We want to filter out page_owner output and print only those
stacks that have been repeated beyond a certain threshold.
This gives us the chance to get rid of a lot of noise.
In order to do that, we need to keep track of how many repeated stacks
(for allocation) do we have, so we add a new refcount_t field
in the stack_record struct.
Note that this might increase the size of the struct for some
architectures.
E.g: x86_64 is not affected due to alignment, but x86 32bits might.
The alternative would be to have some kind of struct like this:
struct track_stacks {
struct stack_record *stack;
struct track_stacks *next;
refcount_t stack_count;
But ithat would imply to perform more allocations and glue everything
together, which would make the code more complex, so I think that
going with a new field in the struct stack_record is good enough.
Note that on __set_page_owner_handle(), page_owner->handle is set,
and on __reset_page_owner(), page_owner->free_handle is set.
We are interested in page_owner->handle, so when __set_page_owner()
gets called, we derive the stack_record struct from page_owner->handle,
and we increment its refcount_t field; and when __reset_page_owner()
gets called, we derive its stack_record from page_owner->handle()
and we decrement its refcount_t field.
Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
---
include/linux/stackdepot.h | 13 ++++++-
lib/stackdepot.c | 79 +++++++++++++++++++++++++++++++-------
mm/kasan/common.c | 3 +-
mm/page_owner.c | 14 +++++--
4 files changed, 89 insertions(+), 20 deletions(-)
diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
index bc2797955de9..4e3a88f135ee 100644
--- a/include/linux/stackdepot.h
+++ b/include/linux/stackdepot.h
@@ -15,9 +15,16 @@
typedef u32 depot_stack_handle_t;
+enum stack_depot_action {
+ STACK_DEPOT_ACTION_NONE,
+ STACK_DEPOT_ACTION_COUNT,
+};
+
depot_stack_handle_t __stack_depot_save(unsigned long *entries,
unsigned int nr_entries,
- gfp_t gfp_flags, bool can_alloc);
+ gfp_t gfp_flags, bool can_alloc,
+ enum stack_depot_action action);
+void stack_depot_dec_count(depot_stack_handle_t handle);
/*
* Every user of stack depot has to call stack_depot_init() during its own init
@@ -55,6 +62,10 @@ static inline int stack_depot_early_init(void) { return 0; }
depot_stack_handle_t stack_depot_save(unsigned long *entries,
unsigned int nr_entries, gfp_t gfp_flags);
+depot_stack_handle_t stack_depot_save_action(unsigned long *entries,
+ unsigned int nr_entries,
+ gfp_t gfp_flags,
+ enum stack_depot_action action);
unsigned int stack_depot_fetch(depot_stack_handle_t handle,
unsigned long **entries);
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index e73fda23388d..a806ef58a385 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -64,6 +64,7 @@ struct stack_record {
u32 hash; /* Hash in the hastable */
u32 size; /* Number of frames in the stack */
union handle_parts handle;
+ refcount_t count; /* Number of the same repeated stacks */
unsigned long entries[]; /* Variable-sized array of entries. */
};
@@ -140,6 +141,7 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
stack->handle.slabindex = depot_index;
stack->handle.offset = depot_offset >> STACK_ALLOC_ALIGN;
stack->handle.valid = 1;
+ refcount_set(&stack->count, 1);
memcpy(stack->entries, entries, flex_array_size(stack, entries, size));
depot_offset += required_size;
@@ -341,6 +343,29 @@ void stack_depot_print(depot_stack_handle_t stack)
}
EXPORT_SYMBOL_GPL(stack_depot_print);
+static struct stack_record *stack_depot_getstack(depot_stack_handle_t handle)
+{
+ union handle_parts parts = { .handle = handle };
+ void *slab;
+ size_t offset = parts.offset << STACK_ALLOC_ALIGN;
+ struct stack_record *stack;
+
+ if(!handle)
+ return NULL;
+
+ if (parts.slabindex > depot_index) {
+ WARN(1, "slab index %d out of bounds (%d) for stack id %08x\n",
+ parts.slabindex, depot_index, handle);
+ return NULL;
+ }
+ slab = stack_slabs[parts.slabindex];
+ if (!slab)
+ return NULL;
+
+ stack = slab + offset;
+ return stack;
+}
+
/**
* stack_depot_fetch - Fetch stack entries from a depot
*
@@ -353,30 +378,42 @@ EXPORT_SYMBOL_GPL(stack_depot_print);
unsigned int stack_depot_fetch(depot_stack_handle_t handle,
unsigned long **entries)
{
- union handle_parts parts = { .handle = handle };
- void *slab;
- size_t offset = parts.offset << STACK_ALLOC_ALIGN;
struct stack_record *stack;
*entries = NULL;
if (!handle)
return 0;
- if (parts.slabindex > depot_index) {
- WARN(1, "slab index %d out of bounds (%d) for stack id %08x\n",
- parts.slabindex, depot_index, handle);
- return 0;
- }
- slab = stack_slabs[parts.slabindex];
- if (!slab)
+ stack = stack_depot_getstack(handle);
+ if (!stack)
return 0;
- stack = slab + offset;
*entries = stack->entries;
return stack->size;
}
EXPORT_SYMBOL_GPL(stack_depot_fetch);
+static void stack_depot_inc_count(struct stack_record *stack)
+{
+ refcount_inc(&stack->count);
+}
+
+void stack_depot_dec_count(depot_stack_handle_t handle)
+{
+ struct stack_record *stack = NULL;
+
+ stack = stack_depot_getstack(handle);
+ if (stack) {
+ /*
+ * page_owner creates some stacks via create_dummy_stack().
