Re: [REGRESSION] funny sched_domain build failure during resume

Peter Zijlstra
2014-05-14T14:00:42Z

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On Fri, May 09, 2014 at 12:04:55PM -0400, Tejun Heo wrote:
> Hello, guys.
>
> So, after resuming from suspend, I found my build jobs can not migrate
> away from the CPU it started on and thus just making use of single
> core. It turns out the scheduler failed to build sched domains due to
> order-3 allocation failure.
>
> systemd-sleep: page allocation failure: order:3, mode:0x104010
> CPU: 0 PID: 11648 Comm: systemd-sleep Not tainted 3.14.2-200.fc20.x86_64 #1
> Hardware name: System manufacturer System Product Name/P8Z68-V LX, BIOS 4105 07/01/2013
> 0000000000000000 000000001bc36890 ffff88009c2d5958 ffffffff816eec92
> 0000000000104010 ffff88009c2d59e8 ffffffff8117a32a 0000000000000000
> ffff88021efe6b00 0000000000000003 0000000000104010 ffff88009c2d59e8
> Call Trace:
> [<ffffffff816eec92>] dump_stack+0x45/0x56
> [<ffffffff8117a32a>] warn_alloc_failed+0xfa/0x170
> [<ffffffff8117e8f5>] __alloc_pages_nodemask+0x8e5/0xb00
> [<ffffffff811c0ce3>] alloc_pages_current+0xa3/0x170
> [<ffffffff811796a4>] __get_free_pages+0x14/0x50
> [<ffffffff8119823e>] kmalloc_order_trace+0x2e/0xa0
> [<ffffffff810c033f>] build_sched_domains+0x1ff/0xcc0
> [<ffffffff810c123e>] partition_sched_domains+0x35e/0x3d0
> [<ffffffff811168e7>] cpuset_update_active_cpus+0x17/0x40
> [<ffffffff810c130a>] cpuset_cpu_active+0x5a/0x70
> [<ffffffff816f9f4c>] notifier_call_chain+0x4c/0x70
> [<ffffffff810b2a1e>] __raw_notifier_call_chain+0xe/0x10
> [<ffffffff8108a413>] cpu_notify+0x23/0x50
> [<ffffffff8108a678>] _cpu_up+0x188/0x1a0
> [<ffffffff816e1783>] enable_nonboot_cpus+0x93/0xf0
> [<ffffffff810d9d45>] suspend_devices_and_enter+0x325/0x450
> [<ffffffff810d9fe8>] pm_suspend+0x178/0x260
> [<ffffffff810d8e79>] state_store+0x79/0xf0
> [<ffffffff81355bdf>] kobj_attr_store+0xf/0x20
> [<ffffffff81262c4d>] sysfs_kf_write+0x3d/0x50
> [<ffffffff81266b12>] kernfs_fop_write+0xd2/0x140
> [<ffffffff811e964a>] vfs_write+0xba/0x1e0
> [<ffffffff811ea0a5>] SyS_write+0x55/0xd0
> [<ffffffff816ff029>] system_call_fastpath+0x16/0x1b
>
> The allocation is from alloc_rootdomain().
>
> struct root_domain *rd;
>
> rd = kmalloc(sizeof(*rd), GFP_KERNEL);
>
> The thing is the system has plenty of reclaimable memory and shouldn't
> have any trouble satisfying one GFP_KERNEL order-3 allocation;
> however, the problem is that this is during resume and the devices
> haven't been woken up yet, so pm_restrict_gfp_mask() punches out
> GFP_IOFS from all allocation masks and the page allocator has just
> __GFP_WAIT to work with and, with enough bad luck, fails expectedly.
>
> The problem has always been there but seems to have been exposed by
> the addition of deadline scheduler support, which added cpudl to
> root_domain making it larger by around 20k bytes on my setup, making
> an order-3 allocation necessary during CPU online.
>
> It looks like the allocation is for a temp buffer and there are also
> percpu allocations going on. Maybe just allocate the buffers on boot
> and keep them around?
>
> Kudos to Johannes for helping deciphering mm debug messages.

