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tracing: Add lock-free tracing_map

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Add tracing_map, a special-purpose lock-free map for tracing.

tracing_map is designed to aggregate or 'sum' one or more values
associated with a specific object of type tracing_map_elt, which
is associated by the map to a given key.

It provides various hooks allowing per-tracer customization and is
separated out into a separate file in order to allow it to be shared
between multiple tracers, but isn't meant to be generally used outside
of that context.

The tracing_map implementation was inspired by lock-free map
algorithms originated by Dr. Cliff Click:

 http://www.azulsystems.com/blog/cliff/2007-03-26-non-blocking-hashtable
 http://www.azulsystems.com/events/javaone_2007/2007_LockFreeHash.pdf

Link: http://lkml.kernel.org/r/b43d68d1add33582a396f553c8ef705a33a6a748.1449767187.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Tom Zanussi 2015-12-10 12:50:50 -06:00 committed by Steven Rostedt
parent 540b589e63
commit 08d43a5fa0
4 changed files with 1354 additions and 0 deletions
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13
kernel/trace/Kconfig
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@ -528,6 +528,19 @@ config MMIOTRACE
See Documentation/trace/mmiotrace.txt.
If you are not helping to develop drivers, say N.
config TRACING_MAP
bool
depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
default n
help
tracing_map is a special-purpose lock-free map for tracing,
separated out as a stand-alone facility in order to allow it
to be shared between multiple tracers. It isn't meant to be
generally used outside of that context, and is normally
selected by tracers that use it.
If in doubt, say N.
config MMIOTRACE_TEST
tristate "Test module for mmiotrace"
depends on MMIOTRACE && m

1
kernel/trace/Makefile
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@ -31,6 +31,7 @@ obj-$(CONFIG_TRACING) += trace_output.o
obj-$(CONFIG_TRACING) += trace_seq.o
obj-$(CONFIG_TRACING) += trace_stat.o
obj-$(CONFIG_TRACING) += trace_printk.o
obj-$(CONFIG_TRACING_MAP) += tracing_map.o
obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o
obj-$(CONFIG_IRQSOFF_TRACER) += trace_irqsoff.o

1058
kernel/trace/tracing_map.c Normal file
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File diff suppressed because it is too large Load Diff

