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, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>