Re: [PATCH v3 0/5] Make cpuid <-> nodeid mapping persistent.

[Tang Chen]

On 11/24/2015 06:04 AM, Tejun Heo wrote:
> Hello,
>
> On Thu, Nov 19, 2015 at 12:22:10PM +0800, Tang Chen wrote:
> > [Solution]
> >
> > There are four mappings in the kernel:
> > 1. nodeid (logical node id)   <->   pxm
> > 2. apicid (physical cpu id)   <->   nodeid
> > 3. cpuid (logical cpu id)     <->   apicid
> > 4. cpuid (logical cpu id)     <->   nodeid
> >
> > 1. pxm (proximity domain) is provided by ACPI firmware in SRAT, and nodeid <-> pxm
> >     mapping is setup at boot time. This mapping is persistent, won't change.
> >
> > 2. apicid <-> nodeid mapping is setup using info in 1. The mapping is setup at boot
> >     time and CPU hotadd time, and cleared at CPU hotremove time. This mapping is also
> >     persistent.
> >
> > 3. cpuid <-> apicid mapping is setup at boot time and CPU hotadd time. cpuid is
> >     allocated, lower ids first, and released at CPU hotremove time, reused for other
> >     hotadded CPUs. So this mapping is not persistent.
> >
> > 4. cpuid <-> nodeid mapping is also setup at boot time and CPU hotadd time, and
> >     cleared at CPU hotremove time. As a result of 3, this mapping is not persistent.
> >
> > To fix this problem, we establish cpuid <-> nodeid mapping for all the possible
> > cpus at boot time, and make it persistent. And according to init_cpu_to_node(),
> > cpuid <-> nodeid mapping is based on apicid <-> nodeid mapping and cpuid <-> apicid
> > mapping. So the key point is obtaining all cpus' apicid.
> I don't know much about acpi so can't actually review the patches but
> the overall approach looks good to me.

Thank you, TJ. Will test it recently.

> Thanks.


--
This message has been scanned for viruses and
dangerous content by Fujitsu, and is believed to be clean.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/