+ * We are not interested in those, so make sure we only decrement
+ * "valid" stacks.
+ */
+ if (refcount_read(&stack->count) > 1)
+ refcount_dec(&stack->count);
+ }
+}
+
/**
* __stack_depot_save - Save a stack trace from an array
*
@@ -402,7 +439,8 @@ EXPORT_SYMBOL_GPL(stack_depot_fetch);
*/
depot_stack_handle_t __stack_depot_save(unsigned long *entries,
unsigned int nr_entries,
- gfp_t alloc_flags, bool can_alloc)
+ gfp_t alloc_flags, bool can_alloc,
+ enum stack_depot_action action)
{
struct stack_record *found = NULL, **bucket;
depot_stack_handle_t retval = 0;
@@ -488,8 +526,11 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
/* Nobody used this memory, ok to free it. */
free_pages((unsigned long)prealloc, STACK_ALLOC_ORDER);
}
- if (found)
+ if (found) {
retval = found->handle.handle;
+ if (action == STACK_DEPOT_ACTION_COUNT)
+ stack_depot_inc_count(found);
+ }
fast_exit:
return retval;
}
@@ -511,6 +552,16 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries,
unsigned int nr_entries,
gfp_t alloc_flags)
{
- return __stack_depot_save(entries, nr_entries, alloc_flags, true);
+ return __stack_depot_save(entries, nr_entries, alloc_flags, true,
+ STACK_DEPOT_ACTION_NONE);
}
EXPORT_SYMBOL_GPL(stack_depot_save);
+
+depot_stack_handle_t stack_depot_save_action(unsigned long *entries,
+ unsigned int nr_entries,
+ gfp_t alloc_flags,
+ enum stack_depot_action action)
+{
+ return __stack_depot_save(entries, nr_entries, alloc_flags, true, action);
+}
+EXPORT_SYMBOL_GPL(stack_depot_save_action);
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 69f583855c8b..8077c6e70815 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -36,7 +36,8 @@ depot_stack_handle_t kasan_save_stack(gfp_t flags, bool can_alloc)
unsigned int nr_entries;
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
- return __stack_depot_save(entries, nr_entries, flags, can_alloc);
+ return __stack_depot_save(entries, nr_entries, flags, can_alloc,
+ STACK_DEPOT_ACTION_NONE);
}
void kasan_set_track(struct kasan_track *track, gfp_t flags)
diff --git a/mm/page_owner.c b/mm/page_owner.c
index e4c6f3f1695b..8730f377fa91 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -106,7 +106,8 @@ static inline struct page_owner *get_page_owner(struct page_ext *page_ext)
return (void *)page_ext + page_owner_ops.offset;
}
-static noinline depot_stack_handle_t save_stack(gfp_t flags)
+static noinline depot_stack_handle_t save_stack(gfp_t flags,
+ enum stack_depot_action action)
{
unsigned long entries[PAGE_OWNER_STACK_DEPTH];
depot_stack_handle_t handle;
@@ -125,7 +126,7 @@ static noinline depot_stack_handle_t save_stack(gfp_t flags)
current->in_page_owner = 1;
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
- handle = stack_depot_save(entries, nr_entries, flags);
+ handle = stack_depot_save_action(entries, nr_entries, flags, action);
if (!handle)
handle = failure_handle;
@@ -138,6 +139,7 @@ void __reset_page_owner(struct page *page, unsigned short order)
int i;
struct page_ext *page_ext;
depot_stack_handle_t handle;
+ depot_stack_handle_t alloc_handle;
struct page_owner *page_owner;
u64 free_ts_nsec = local_clock();
@@ -145,7 +147,10 @@ void __reset_page_owner(struct page *page, unsigned short order)
if (unlikely(!page_ext))
return;
- handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
+ page_owner = get_page_owner(page_ext);
+ alloc_handle = page_owner->handle;
+
+ handle = save_stack(GFP_NOWAIT | __GFP_NOWARN, STACK_DEPOT_ACTION_NONE);
for (i = 0; i < (1 << order); i++) {
__clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
page_owner = get_page_owner(page_ext);
@@ -153,6 +158,7 @@ void __reset_page_owner(struct page *page, unsigned short order)
page_owner->free_ts_nsec = free_ts_nsec;
page_ext = page_ext_next(page_ext);
}
+ stack_depot_dec_count(alloc_handle);
}
static inline void __set_page_owner_handle(struct page_ext *page_ext,
@@ -189,7 +195,7 @@ noinline void __set_page_owner(struct page *page, unsigned short order,
if (unlikely(!page_ext))
return;
- handle = save_stack(gfp_mask);
+ handle = save_stack(gfp_mask, STACK_DEPOT_ACTION_COUNT);
__set_page_owner_handle(page_ext, handle, order, gfp_mask);
}
--
2.35.3
