On Thu, Feb 17, 2022 at 06:56:52PM -0000, tip-bot2 for Huang Ying wrote: > The following commit has been merged into the sched/core branch of tip: > > Commit-ID: 5c7b1aaf139dab5072311853bacc40fc3457d1f9 > Gitweb: https://git.kernel.org/tip/5c7b1aaf139dab5072311853bacc40fc3457d1f9 > Author: Huang Ying <ying.huang@xxxxxxxxx> > AuthorDate: Mon, 14 Feb 2022 20:15:53 +08:00 > Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > CommitterDate: Wed, 16 Feb 2022 15:57:53 +01:00 > > sched/numa: Avoid migrating task to CPU-less node > > In a typical memory tiering system, there's no CPU in slow (PMEM) NUMA > nodes. But if the number of the hint page faults on a PMEM node is > the max for a task, The current NUMA balancing policy may try to place > the task on the PMEM node instead of DRAM node. This is unreasonable, > because there's no CPU in PMEM NUMA nodes. To fix this, CPU-less > nodes are ignored when searching the migration target node for a task > in this patch. > > To test the patch, we run a workload that accesses more memory in PMEM > node than memory in DRAM node. Without the patch, the PMEM node will > be chosen as preferred node in task_numa_placement(). While the DRAM > node will be chosen instead with the patch. > > Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> > Link: https://lkml.kernel.org/r/20220214121553.582248-2-ying.huang@xxxxxxxxx Reverting this commit on the top of today's linux-next fixed a boot crash on arm64 NUMA systems. Unable to handle kernel paging request at virtual address ffff7a6601694aec KASAN: maybe wild-memory-access in range [0xffffd3300b4a5760-0xffffd3300b4a5767] Mem abort info: ESR = 0x96000005 EC = 0x25: DABT (current EL), IL = 32 bits mlx5_core 0007:02:00.0: enabling device (0100 -> 0102) SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault Data abort info: ISV = 0, ISS = 0x00000005 CM = 0, WnR = 0 swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000400b3d6c6000 [ffff7a6601694aec] pgd=0000403fc007f003, p4d=0000403fc007f003, pud=0000000000000000 Internal error: Oops: 96000005 [#1] PREEMPT SMP Modules linked in: nouveau(+) drm_ttm_helper ttm nvme(+) drm_dp_helper drm_kms_helper mlx5_core(+) mpt3sas(+) xhci_pci(+) nvme_core raid_class xhci_pci_renesas drm CPU: 85 PID: 1308 Comm: udevadm Not tainted 5.17.0-rc6-next-20220301 #1 pstate: 40400009 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : task_numa_placement lr : task_numa_placement sp : ffff800031047760 x29: ffff800031047760 x28: ffff3fffab916c00 x27: 0000000000000020 x26: 0000000000000001 x25: 0000000000000000 x24: 0000000000000000 x23: ffff07ffe5289a80 x22: ffffd3300b4a5760 x21: 000000000000003f x20: ffffd32feb4a5768 x19: 0000000000000000 x18: ffff07ffe528ad88 x17: ffffd32fe5693a1c x16: 0000000000000000 x15: ffff8000310478e0 x14: ffff07ffe528ad90 x13: 0000000000000002 x12: dfff80000000000d x11: 0000000000000001 x10: 000000000000b6be x9 : 0000000000000000 x8 : 00000000ffffffff x7 : ffffd32feb4a5780 x6 : 0000000000000000 x5 : 0000000000000000 x4 : 0000000000000000 x3 : 1ffffa6601694aec x2 : 0000000000000000 x1 : dfff800000000000 x0 : 000000001ffffff8 Call trace: task_numa_placement arch_test_bit at include/asm-generic/bitops/non-atomic.h:118 (inlined by) node_state at include/linux/nodemask.h:416 (inlined by) task_numa_placement at kernel/sched/fair.c:2439 task_numa_fault do_numa_page handle_pte_fault __handle_mm_fault handle_mm_fault do_page_fault do_translation_fault do_mem_abort el0_da el0t_64_sync_handler el0t_64_sync Code: 8b000296 d2d00001 f2fbffe1 d343fec3 (38e16861) ---[ end trace 0000000000000000 ]--- Kernel panic - not syncing: Oops: Fatal exception SMP: stopping secondary CPUs Kernel Offset: 0x532fdcf70000 from 0xffff800008000000 PHYS_OFFSET: 0x80000000 CPU features: 0x00,00042c0c,19801c82 Memory Limit: none ---[ end Kernel panic - not syncing: Oops: Fatal exception ]--- > --- > kernel/sched/fair.c | 25 ++++++++++++++++++++----- > 1 file changed, 20 insertions(+), 5 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index da3230b..11a72e1 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -1989,7 +1989,7 @@ static int task_numa_migrate(struct task_struct *p) > */ > ng = deref_curr_numa_group(p); > if (env.best_cpu == -1 || (ng && ng->active_nodes > 1)) { > - for_each_online_node(nid) { > + for_each_node_state(nid, N_CPU) { > if (nid == env.src_nid || nid == p->numa_preferred_nid) > continue; > > @@ -2087,13 +2087,13 @@ static void numa_group_count_active_nodes(struct numa_group *numa_group) > unsigned long faults, max_faults = 0; > int nid, active_nodes = 0; > > - for_each_online_node(nid) { > + for_each_node_state(nid, N_CPU) { > faults = group_faults_cpu(numa_group, nid); > if (faults > max_faults) > max_faults = faults; > } > > - for_each_online_node(nid) { > + for_each_node_state(nid, N_CPU) { > faults = group_faults_cpu(numa_group, nid); > if (faults * ACTIVE_NODE_FRACTION > max_faults) > active_nodes++; > @@ -2247,7 +2247,7 @@ static int preferred_group_nid(struct task_struct *p, int nid) > > dist = sched_max_numa_distance; > > - for_each_online_node(node) { > + for_each_node_state(node, N_CPU) { > score = group_weight(p, node, dist); > if (score > max_score) { > max_score = score; > @@ -2266,7 +2266,7 @@ static int preferred_group_nid(struct task_struct *p, int nid) > * inside the highest scoring group of nodes. The nodemask tricks > * keep the complexity of the search down. > */ > - nodes = node_online_map; > + nodes = node_states[N_CPU]; > for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) { > unsigned long max_faults = 0; > nodemask_t max_group = NODE_MASK_NONE; > @@ -2405,6 +2405,21 @@ static void task_numa_placement(struct task_struct *p) > } > } > > + /* Cannot migrate task to CPU-less node */ > + if (!node_state(max_nid, N_CPU)) { > + int near_nid = max_nid; > + int distance, near_distance = INT_MAX; > + > + for_each_node_state(nid, N_CPU) { > + distance = node_distance(max_nid, nid); > + if (distance < near_distance) { > + near_nid = nid; > + near_distance = distance; > + } > + } > + max_nid = near_nid; > + } > + > if (ng) { > numa_group_count_active_nodes(ng); > spin_unlock_irq(group_lock);
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