On Thu, May 09, 2013 at 06:22:17PM +0800, Osier Yang wrote:
> When the numatune memory mode is not "strict", the cpuset.mems
> inherits the parent's setting, which causes problem like:
>
> % virsh dumpxml rhel6_local | grep interleave -2
> <vcpu placement='static'>2</vcpu>
> <numatune>
> <memory mode='interleave' nodeset='1-2'/>
> </numatune>
> <os>
>
> % cat /proc/3713/status | grep Mems_allowed_list
> Mems_allowed_list: 0-3
>
> % virsh numatune rhel6_local
> numa_mode : interleave
> numa_nodeset : 0-3
Yes the information is misleading.
>
> Though the domain process's memory binding is set with libnuma
> after the cgroup setting.
>
> The reason for only allowing "strict" mode in current code is the
> cpuset.mems doesn't understand the memory policy modes (interleave,
> prefered, strict), it actually equals to the "strict" mode ("strict"
> means the allocation will fail if the memory cannot be allocated on
> the target node. Default operation is to fall back to other nodes.
Default is localalloc.
> >From man numa(3)). However, writing the the cpuset.mems even if the
> numatune memory mode is not strict should be better than the blind
> inheritance anyway.
It's OK to interleave mode, combined with cpuset.memory_spread_xxx.
But what about preferred mode? comparing:
strict: Strict means the allocation will fail if the memory cannot be
allocated on the target node.
preferred: The system will attempt to allocate memory from the
preferred node, but will fall back to other nodes if no
memory is available on the the preferred node.
>
> ---
> However, I'm not comfortable with the solution, since anyway the
> modes except "strict" are not meaningful for cpuset.mems.
>
> Another problem what I'm not sure about is: If the cpuset.cpus will
> affect the libnuma setting? Assuming without this patch, domain
> process's cpuset.mems will be set as '0-7' (8 NUMA nodes, each has 8
> CPUs). And the numatune memory mode is "interleave", and libnuma set
> the memory binding as "1-2". Even with this patch applied, setting
> cpuset.mems as "1-2", any potential problem?
>
> So this patch is mainly for raising up the problem, and to see if
> guys have any opinions. @hutao, since these codes are from you, any
> opinions/idea? Thanks.
> ---
> src/qemu/qemu_cgroup.c | 18 +++++++++++++-----
> 1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/src/qemu/qemu_cgroup.c b/src/qemu/qemu_cgroup.c
> index 33eebd7..22fe25b 100644
> --- a/src/qemu/qemu_cgroup.c
> +++ b/src/qemu/qemu_cgroup.c
> @@ -597,11 +597,9 @@ qemuSetupCpusetCgroup(virDomainObjPtr vm,
> if (!virCgroupHasController(priv->cgroup, VIR_CGROUP_CONTROLLER_CPUSET))
> return 0;
>
> - if ((vm->def->numatune.memory.nodemask ||
> - (vm->def->numatune.memory.placement_mode ==
> - VIR_NUMA_TUNE_MEM_PLACEMENT_MODE_AUTO)) &&
> - vm->def->numatune.memory.mode == VIR_DOMAIN_NUMATUNE_MEM_STRICT) {
> -
> + if (vm->def->numatune.memory.nodemask ||
> + (vm->def->numatune.memory.placement_mode ==
> + VIR_NUMA_TUNE_MEM_PLACEMENT_MODE_AUTO)) {
> if (vm->def->numatune.memory.placement_mode ==
> VIR_NUMA_TUNE_MEM_PLACEMENT_MODE_AUTO)
> mem_mask = virBitmapFormat(nodemask);
> @@ -614,6 +612,16 @@ qemuSetupCpusetCgroup(virDomainObjPtr vm,
> goto cleanup;
> }
>
> + if (vm->def->numatune.memory.mode ==
> + VIR_DOMAIN_NUMATUNE_MEM_PREFERRED &&
> + strlen(mem_mask) != 1) {
> + virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> + _("NUMA memory tuning in 'preferred' mode "
> + "only supports single node"));
> + goto cleanup;
> +
> + }
> +
> rc = virCgroupSetCpusetMems(priv->cgroup, mem_mask);
>
> if (rc != 0) {
> --
> 1.8.1.4
>
> --
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