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