[PATCH] qemuBuildThreadContextProps: Generate ThreadContext less frequently

[Ján Tomko]

On a Thursday in 2023, Michal Privoznik wrote:
>Currently, the ThreadContext object is generated whenever we see
>.host-nodes attribute for a memory-backend-* object. The idea was
>that when the backend is pinned to a specific set of host NUMA
>nodes, then the allocation could be happening on CPUs from those
>nodes too. But this may not be always possible.
>
>Users might configure their guests in such way that vCPUs and
>corresponding guest NUMA nodes are on different host NUMA nodes
>than emulator thread. In this case, ThreadContext won't work,
>because ThreadContext objects live in context of the emulator
>thread (vCPU threads are moved around by us later, when emulator
>thread finished its setup and spawned vCPU threads - see
>qemuProcessSetupVcpus()). Therefore, memory allocation is done by
>emulator thread which is pinned to a subset of host NUMA nodes,
>but tries to create a ThreadContext object with a disjoint subset
>of host NUMA nodes, which fails.
>
>Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2154750
>Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>---
> src/qemu/qemu_command.c                               | 11 ++++++-----
> .../hugepages-memaccess2.x86_64-latest.args           |  9 +++------
> .../memory-hotplug-virtio-mem.x86_64-latest.args      |  3 +--
> .../numatune-memnode.x86_64-latest.args               |  9 +++------
> .../numatune-system-memory.x86_64-latest.args         |  3 +--
> 5 files changed, 14 insertions(+), 21 deletions(-)
>

Reviewed-by: Ján Tomko <jtomko at redhat.com>

Jano
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