282
kernel/trace/tracing_map.h Normal file
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@ -0,0 +1,282 @@
#ifndef __TRACING_MAP_H
#define __TRACING_MAP_H
#define TRACING_MAP_BITS_DEFAULT 11
#define TRACING_MAP_BITS_MAX 17
#define TRACING_MAP_BITS_MIN 7
#define TRACING_MAP_FIELDS_MAX 4
#define TRACING_MAP_KEYS_MAX 2
#define TRACING_MAP_SORT_KEYS_MAX 2
typedef int (*tracing_map_cmp_fn_t) (void *val_a, void *val_b);
/*
* This is an overview of the tracing_map data structures and how they
* relate to the tracing_map API. The details of the algorithms
* aren't discussed here - this is just a general overview of the data
* structures and how they interact with the API.
*
* The central data structure of the tracing_map is an initially
* zeroed array of struct tracing_map_entry (stored in the map field
* of struct tracing_map). tracing_map_entry is a very simple data
* structure containing only two fields: a 32-bit unsigned 'key'
* variable and a pointer named 'val'. This array of struct
* tracing_map_entry is essentially a hash table which will be
* modified by a single function, tracing_map_insert(), but which can
* be traversed and read by a user at any time (though the user does
* this indirectly via an array of tracing_map_sort_entry - see the
* explanation of that data structure in the discussion of the
* sorting-related data structures below).
*
* The central function of the tracing_map API is
* tracing_map_insert(). tracing_map_insert() hashes the
* arbitrarily-sized key passed into it into a 32-bit unsigned key.
* It then uses this key, truncated to the array size, as an index
* into the array of tracing_map_entries. If the value of the 'key'
* field of the tracing_map_entry found at that location is 0, then
* that entry is considered to be free and can be claimed, by
* replacing the 0 in the 'key' field of the tracing_map_entry with
* the new 32-bit hashed key. Once claimed, that tracing_map_entry's
* 'val' field is then used to store a unique element which will be
* forever associated with that 32-bit hashed key in the
* tracing_map_entry.
*
* That unique element now in the tracing_map_entry's 'val' field is
* an instance of tracing_map_elt, where 'elt' in the latter part of
* that variable name is short for 'element'. The purpose of a
* tracing_map_elt is to hold values specific to the the particular
* 32-bit hashed key it's assocated with. Things such as the unique
* set of aggregated sums associated with the 32-bit hashed key, along
* with a copy of the full key associated with the entry, and which
* was used to produce the 32-bit hashed key.
*
* When tracing_map_create() is called to create the tracing map, the
* user specifies (indirectly via the map_bits param, the details are
* unimportant for this discussion) the maximum number of elements
* that the map can hold (stored in the max_elts field of struct
* tracing_map). This is the maximum possible number of
* tracing_map_entries in the tracing_map_entry array which can be
* 'claimed' as described in the above discussion, and therefore is
* also the maximum number of tracing_map_elts that can be associated
* with the tracing_map_entry array in the tracing_map. Because of
* the way the insertion algorithm works, the size of the allocated
* tracing_map_entry array is always twice the maximum number of
* elements (2 * max_elts). This value is stored in the map_size
* field of struct tracing_map.
*
* Because tracing_map_insert() needs to work from any context,
* including from within the memory allocation functions themselves,
* both the tracing_map_entry array and a pool of max_elts
* tracing_map_elts are pre-allocated before any call is made to
* tracing_map_insert().
*
* The tracing_map_entry array is allocated as a single block by
* tracing_map_create().
*
* Because the tracing_map_elts are much larger objects and can't
* generally be allocated together as a single large array without
* failure, they're allocated individually, by tracing_map_init().
*
* The pool of tracing_map_elts are allocated by tracing_map_init()
* rather than by tracing_map_create() because at the time
* tracing_map_create() is called, there isn't enough information to
* create the tracing_map_elts. Specifically,the user first needs to
* tell the tracing_map implementation how many fields the
* tracing_map_elts contain, and which types of fields they are (key
* or sum). The user does this via the tracing_map_add_sum_field()
* and tracing_map_add_key_field() functions, following which the user
* calls tracing_map_init() to finish up the tracing map setup. The
* array holding the pointers which make up the pre-allocated pool of
* tracing_map_elts is allocated as a single block and is stored in
* the elts field of struct tracing_map.
*
* There is also a set of structures used for sorting that might
* benefit from some minimal explanation.
*
* struct tracing_map_sort_key is used to drive the sort at any given
* time. By 'any given time' we mean that a different
* tracing_map_sort_key will be used at different times depending on
* whether the sort currently being performed is a primary or a
* secondary sort.
*
* The sort key is very simple, consisting of the field index of the
* tracing_map_elt field to sort on (which the user saved when adding
* the field), and whether the sort should be done in an ascending or
* descending order.
*
* For the convenience of the sorting code, a tracing_map_sort_entry
* is created for each tracing_map_elt, again individually allocated
