From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3rqrNP17XhzDqxj for ; Thu, 14 Jul 2016 19:43:01 +1000 (AEST) Subject: Re: [PATCH V2 4/5] kvm/stats: Add provisioning for 64-bit vcpu statistics To: Christian Borntraeger , David Matlack References: <1468220912-22828-1-git-send-email-sjitindarsingh@gmail.com> <1468220912-22828-4-git-send-email-sjitindarsingh@gmail.com> <9253603f-fbfb-09f1-9576-9291d1587397@redhat.com> <353f05d6-74a2-69c0-978d-7c3df6b33755@redhat.com> <578681D6.8070801@de.ibm.com> Cc: Suraj Jitindar Singh , linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, mpe@ellerman.id.au, paulus@samba.org, benh@kernel.crashing.org, kvm list , agraf@suse.com, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= From: Paolo Bonzini Message-ID: <46eaef93-af3a-4dbb-eb3e-df3d63b1eb1c@redhat.com> Date: Thu, 14 Jul 2016 11:42:50 +0200 MIME-Version: 1.0 In-Reply-To: <578681D6.8070801@de.ibm.com> Content-Type: text/plain; charset=utf-8 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 13/07/2016 20:00, Christian Borntraeger wrote: >>> >> I thought u64 still existed on 32-bit architectures. unsigned long >>> >> would be fine but with the caveat that certain stats would overflow on >>> >> 32-bit architectures. >> > >> > Yes, but not all 32-bit architectures can do atomic read-modify-write >> > (e.g. add) operations on 64-bit values. > So what about only doing it for the VCPU events? Those should be only > modified by one CPU. We would have some odd values on 32bit overflow, but > this will be certainly better than just start with 0 If that's good enough for PPC, that's fine. Paolo