Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> writes: > On Tue, Jun 19, 2018 at 01:52:16PM +0100, Punit Agrawal wrote: >> Michal Hocko <mhocko@xxxxxxxxxx> writes: >> >> > On Tue 19-06-18 20:03:07, Xie XiuQi wrote: >> > [...] >> >> I tested on a arm board with 128 cores 4 numa nodes, but I set CONFIG_NR_CPUS=72. >> >> Then node 3 is not be created, because node 3 has no memory, and no cpu. >> >> But some pci device may related to node 3, which be set in ACPI table. >> > >> > Could you double check that zonelists for node 3 are generated >> > correctly? >> >> The cpus in node 3 aren't onlined and there's no memory attached - I >> suspect that no zonelists are built for this node. >> >> We skip creating a node, if the number of SRAT entries parsed exceeds >> NR_CPUS[0]. This in turn prevents onlining the numa node and so no >> zonelists will be created for it. >> >> I think the problem will go away if the cpus are restricted via the >> kernel command line by setting nr_cpus. >> >> Xie, can you try the below patch on top of the one enabling memoryless >> nodes? I'm not sure this is the right solution but at least it'll >> confirm the problem. > > This issue looks familiar (or at least related): > > git log d3bd058826aa Indeed. Thanks for digging into this. > > The reason why the NR_CPUS guard is there is to avoid overflowing > the early_node_cpu_hwid array. Ah right... I missed that. The below patch is definitely not what we want. > IA64 does something different in > that respect compared to x86, we have to have a look into this. > > Regardless, AFAICS the proximity domains to nodes mappings should not > depend on CONFIG_NR_CPUS, it seems that there is something wrong in that > in ARM64 ACPI SRAT parsing. Not only SRAT parsing but it looks like there is a similar restriction while parsing the ACPI MADT in acpi_map_gic_cpu_interface(). The incomplete parsing introduces a dependency on the ordering of entries being aligned between SRAT and MADT when NR_CPUS is restricted. We want to parse the entire table in both cases so that the code is robust to reordering of entries. In terms of $SUBJECT, I wonder if it's worth taking the original patch as a temporary fix (it'll also be easier to backport) while we work on fixing these other issues and enabling memoryless nodes.
