Introduce a CONFIG_DEBUG_VM_VMACACHE option to enable
counting the cache hit rate -- exported in /proc/vmstat.
Any updates to the caching scheme needs this kind of data,
thus it can save some work re-implementing the counting
all the time.
Signed-off-by: Davidlohr Bueso <davidlohr@xxxxxx>
---
include/linux/vm_event_item.h | 4 ++++
include/linux/vmstat.h | 6 ++++++
lib/Kconfig.debug | 10 ++++++++++
mm/vmacache.c | 9 ++++++++-
mm/vmstat.c | 4 ++++
5 files changed, 32 insertions(+), 1 deletion(-)
diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 486c397..ced9234 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -80,6 +80,10 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
NR_TLB_LOCAL_FLUSH_ALL,
NR_TLB_LOCAL_FLUSH_ONE,
#endif /* CONFIG_DEBUG_TLBFLUSH */
+#ifdef CONFIG_DEBUG_VM_VMACACHE
+ VMACACHE_FIND_CALLS,
+ VMACACHE_FIND_HITS,
+#endif
NR_VM_EVENT_ITEMS
};
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index 45c9cd1..82e7db7 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -95,6 +95,12 @@ static inline void vm_events_fold_cpu(int cpu)
#define count_vm_tlb_events(x, y) do { (void)(y); } while (0)
#endif
+#ifdef CONFIG_DEBUG_VM_VMACACHE
+#define count_vm_vmacache_event(x) count_vm_event(x)
+#else
+#define count_vm_vmacache_event(x) do {} while (0)
+#endif
+
#define __count_zone_vm_events(item, zone, delta) \
__count_vm_events(item##_NORMAL - ZONE_NORMAL + \
zone_idx(zone), delta)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 819ac51..9ed3d9b 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -501,6 +501,16 @@ config DEBUG_VM
If unsure, say N.
+config DEBUG_VM_VMACACHE
+ bool "Debug VMA caching"
+ depends on DEBUG_VM
+ help
+ Enable this to turn on VMA caching debug information. Doing so
+ can cause significant overhead, so only enable it in non-production
+ environments.
+
+ If unsure, say N.
+
config DEBUG_VM_RB
bool "Debug VM red-black trees"
depends on DEBUG_VM
diff --git a/mm/vmacache.c b/mm/vmacache.c
index d4224b3..e167da2 100644
--- a/mm/vmacache.c
+++ b/mm/vmacache.c
@@ -78,11 +78,14 @@ struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
if (!vmacache_valid(mm))
return NULL;
+ count_vm_vmacache_event(VMACACHE_FIND_CALLS);
+
for (i = 0; i < VMACACHE_SIZE; i++) {
struct vm_area_struct *vma = current->vmacache[i];
if (vma && vma->vm_start <= addr && vma->vm_end > addr) {
BUG_ON(vma->vm_mm != mm);
+ count_vm_vmacache_event(VMACACHE_FIND_HITS);
return vma;
}
}
@@ -100,11 +103,15 @@ struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
if (!vmacache_valid(mm))
return NULL;
+ count_vm_vmacache_event(VMACACHE_FIND_CALLS);
+
for (i = 0; i < VMACACHE_SIZE; i++) {
struct vm_area_struct *vma = current->vmacache[i];
- if (vma && vma->vm_start == start && vma->vm_end == end)
+ if (vma && vma->vm_start == start && vma->vm_end == end) {
+ count_vm_vmacache_event(VMACACHE_FIND_HITS);
return vma;
+ }
}
return NULL;
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 302dd07..82ce17c 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -866,6 +866,10 @@ const char * const vmstat_text[] = {
"nr_tlb_local_flush_one",
#endif /* CONFIG_DEBUG_TLBFLUSH */
+#ifdef CONFIG_DEBUG_VM_VMACACHE
+ "vmacache_find_calls",
+ "vmacache_find_hits",
+#endif
#endif /* CONFIG_VM_EVENTS_COUNTERS */
};
#endif /* CONFIG_PROC_FS || CONFIG_SYSFS || CONFIG_NUMA */
--
1.8.1.4
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