[libvirt] [PATCH 4/5] qemu: Build command line for NUMA tuning

[Osier Yang]

于 2011年05月05日 23:21, Daniel P. Berrange 写道:
> On Thu, May 05, 2011 at 05:38:29PM +0800, Osier Yang wrote:
>> Just prepend numactl command line to qemu command line.
>> ---
>>   src/qemu/qemu_command.c |   16 ++++++++++++++++
>>   1 files changed, 16 insertions(+), 0 deletions(-)
>>
>> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
>> index 2205ed1..156fdfb 100644
>> --- a/src/qemu/qemu_command.c
>> +++ b/src/qemu/qemu_command.c
>> @@ -2762,7 +2762,23 @@ qemuBuildCommandLine(virConnectPtr conn,
>>           break;
>>       }
>>
>> +#ifdef HAVE_NUMACTL
>> +    /* XXX: Logic here to build numactl commmand line need to be changed if
>> +     * more NUMA tuning related stuffs in future.
>> +     */
>> +    if (def->numatune.membind.nodeset) {
>> +        cmd = virCommandNewArgList(NUMACTL,
>> +                                   "-m",
>> +                                   def->numatune.membind.nodeset,
>> +                                   NULL);
>> +
>> +        virCommandAddArgList(cmd, emulator, "-S", NULL);
>> +    } else {
>> +        cmd = virCommandNewArgList(emulator, "-S", NULL);
>> +    }
>> +#else
>>       cmd = virCommandNewArgList(emulator, "-S", NULL);
>> +#endif
>
> NACK to this approach. We should be using the libnuma APIs to set the
> memory binding for the process directly, and not running the numactl
> command.

Hi, Dan,

I looked at libnuma API, it looks to me there is no API provided to
change the NUMA policy for process with specified PID,
like sched_setaffinity, think it's reasonable to not allow to set
the policy with specified PID, otherwise if one change the NUMA
policy for a process frequently, it will be pain for kernel.

AFAIK, If one wants to use libnuma to change a process' NUMA policy,
one way is to use libnuma in the codes of the program for which one
want to set the policy. The other way is to use numactl.

As qemu doesn't use libnuma to support NUMA tuning yet, IMHO what we
only can do is to use numactl if want to add support for NUMA tuning
currently.

Thanks,
Osier