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mm,vmacache: add debug data

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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>
This commit is contained in:
Davidlohr Bueso 2014-06-04 16:06:46 -07:00 committed by Linus Torvalds
parent 6f04f48dc9
commit 4f115147ff
5 changed files with 34 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/vm_event_item.h
View File

@ -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
};

6
include/linux/vmstat.h
View File

@ -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)

10
lib/Kconfig.debug
View File

@ -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

12
mm/vmacache.c
View File

@ -78,6 +78,8 @@ 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];
@ -85,8 +87,10 @@ struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
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 @@ 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;

4
mm/vmstat.c
View File

@ -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 */