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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Jul 2025 04:28:17.6451 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 28570672-34dc-4323-5d46-08ddc80f043f X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SJ1PEPF000023D7.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR12MB6742 Hello Leon, On 7/20/2025 4:11 PM, Leon Romanovsky wrote: > On Wed, Jul 09, 2025 at 04:19:17PM +0000, K Prateek Nayak wrote: >> Leon noted a topology_span_sane() warning in their guest deployment >> starting from v6.16-rc1 [1]. Debug that followed pointed to the >> tl->mask() for the NODE domain being incorrectly resolved to that of the >> highest NUMA domain. >> >> tl->mask() for NODE is set to the sd_numa_mask() which depends on the >> global "sched_domains_curr_level" hack. "sched_domains_curr_level" is >> set to the "tl->numa_level" during tl traversal in build_sched_domains() >> calling sd_init() but was not reset before topology_span_sane(). >> >> Since "tl->numa_level" still reflected the old value from >> build_sched_domains(), topology_span_sane() for the NODE domain trips >> when the span of the last NUMA domain overlaps. >> >> Instead of replicating the "sched_domains_curr_level" hack, Valentin >> suggested using the spans from the sched_domain objects constructed >> during build_sched_domains() which can also catch overlaps when the >> domain spans are fixed up by build_sched_domain(). >> >> Since build_sched_domain() is skipped when tl->mask() of a child domain >> already covers the entire cpumap, skip the domains that have an empty >> span. >> >> The original warning was reproducible on the following NUMA topology >> reported by Leon: >> >> $ sudo numactl -H >> available: 5 nodes (0-4) >> node 0 cpus: 0 1 >> node 0 size: 2927 MB >> node 0 free: 1603 MB >> node 1 cpus: 2 3 >> node 1 size: 3023 MB >> node 1 free: 3008 MB >> node 2 cpus: 4 5 >> node 2 size: 3023 MB >> node 2 free: 3007 MB >> node 3 cpus: 6 7 >> node 3 size: 3023 MB >> node 3 free: 3002 MB >> node 4 cpus: 8 9 >> node 4 size: 3022 MB >> node 4 free: 2718 MB >> node distances: >> node 0 1 2 3 4 >> 0: 10 39 38 37 36 >> 1: 39 10 38 37 36 >> 2: 38 38 10 37 36 >> 3: 37 37 37 10 36 >> 4: 36 36 36 36 10 >> >> The above topology can be mimicked using the following QEMU cmd that was >> used to reproduce the warning and test the fix: >> >> sudo qemu-system-x86_64 -enable-kvm -cpu host \ >> -m 20G -smp cpus=10,sockets=10 -machine q35 \ >> -object memory-backend-ram,size=4G,id=m0 \ >> -object memory-backend-ram,size=4G,id=m1 \ >> -object memory-backend-ram,size=4G,id=m2 \ >> -object memory-backend-ram,size=4G,id=m3 \ >> -object memory-backend-ram,size=4G,id=m4 \ >> -numa node,cpus=0-1,memdev=m0,nodeid=0 \ >> -numa node,cpus=2-3,memdev=m1,nodeid=1 \ >> -numa node,cpus=4-5,memdev=m2,nodeid=2 \ >> -numa node,cpus=6-7,memdev=m3,nodeid=3 \ >> -numa node,cpus=8-9,memdev=m4,nodeid=4 \ >> -numa dist,src=0,dst=1,val=39 \ >> -numa dist,src=0,dst=2,val=38 \ >> -numa dist,src=0,dst=3,val=37 \ >> -numa dist,src=0,dst=4,val=36 \ >> -numa dist,src=1,dst=0,val=39 \ >> -numa dist,src=1,dst=2,val=38 \ >> -numa dist,src=1,dst=3,val=37 \ >> -numa dist,src=1,dst=4,val=36 \ >> -numa dist,src=2,dst=0,val=38 \ >> -numa dist,src=2,dst=1,val=38 \ >> -numa dist,src=2,dst=3,val=37 \ >> -numa dist,src=2,dst=4,val=36 \ >> -numa dist,src=3,dst=0,val=37 \ >> -numa dist,src=3,dst=1,val=37 \ >> -numa dist,src=3,dst=2,val=37 \ >> -numa dist,src=3,dst=4,val=36 \ >> -numa dist,src=4,dst=0,val=36 \ >> -numa dist,src=4,dst=1,val=36 \ >> -numa dist,src=4,dst=2,val=36 \ >> -numa dist,src=4,dst=3,val=36 \ >> ... >> >> Suggested-by: Valentin Schneider >> Reported-by: Leon Romanovsky >> Closes: https://lore.kernel.org/lkml/20250610110701.GA256154@unreal/ [1] >> Fixes: ccf74128d66c ("sched/topology: Assert non-NUMA topology masks don't (partially) overlap") # ce29a7da84cd, f55dac1dafb3 >> Reviewed-by: Steve Wahl >> Tested-by: Valentin Schneider >> Reviewed-by: Valentin Schneider >> Signed-off-by: K Prateek Nayak >> --- >> Changes are based on tip:sched/urgent at commit fc975cfb3639 >> ("sched/deadline: Fix dl_server runtime calculation formula") > > Was this patch picked? Not yet. I think Peter was planning to pick it up as v6.17 material. P.S. The latest version v5 can be found at https://lore.kernel.org/lkml/20250715040824.893-1-kprateek.nayak@amd.com/ It is basically v4 but rebased on top of tip:sched/core to resolve conflicts with a recent cleanup. > > Thanks, > Tested-by: Leon Romanovsky Thanks a ton! -- Thanks and Regards, Prateek