This patch changes the way data to fill the nodeinfo structure are
gathered. We've gathere the test data by iterating processors an sockets
separately from nodes. The reported data was based solely on information
about core id. Problems arise when eg cores in mulit-processor machines
don't have same id's on both processors or maybe one physical processor
contains more NUMA nodes.
This patch changes the approach how we detect processors and nodes. Now
we start at enumerating nodes and for each node processors, sockets and
threads are enumerated separately. This approach provides acurate data
that comply to docs about the nodeinfo structure. This also enables to
get rid of hacks: see commits 10d9038b74,
ac9dd4a676. (Those changes in nodeinfo.c
are efectively reverted by this patch).
This patch also changes output of one of the tests, as the processor
topology is now acquired more precisely.
Make it obvious why we need Osier's patch in commit 10d9038b
to fix NUMA parsing of an AMD machine with two cores sharing
a socket id.
* tests/nodeinfotest.c (linuxTestCompareFiles): Enhance the test.
* tests/nodeinfodata/linux-nodeinfo-sysfs-test-*-output.txt: Update.
"Instead of developing one CPU with 12 cores, the Magny Cours is
actually two 6 core “Bulldozer” CPUs combined in to one package"
I.e, each package has two NUMA nodes, and the two numa nodes share
the same core ID set (0-6), which means parsing the cores number
from sysfs doesn't work in this case.
And the wrong CPU number could cause three problems for libvirt:
1) performance lost
A domain without "cpuset" or "placement='auto'" (to drive numad)
specified will be only pinned to part of the CPUs.
2) domain can be started
If a domain uses numad, and the advisory nodeset returned from
numad contains node which exceeds the range of wrong total CPU
number. The domain will fail to start, as the bitmask passed to
sched_setaffinity could be fully filled with zero.
3) wrong CPU number affects lots of stuffs.
E.g. for command "virsh vcpuinfo", "virsh vcpupin", it will always
output with the truncated CPU list.
For more details:
https://www.redhat.com/archives/libvir-list/2012-May/msg00607.html
This patch is to fix the problem by parsing /proc/cpuinfo to get
the value of field "cpu cores", and use it as nodeinfo->cores if
it's greater than the cores number from sysfs.
Test 2 data grabbed from a 2-core 1-node laptop.
Test 3 data grabbed from a 48-cpu AMD Magny Cours box.
* tests/nodeinfodata/linux-nodeinfo-sysfs-test-2*: New test data.
* tests/nodeinfodata/linux-nodeinfo-sysfs-test-3*: Likewise.
* tests/nodeinfotest.c (mymain): Run them.
* cfg.mk
(exclude_file_name_regexp--sc_prohibit_empty_lines_at_EOF): Exempt
new test files.
