[tip: sched/core] sched/numa: Avoid migrating task to CPU-less node
Qian Cai
quic_qiancai at quicinc.com
Tue Mar 1 12:54:09 PST 2022
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 at intel.com>
> AuthorDate: Mon, 14 Feb 2022 20:15:53 +08:00
> Committer: Peter Zijlstra <peterz at infradead.org>
> 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 at intel.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
> Link: https://lkml.kernel.org/r/20220214121553.582248-2-ying.huang@intel.com
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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