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.
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