Re: [libvirt] [PATCHv2 3/3] virsh: Use virNodeGetCPUMap if possible
On 10/31/2012 08:58 PM, Hu Tao wrote:
On Wed, Oct 31, 2012 at 06:20:58PM +0100, Viktor Mihajlovski wrote:
> Modified the places where virNodeGetInfo was used for the purpose
> of obtaining the maximum node CPU number. Transparently falling
> back to virNodeGetInfo in case of failure.
> Wrote utility function vshNodeGetCPUCount to compute node CPU
> number.
>
> +static int
> +vshNodeGetCPUCount(virConnectPtr conn)
> +{
> + int ret;
> + virNodeInfo nodeinfo;
> +
> + if ((ret = virNodeGetCPUMap(conn, NULL, NULL, 0)) < 0) {
> + /* fall back to nodeinfo */
> + if (virNodeGetInfo(conn, &nodeinfo) == 0) {
> + ret = VIR_NODEINFO_MAXCPUS(nodeinfo);
> + }
Isn't VIR_NODEINFO_MAXCPUS buggy? Either don't fall back to nodeinfo
or fix it.
Hmm, and I just realized another issue - on the RHEL 5 box I tested,
there is no /sys/devices/system/cpu/possible, so virNodeGetCPUCount()
currently fails, even though virNodeGetInfo() succeeded. I'm going to
hold off pushing this series until after 1.0.0, to avoid any chance of a
last-minute unintentional regression.
You were asking about VIR_NODEINFO_MAXCPUS:
#define VIR_NODEINFO_MAXCPUS(nodeinfo)
((nodeinfo).nodes*(nodeinfo).sockets*(nodeinfo).cores*(nodeinfo).threads)
I can confirm that virNodeGetInfo misbehaves if enough trailing cpus are
offline, and therefore agree that we need to fix that API:
# virsh nodeinfo
CPU model: x86_64
CPU(s): 2
CPU frequency: 2801 MHz
CPU socket(s): 1
Core(s) per socket: 2
Thread(s) per core: 1
NUMA cell(s): 1
Memory size: 3941792 KiB
# echo 0 > /sys/devices/system/cpu/cpu1/online
# virsh nodeinfo
CPU model: x86_64
CPU(s): 1
CPU frequency: 2801 MHz
CPU socket(s): 1
Core(s) per socket: 1
Thread(s) per core: 1
NUMA cell(s): 1
Memory size: 3941792 KiB
That just changed things from 2 to 1. No fun.
--
Eric Blake eblake(a)redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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