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sched/numa: Trace decisions related to skipping VMAs

Browse source 
NUMA balancing skips or scans VMAs for a variety of reasons. In preparation
for completing scans of VMAs regardless of PID access, trace the reasons
why a VMA was skipped. In a later patch, the tracing will be used to track
if a VMA was forcibly scanned.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231010083143.19593-4-mgorman@techsingularity.net
This commit is contained in:
Mel Gorman 2023-10-10 09:31:40 +01:00 committed by Ingo Molnar
parent f3a6c97940
commit ed2da8b725
3 changed files with 71 additions and 4 deletions
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8
include/linux/sched/numa_balancing.h
View file

@ -15,6 +15,14 @@
#define TNF_FAULT_LOCAL 0x08
#define TNF_MIGRATE_FAIL 0x10
enum numa_vmaskip_reason {
NUMAB_SKIP_UNSUITABLE,
NUMAB_SKIP_SHARED_RO,
NUMAB_SKIP_INACCESSIBLE,
NUMAB_SKIP_SCAN_DELAY,
NUMAB_SKIP_PID_INACTIVE,
};
#ifdef CONFIG_NUMA_BALANCING
extern void task_numa_fault(int last_node, int node, int pages, int flags);
extern pid_t task_numa_group_id(struct task_struct *p);

50
include/trace/events/sched.h
View file

@ -664,6 +664,56 @@ DEFINE_EVENT(sched_numa_pair_template, sched_swap_numa,
TP_ARGS(src_tsk, src_cpu, dst_tsk, dst_cpu)
);
#ifdef CONFIG_NUMA_BALANCING
#define NUMAB_SKIP_REASON \
EM( NUMAB_SKIP_UNSUITABLE, "unsuitable" ) \
EM( NUMAB_SKIP_SHARED_RO, "shared_ro" ) \
EM( NUMAB_SKIP_INACCESSIBLE, "inaccessible" ) \
EM( NUMAB_SKIP_SCAN_DELAY, "scan_delay" ) \
EMe(NUMAB_SKIP_PID_INACTIVE, "pid_inactive" )
/* Redefine for export. */
#undef EM
#undef EMe
#define EM(a, b) TRACE_DEFINE_ENUM(a);
#define EMe(a, b) TRACE_DEFINE_ENUM(a);
NUMAB_SKIP_REASON
/* Redefine for symbolic printing. */
#undef EM
#undef EMe
#define EM(a, b) { a, b },
#define EMe(a, b) { a, b }
TRACE_EVENT(sched_skip_vma_numa,
TP_PROTO(struct mm_struct *mm, struct vm_area_struct *vma,
enum numa_vmaskip_reason reason),
TP_ARGS(mm, vma, reason),
TP_STRUCT__entry(
__field(unsigned long, numa_scan_offset)
__field(unsigned long, vm_start)
__field(unsigned long, vm_end)
__field(enum numa_vmaskip_reason, reason)
),
TP_fast_assign(
__entry->numa_scan_offset = mm->numa_scan_offset;
__entry->vm_start = vma->vm_start;
__entry->vm_end = vma->vm_end;
__entry->reason = reason;
),
TP_printk("numa_scan_offset=%lX vm_start=%lX vm_end=%lX reason=%s",
__entry->numa_scan_offset,
__entry->vm_start,
__entry->vm_end,
__print_symbolic(__entry->reason, NUMAB_SKIP_REASON))
);
#endif /* CONFIG_NUMA_BALANCING */
/*
* Tracepoint for waking a polling cpu without an IPI.

17
kernel/sched/fair.c
View file

@ -3210,6 +3210,7 @@ static void task_numa_work(struct callback_head *work)
do {
if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_UNSUITABLE);
continue;
}
@ -3220,15 +3221,19 @@ static void task_numa_work(struct callback_head *work)
* as migrating the pages will be of marginal benefit.
*/
if (!vma->vm_mm ||
(vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
(vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ))) {
trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_SHARED_RO);
continue;
}
/*
* Skip inaccessible VMAs to avoid any confusion between
* PROT_NONE and NUMA hinting ptes
*/
if (!vma_is_accessible(vma))
if (!vma_is_accessible(vma)) {
trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_INACCESSIBLE);
continue;
}
/* Initialise new per-VMA NUMAB state. */
if (!vma->numab_state) {
@ -3250,12 +3255,16 @@ static void task_numa_work(struct callback_head *work)
* delay the scan for new VMAs.
*/
if (mm->numa_scan_seq && time_before(jiffies,
vma->numab_state->next_scan))
vma->numab_state->next_scan)) {
trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_SCAN_DELAY);
continue;
}
/* Do not scan the VMA if task has not accessed */
if (!vma_is_accessed(vma))
if (!vma_is_accessed(vma)) {
trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_PID_INACTIVE);
continue;
}
/*
* RESET access PIDs regularly for old VMAs. Resetting after checking