Let's make it easier to pin threads created via a ThreadContext to
all host CPUs currently belonging to a given set of host NUMA nodes --
which is the common case.
"node-affinity" is simply a shortcut for setting "cpu-affinity" manually
to the list of host CPUs belonging to the set of host nodes. This property
can only be written.
A simple QEMU example to set the CPU affinity to host node 1 on a system
with two nodes, 24 CPUs each, whereby odd-numbered host CPUs belong to
host node 1:
qemu-system-x86_64 -S \
-object thread-context,id=tc1,node-affinity=1
And we can query the cpu-affinity via HMP/QMP:
(qemu) qom-get tc1 cpu-affinity
[
1,
3,
5,
7,
9,
11,
13,
15,
17,
19,
21,
23,
25,
27,
29,
31,
33,
35,
37,
39,
41,
43,
45,
47
]
We cannot query the node-affinity:
(qemu) qom-get tc1 node-affinity
Error: Insufficient permission to perform this operation
But note that due to dynamic library loading this example will not work
before we actually make use of thread_context_create_thread() in QEMU
code, because the type will otherwise not get registered. We'll wire
this up next to make it work.
Note that if the host CPUs for a host node change due do CPU hot(un)plug
CPU onlining/offlining (i.e., lscpu output changes) after the ThreadContext
was started, the CPU affinity will not get updated.
Reviewed-by: Michal Privoznik <mpriv...@redhat.com>
Acked-by: Markus Armbruster <arm...@redhat.com>
Signed-off-by: David Hildenbrand <da...@redhat.com>
---
qapi/qom.json | 9 ++++-
util/meson.build | 2 +-
util/thread-context.c | 84 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 93 insertions(+), 2 deletions(-)
diff --git a/qapi/qom.json b/qapi/qom.json
index 8013ba4b82..5a2db663f0 100644
--- a/qapi/qom.json
+++ b/qapi/qom.json
@@ -839,10 +839,17 @@
# threads created in the thread context (default: QEMU main
# thread CPU affinity)
#
+# @node-affinity: the list of host node numbers that will be resolved to a list
+# of host CPU numbers used as CPU affinity. This is a shortcut
+# for specifying the list of host CPU numbers belonging to the
+# host nodes manually by setting @cpu-affinity. (default: QEMU
+# main thread affinity)
