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authorMarco Elver <elver@google.com>2021-11-05 13:45:28 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-11-06 13:30:43 -0700
commit9a19aeb5665068c3e2727230588684aae2cab7ef (patch)
tree7b3ed9c006eff9474397ba46a9a48c99041fe07b
parentf39f21b3ddc7fc0f87eb6dc75ddc81b5bbfb7672 (diff)
kfence: count unexpectedly skipped allocations
Maintain a counter to count allocations that are skipped due to being incompatible (oversized, incompatible gfp flags) or no capacity. This is to compute the fraction of allocations that could not be serviced by KFENCE, which we expect to be rare. Link: https://lkml.kernel.org/r/20210923104803.2620285-2-elver@google.com Signed-off-by: Marco Elver <elver@google.com> Reviewed-by: Dmitry Vyukov <dvyukov@google.com> Acked-by: Alexander Potapenko <glider@google.com> Cc: Aleksandr Nogikh <nogikh@google.com> Cc: Jann Horn <jannh@google.com> Cc: Taras Madan <tarasmadan@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/kfence/core.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 7a97db8bc8e7..249d75b7e5ee 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -112,6 +112,8 @@ enum kfence_counter_id {
KFENCE_COUNTER_FREES,
KFENCE_COUNTER_ZOMBIES,
KFENCE_COUNTER_BUGS,
+ KFENCE_COUNTER_SKIP_INCOMPAT,
+ KFENCE_COUNTER_SKIP_CAPACITY,
KFENCE_COUNTER_COUNT,
};
static atomic_long_t counters[KFENCE_COUNTER_COUNT];
@@ -121,6 +123,8 @@ static const char *const counter_names[] = {
[KFENCE_COUNTER_FREES] = "total frees",
[KFENCE_COUNTER_ZOMBIES] = "zombie allocations",
[KFENCE_COUNTER_BUGS] = "total bugs",
+ [KFENCE_COUNTER_SKIP_INCOMPAT] = "skipped allocations (incompatible)",
+ [KFENCE_COUNTER_SKIP_CAPACITY] = "skipped allocations (capacity)",
};
static_assert(ARRAY_SIZE(counter_names) == KFENCE_COUNTER_COUNT);
@@ -271,8 +275,10 @@ static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t g
list_del_init(&meta->list);
}
raw_spin_unlock_irqrestore(&kfence_freelist_lock, flags);
- if (!meta)
+ if (!meta) {
+ atomic_long_inc(&counters[KFENCE_COUNTER_SKIP_CAPACITY]);
return NULL;
+ }
if (unlikely(!raw_spin_trylock_irqsave(&meta->lock, flags))) {
/*
@@ -740,8 +746,10 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
* Perform size check before switching kfence_allocation_gate, so that
* we don't disable KFENCE without making an allocation.
*/
- if (size > PAGE_SIZE)
+ if (size > PAGE_SIZE) {
+ atomic_long_inc(&counters[KFENCE_COUNTER_SKIP_INCOMPAT]);
return NULL;
+ }
/*
* Skip allocations from non-default zones, including DMA. We cannot
@@ -749,8 +757,10 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
* properties (e.g. reside in DMAable memory).
*/
if ((flags & GFP_ZONEMASK) ||
- (s->flags & (SLAB_CACHE_DMA | SLAB_CACHE_DMA32)))
+ (s->flags & (SLAB_CACHE_DMA | SLAB_CACHE_DMA32))) {
+ atomic_long_inc(&counters[KFENCE_COUNTER_SKIP_INCOMPAT]);
return NULL;
+ }
/*
* allocation_gate only needs to become non-zero, so it doesn't make