* to avoid failures that might be expected if allocated as a single
* large array of struct tracing_map_sort_entry.
* tracing_map_sort_entry instances are the objects expected by the
* various internal sorting functions, and are also what the user
* ultimately receives after calling tracing_map_sort_entries().
* Because it doesn't make sense for users to access an unordered and
* sparsely populated tracing_map directly, the
* tracing_map_sort_entries() function is provided so that users can
* retrieve a sorted list of all existing elements. In addition to
* the associated tracing_map_elt 'elt' field contained within the
* tracing_map_sort_entry, which is the object of interest to the
* user, tracing_map_sort_entry objects contain a number of additional
* fields which are used for caching and internal purposes and can
* safely be ignored.
*/
struct tracing_map_field {
tracing_map_cmp_fn_t cmp_fn;
union {
atomic64_t sum;
unsigned int offset;
};
};
struct tracing_map_elt {
struct tracing_map *map;
struct tracing_map_field *fields;
void *key;
void *private_data;
};
struct tracing_map_entry {
u32 key;
struct tracing_map_elt *val;
};
struct tracing_map_sort_key {
unsigned int field_idx;
bool descending;
};
struct tracing_map_sort_entry {
void *key;
struct tracing_map_elt *elt;
bool elt_copied;
bool dup;
};
struct tracing_map_array {
unsigned int entries_per_page;
unsigned int entry_size_shift;
unsigned int entry_shift;
unsigned int entry_mask;
unsigned int n_pages;
void **pages;
};
#define TRACING_MAP_ARRAY_ELT(array, idx) \
(array->pages[idx >> array->entry_shift] + \
((idx & array->entry_mask) << array->entry_size_shift))
#define TRACING_MAP_ENTRY(array, idx) \
((struct tracing_map_entry *)TRACING_MAP_ARRAY_ELT(array, idx))
#define TRACING_MAP_ELT(array, idx) \
((struct tracing_map_elt **)TRACING_MAP_ARRAY_ELT(array, idx))
struct tracing_map {
unsigned int key_size;
unsigned int map_bits;
unsigned int map_size;
unsigned int max_elts;
atomic_t next_elt;
struct tracing_map_array *elts;
struct tracing_map_array *map;
const struct tracing_map_ops *ops;
void *private_data;
struct tracing_map_field fields[TRACING_MAP_FIELDS_MAX];
unsigned int n_fields;
int key_idx[TRACING_MAP_KEYS_MAX];
unsigned int n_keys;
struct tracing_map_sort_key sort_key;
atomic64_t hits;
atomic64_t drops;
};
/**
* struct tracing_map_ops - callbacks for tracing_map
*
* The methods in this structure define callback functions for various
* operations on a tracing_map or objects related to a tracing_map.
*
* For a detailed description of tracing_map_elt objects please see
* the overview of tracing_map data structures at the beginning of
* this file.
*
* All the methods below are optional.
*
* @elt_alloc: When a tracing_map_elt is allocated, this function, if
* defined, will be called and gives clients the opportunity to
* allocate additional data and attach it to the element
* (tracing_map_elt->private_data is meant for that purpose).
* Element allocation occurs before tracing begins, when the
* tracing_map_init() call is made by client code.
*
* @elt_copy: At certain points in the lifetime of an element, it may
* need to be copied. The copy should include a copy of the
* client-allocated data, which can be copied into the 'to'
* element from the 'from' element.
*
* @elt_free: When a tracing_map_elt is freed, this function is called
* and allows client-allocated per-element data to be freed.
*
* @elt_clear: This callback allows per-element client-defined data to
* be cleared, if applicable.
*
* @elt_init: This callback allows per-element client-defined data to
* be initialized when used i.e. when the element is actually
* claimed by tracing_map_insert() in the context of the map
* insertion.
*/
struct tracing_map_ops {
int (*elt_alloc)(struct tracing_map_elt *elt);
void (*elt_copy)(struct tracing_map_elt *to,
struct tracing_map_elt *from);
void (*elt_free)(struct tracing_map_elt *elt);
void (*elt_clear)(struct tracing_map_elt *elt);
void (*elt_init)(struct tracing_map_elt *elt);
};
extern struct tracing_map *
tracing_map_create(unsigned int map_bits,
unsigned int key_size,
const struct tracing_map_ops *ops,
void *private_data);
extern int tracing_map_init(struct tracing_map *map);
extern int tracing_map_add_sum_field(struct tracing_map *map);
extern int tracing_map_add_key_field(struct tracing_map *map,
unsigned int offset,
tracing_map_cmp_fn_t cmp_fn);
extern void tracing_map_destroy(struct tracing_map *map);
extern void tracing_map_clear(struct tracing_map *map);
extern struct tracing_map_elt *
tracing_map_insert(struct tracing_map *map, void *key);
extern struct tracing_map_elt *
tracing_map_lookup(struct tracing_map *map, void *key);
extern tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size,
int field_is_signed);
extern int tracing_map_cmp_string(void *val_a, void *val_b);
extern int tracing_map_cmp_none(void *val_a, void *val_b);
extern void tracing_map_update_sum(struct tracing_map_elt *elt,
unsigned int i, u64 n);
extern u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i);
extern void tracing_map_set_field_descr(struct tracing_map *map,
unsigned int i,
unsigned int key_offset,
tracing_map_cmp_fn_t cmp_fn);
extern int
tracing_map_sort_entries(struct tracing_map *map,
struct tracing_map_sort_key *sort_keys,
unsigned int n_sort_keys,
struct tracing_map_sort_entry ***sort_entries);
extern void
tracing_map_destroy_sort_entries(struct tracing_map_sort_entry **entries,
unsigned int n_entries);
#endif /* __TRACING_MAP_H */