mm,vmacache: add debug data
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@hp.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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 @@
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 @@
#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 99c8bfe..c2de650 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -501,6 +501,16 @@
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 1037a3ba..658ed3b 100644
--- a/mm/vmacache.c
+++ b/mm/vmacache.c
@@ -78,6 +78,8 @@
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];
@@ -85,8 +87,10 @@
continue;
if (WARN_ON_ONCE(vma->vm_mm != mm))
break;
- if (vma->vm_start <= addr && vma->vm_end > addr)
+ if (vma->vm_start <= addr && vma->vm_end > addr) {
+ count_vm_vmacache_event(VMACACHE_FIND_HITS);
return vma;
+ }
}
return NULL;
@@ -102,11 +106,15 @@
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 @@
"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 */