On Thu, Jan 31, 2019 at 10:34:17AM +0100, Michal Privoznik wrote:
https://bugzilla.redhat.com/show_bug.cgi?id=1503284
The way we currently start qemu from CPU affinity POV is as
follows:
1) the child process is set affinity to all online CPUs (unless
some vcpu pinning was given in the domain XML)
2) Once qemu is running, cpuset cgroup is configured taking
memory pinning into account
Problem is that we let qemu allocate its memory just anywhere in
1) and then rely in 2) to be able to move the memory to
configured NUMA nodes. This might not be always possible (e.g.
qemu might lock some parts of its memory) and is very suboptimal
(copying large memory between NUMA nodes takes significant amount
of time).
The solution is to set affinity to one of (in priority order):
- The CPUs associated with NUMA memory affinity mask
- The CPUs associated with emulator pinning
- All online host CPUs
Later (once QEMU has allocated its memory) we then change this
again to (again in priority order):
- The CPUs associated with emulator pinning
- The CPUs returned by numad
- The CPUs associated with vCPU pinning
- All online host CPUs
Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com>
---
diff to v1 (both points suggested by Dan):
- Expanded the commit message
- fixed qemuProcessGetAllCpuAffinity so that it returns online CPU map
only
src/qemu/qemu_process.c | 132 +++++++++++++++++++---------------------
1 file changed, 63 insertions(+), 69 deletions(-)
Reviewed-by: Daniel P. Berrangé <berrange(a)redhat.com>
Regards,
Daniel
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