From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44445) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZX3MA-0007NJ-NA for qemu-devel@nongnu.org; Wed, 02 Sep 2015 04:25:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZX3M5-0001b1-Qn for qemu-devel@nongnu.org; Wed, 02 Sep 2015 04:25:22 -0400 Received: from mail-pa0-f48.google.com ([209.85.220.48]:33303) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZX3M5-0001an-M1 for qemu-devel@nongnu.org; Wed, 02 Sep 2015 04:25:17 -0400 Received: by pabzr2 with SMTP id zr2so1821939pab.0 for ; Wed, 02 Sep 2015 01:25:17 -0700 (PDT) References: <1441077316-24710-1-git-send-email-david@gibson.dropbear.id.au> From: Alexey Kardashevskiy Message-ID: <55E6B268.10506@ozlabs.ru> Date: Wed, 2 Sep 2015 18:25:12 +1000 MIME-Version: 1.0 In-Reply-To: <1441077316-24710-1-git-send-email-david@gibson.dropbear.id.au> Content-Type: text/plain; charset=koi8-r; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC] spapr: Fix default NUMA node allocation for threads List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson , benh@kernel.crashing.org, ehabkost@redhat.com, agraf@suse.de Cc: qemu-ppc@nongnu.org, qemu-devel@nongnu.org On 09/01/2015 01:15 PM, David Gibson wrote: > At present, if guest numa nodes are requested, but the cpus in each node > are not specified, spapr just uses the default behaviour or assigning each > vcpu round-robin to nodes. > > If smp_threads != 1, that will assign adjacent threads in a core to > different NUMA nodes. As well as being just weird, that's a configuration > that can't be represented in the device tree we give to the guest, which > means the guest and qemu end up with different ideas of the NUMA topology. > > This patch implements mc->cpu_index_to_socket_id in the spapr code to > make sure vcpus get assigned to nodes only at the socket granularity. > > Signed-off-by: David Gibson > --- > hw/ppc/spapr.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > The default NUMA allocation is pretty broken for any normal system, > but this at least fixes it for one more case. This is already in my > spapr-next tree, but if I can get a Reviewed-by or two, it will be > ready for merge to mainline. > > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index bf0c64f..8c2b103 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -1820,6 +1820,13 @@ static void spapr_nmi(NMIState *n, int cpu_index, Error **errp) > } > } > > +static unsigned spapr_cpu_index_to_socket_id(unsigned cpu_index) > +{ > + /* Allocate to NUMA nodes on a "socket" basis (not that concept of > + * socket means much for the paravirtualized PAPR platform) */ > + return cpu_index / smp_threads / smp_cores; This bothers me as "ibm,chip-id" is calculated different in spapr_populate_cpu_dt() and your schema gives different socket numbers for weird cases like -smp 16,sockets=3,cores=4,threads=2 In general, I do not really understand why there is "sockets" parameter in QEMU at all... > +} > + > static void spapr_machine_class_init(ObjectClass *oc, void *data) > { > MachineClass *mc = MACHINE_CLASS(oc); > @@ -1836,6 +1843,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data) > mc->kvm_type = spapr_kvm_type; > mc->has_dynamic_sysbus = true; > mc->pci_allow_0_address = true; > + mc->cpu_index_to_socket_id = spapr_cpu_index_to_socket_id; > > fwc->get_dev_path = spapr_get_fw_dev_path; > nc->nmi_monitor_handler = spapr_nmi; > -- Alexey