.com, rkrcmar@redhat.com, agraf@suse.com, corbet@lwn.net Cc: paulus@samba.org, mpe@ellerman.id.au, sam.bobroff@au1.ibm.com, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, benh@kernel.crashing.org, linux-doc@vger.kernel.org, Suraj Jitindar Singh Subject: [PATCH 4/6] powerpc/kvm: Decrease the powerpc default halt poll max value Date: Fri, 14 Oct 2016 11:53:22 +1100 Message-Id: <1476406404-32752-5-git-send-email-sjitindarsingh@gmail.com> In-Reply-To: <1476406404-32752-1-git-send-email-sjitindarsingh@gmail.com> References: <1476406404-32752-1-git-send-email-sjitindarsingh@gmail.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , KVM_HALT_POLL_NS_DEFAULT is an arch specific constant which sets the default value of the halt_poll_ns kvm module parameter which determines the global maximum halt polling interval. The current value for powerpc is 500000 (500us) which means that any repetitive workload with a period of less than that can drive the cpu usage to 100% where it may have been mostly idle without halt polling. This presents the possibility of a large increase in power usage with a comparatively small performance benefit. Reduce the default to 10000 (10us) and a user can tune this themselves to set their affinity for halt polling based on the trade off between power and performance which they are willing to make. Signed-off-by: Suraj Jitindar Singh --- arch/powerpc/include/asm/kvm_host.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index 28350a2..037b6a1 100644 --- a/arch/powerpc/include/asm/kvm_host.h +++ b/arch/powerpc/include/asm/kvm_host.h @@ -48,7 +48,7 @@ #ifdef CONFIG_KVM_MMIO #define KVM_COALESCED_MMIO_PAGE_OFFSET 1 #endif -#define KVM_HALT_POLL_NS_DEFAULT 500000 +#define KVM_HALT_POLL_NS_DEFAULT 10000 /* 10 us */ /* These values are internal and can be increased later */ #define KVM_NR_IRQCHIPS 1 -- 2.5.5