From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Date: Tue, 19 Aug 2008 11:42:29 +0000 Subject: Re: [PATCH 4/4] kvmppc: convert wrteei to wrtee as kvm guest optimization Message-Id: <200808191342.29918.arnd@arndb.de> List-Id: References: <1219142204-12044-1-git-send-email-ehrhardt@linux.vnet.ibm.com> <1219142204-12044-5-git-send-email-ehrhardt@linux.vnet.ibm.com> In-Reply-To: <1219142204-12044-5-git-send-email-ehrhardt@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linuxppc-dev@ozlabs.org Cc: hollisb@us.ibm.com, kvm-ppc@vger.kernel.org On Tuesday 19 August 2008, ehrhardt@linux.vnet.ibm.com wrote: > Dependent on the already existing CONFIG_KVM_GUEST config option this patch > changes wrteei to wrtee allowing the hypervisor to rewrite those to nontrapping > instructions. Maybe we should split the kvm guest otpimizations in two parts > one for the overhead free optimizations and on for the rest that might add > some complexity for non virtualized execution (like this one). > > Signed-off-by: Christian Ehrhardt How significant is the performance impact of this change for non-virtualized systems? If it's very low, maybe you should not bother with the #ifdef, and if it's noticable, you might be better off using dynamic patching for this. Arnd <>< From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from moutng.kundenserver.de (moutng.kundenserver.de [212.227.126.187]) by ozlabs.org (Postfix) with ESMTP id 42FDEDDED0 for ; Tue, 19 Aug 2008 21:44:08 +1000 (EST) From: Arnd Bergmann To: linuxppc-dev@ozlabs.org Subject: Re: [PATCH 4/4] kvmppc: convert wrteei to wrtee as kvm guest optimization Date: Tue, 19 Aug 2008 13:42:29 +0200 References: <1219142204-12044-1-git-send-email-ehrhardt@linux.vnet.ibm.com> <1219142204-12044-5-git-send-email-ehrhardt@linux.vnet.ibm.com> In-Reply-To: <1219142204-12044-5-git-send-email-ehrhardt@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Message-Id: <200808191342.29918.arnd@arndb.de> Cc: hollisb@us.ibm.com, kvm-ppc@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tuesday 19 August 2008, ehrhardt@linux.vnet.ibm.com wrote: > Dependent on the already existing CONFIG_KVM_GUEST config option this patch > changes wrteei to wrtee allowing the hypervisor to rewrite those to nontrapping > instructions. Maybe we should split the kvm guest otpimizations in two parts > one for the overhead free optimizations and on for the rest that might add > some complexity for non virtualized execution (like this one). > > Signed-off-by: Christian Ehrhardt How significant is the performance impact of this change for non-virtualized systems? If it's very low, maybe you should not bother with the #ifdef, and if it's noticable, you might be better off using dynamic patching for this. Arnd <><