Does something like the below help any? I noticed those things (cpudl
and cpupri) had [NR_CPUS] arrays, which is always 'fun'.

The below is a mostly no thought involved conversion of cpudl which
boots, I'll also do cpupri and then actually stare at the algorithms to
see if I didn't make any obvious fails.

Juri?

---
kernel/sched/cpudeadline.c | 29 +++++++++++++++++++----------
kernel/sched/cpudeadline.h | 6 +++---
2 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index ab001b5d5048..c34ab09a790b 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -13,6 +13,7 @@

#include <linux/gfp.h>
#include <linux/kernel.h>
+#include <linux/slab.h>
#include "cpudeadline.h"

static inline int parent(int i)
@@ -37,10 +38,7 @@ static inline int dl_time_before(u64 a, u64 b)

static void cpudl_exchange(struct cpudl *cp, int a, int b)
{
- int cpu_a = cp->elements[a].cpu, cpu_b = cp->elements[b].cpu;
-
swap(cp->elements[a], cp->elements[b]);
- swap(cp->cpu_to_idx[cpu_a], cp->cpu_to_idx[cpu_b]);
}

static void cpudl_heapify(struct cpudl *cp, int idx)
@@ -140,7 +138,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid)
WARN_ON(!cpu_present(cpu));

raw_spin_lock_irqsave(&cp->lock, flags);
- old_idx = cp->cpu_to_idx[cpu];
+ old_idx = cp->elements[cpu].idx;
if (!is_valid) {
/* remove item */
if (old_idx == IDX_INVALID) {
@@ -155,8 +153,8 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid)
cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl;
cp->elements[old_idx].cpu = new_cpu;
cp->size--;
- cp->cpu_to_idx[new_cpu] = old_idx;
- cp->cpu_to_idx[cpu] = IDX_INVALID;
+ cp->elements[new_cpu].idx = old_idx;
+ cp->elements[cpu].idx = IDX_INVALID;
while (old_idx > 0 && dl_time_before(
cp->elements[parent(old_idx)].dl,
cp->elements[old_idx].dl)) {
@@ -173,7 +171,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid)
cp->size++;
cp->elements[cp->size - 1].dl = 0;
cp->elements[cp->size - 1].cpu = cpu;
- cp->cpu_to_idx[cpu] = cp->size - 1;
+ cp->elements[cpu].idx = cp->size - 1;
cpudl_change_key(cp, cp->size - 1, dl);
cpumask_clear_cpu(cpu, cp->free_cpus);
} else {
@@ -195,10 +193,21 @@ int cpudl_init(struct cpudl *cp)
memset(cp, 0, sizeof(*cp));
raw_spin_lock_init(&cp->lock);
cp->size = 0;
- for (i = 0; i < NR_CPUS; i++)
- cp->cpu_to_idx[i] = IDX_INVALID;
- if (!alloc_cpumask_var(&cp->free_cpus, GFP_KERNEL))
+
+ cp->elements = kcalloc(num_possible_cpus(),
+ sizeof(struct cpudl_item),
+ GFP_KERNEL);
+ if (!cp->elements)
+ return -ENOMEM;
+
+ if (!alloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) {
+ kfree(cp->elements);
return -ENOMEM;
+ }
+
+ for_each_possible_cpu(i)
+ cp->elements[i].idx = IDX_INVALID;
+
cpumask_setall(cp->free_cpus);

return 0;
diff --git a/kernel/sched/cpudeadline.h b/kernel/sched/cpudeadline.h
index a202789a412c..538c9796ad4a 100644
--- a/kernel/sched/cpudeadline.h
+++ b/kernel/sched/cpudeadline.h
@@ -5,17 +5,17 @@

#define IDX_INVALID -1

-struct array_item {
+struct cpudl_item {
u64 dl;
int cpu;
+ int idx;
};

struct cpudl {
raw_spinlock_t lock;
int size;
- int cpu_to_idx[NR_CPUS];
- struct array_item elements[NR_CPUS];
cpumask_var_t free_cpus;
+ struct cpudl_item *elements;
};