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Date: Thu, 16 Jul 2015 23:25:54 +0000 (UTC)
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Tom Zanussi <tom.zanussi@...ux.intel.com>
Cc: rostedt@...dmis.org, daniel.wagner@...-carit.de,
masami.hiramatsu.pt@...achi.com, namhyung@...nel.org,
josh@...htriplett.org, andi@...stfloor.org,
linux-kernel@...r.kernel.org,
Julien Desfossez <jdesfossez@...icios.com>
Subject: Re: [PATCH v9 07/22] tracing: Add lock-free tracing_map
* Tom Zanussi wrote:
>> 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
Hi Tom,
First question: what is the rationale for implementing another
hash table from scratch here ? What is missing in the pre-existing
hash table implementations ?
Moreover, you might want to handle the case where jhash() returns
0. AFAIU, there is a race on "insert" in this scenario.
Thanks,
Mathieu
>>
>> Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
>> ---
>> kernel/trace/Makefile | 1 +
>> kernel/trace/tracing_map.c | 935 +++++++++++++++++++++++++++++++++++++++++++++
>> kernel/trace/tracing_map.h | 258 +++++++++++++
>> 3 files changed, 1194 insertions(+)
>> create mode 100644 kernel/trace/tracing_map.c
>> create mode 100644 kernel/trace/tracing_map.h
>>
>> diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
>> index 9b1044e..3b26cfb 100644
>> --- a/kernel/trace/Makefile
>> +++ b/kernel/trace/Makefile
>> @@ -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-$(CONFIG_TRACING) += tracing_map.o
>> obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
>> obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o
>> obj-$(CONFIG_IRQSOFF_TRACER) += trace_irqsoff.o
>> diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c
>> new file mode 100644
>> index 0000000..a505025
>> --- /dev/null
>> +++ b/kernel/trace/tracing_map.c
>> @@ -0,0 +1,935 @@
>> +/*
>> + * tracing_map - lock-free map for tracing
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License as published by
>> + * the Free Software Foundation; either version 2 of the License, or
>> + * (at your option) any later version.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>> + * GNU General Public License for more details.
>> + *
>> + * Copyright (C) 2015 Tom Zanussi <tom.zanussi@...ux.intel.com>
>> + *
>> + * tracing_map implementation 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
>> + */
>> +
>> +#include <linux/slab.h>
>> +#include <linux/jhash.h>
>> +#include <linux/sort.h>
>> +
>> +#include "tracing_map.h"
>> +#include "trace.h"
>> +
>> +/*
>> + * NOTE: For a detailed description of the data structures used by
>> + * these functions (such as tracing_map_elt) please see the overview
>> + * of tracing_map data structures at the beginning of tracing_map.h.
>> + */
>> +
>> +/**
>> + * tracing_map_update_sum - Add a value to a tracing_map_elt's sum field
>> + * @elt: The tracing_map_elt
>> + * @i: The index of the given sum associated with the tracing_map_elt
>> + * @n: The value to add to the sum
>> + *
>> + * Add n to sum i associated with the specified tracing_map_elt
>> + * instance. The index i is the index returned by the call to
>> + * tracing_map_add_sum_field() when the tracing map was set up.
>> + */
>> +void tracing_map_update_sum(struct tracing_map_elt *elt, unsigned int i, u64 n)
>> +{
>> + atomic64_add(n, &elt->fields[i].sum);
>> +}
>> +
>> +/**
>> + * tracing_map_read_sum - Return the value of a tracing_map_elt's sum field
>> + * @elt: The tracing_map_elt
>> + * @i: The index of the given sum associated with the tracing_map_elt
>> + *
>> + * Retrieve the value of the sum i associated with the specified
>> + * tracing_map_elt instance. The index i is the index returned by the
>> + * call to tracing_map_add_sum_field() when the tracing map was set
>> + * up.
>> + *
>> + * Return: The sum associated with field i for elt.
>> + */
>> +u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i)
>> +{
>> + return (u64)atomic64_read(&elt->fields[i].sum);
>> +}
>> +
>> +int tracing_map_cmp_string(void *val_a, void *val_b)
>> +{
>> + char *a = val_a;
>> + char *b = val_b;
>> +
>> + return strcmp(a, b);
>> +}
>> +
>> +int tracing_map_cmp_none(void *val_a, void *val_b)
>> +{
>> + return 0;
>> +}
>> +
>> +static int tracing_map_cmp_atomic64(void *val_a, void *val_b)
>> +{
>> + u64 a = atomic64_read((atomic64_t *)val_a);
>> + u64 b = atomic64_read((atomic64_t *)val_b);
>> +
>> + return (a > b) ? 1 : ((a < b) ? -1 : 0);
>> +}
>> +
>> +#define DEFINE_TRACING_MAP_CMP_FN(type) \
>> +static int tracing_map_cmp_##type(void *val_a, void *val_b) \
>> +{ \
>> + type a = *(type *)val_a; \
>> + type b = *(type *)val_b; \
>> + \
>> + return (a > b) ? 1 : ((a < b) ? -1 : 0); \
>> +}
>> +
>> +DEFINE_TRACING_MAP_CMP_FN(s64);
>> +DEFINE_TRACING_MAP_CMP_FN(u64);
>> +DEFINE_TRACING_MAP_CMP_FN(s32);
>> +DEFINE_TRACING_MAP_CMP_FN(u32);
>> +DEFINE_TRACING_MAP_CMP_FN(s16);
>> +DEFINE_TRACING_MAP_CMP_FN(u16);
>> +DEFINE_TRACING_MAP_CMP_FN(s8);
>> +DEFINE_TRACING_MAP_CMP_FN(u8);
>> +
>> +tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size,
>> + int field_is_signed)
>> +{
>> + tracing_map_cmp_fn_t fn = tracing_map_cmp_none;
>> +
>> + switch (field_size) {
>> + case 8:
>> + if (field_is_signed)
>> + fn = tracing_map_cmp_s64;
>> + else
>> + fn = tracing_map_cmp_u64;
>> + break;
>> + case 4:
>> + if (field_is_signed)
>> + fn = tracing_map_cmp_s32;
>> + else
>> + fn = tracing_map_cmp_u32;
>> + break;
>> + case 2:
>> + if (field_is_signed)
>> + fn = tracing_map_cmp_s16;
>> + else
>> + fn = tracing_map_cmp_u16;
>> + break;
>> + case 1:
>> + if (field_is_signed)
>> + fn = tracing_map_cmp_s8;
>> + else
>> + fn = tracing_map_cmp_u8;
>> + break;
>> + }
>> +
>> + return fn;
>> +}
>> +
>> +static int tracing_map_add_field(struct tracing_map *map,
>> + tracing_map_cmp_fn_t cmp_fn)
>> +{
>> + int ret = -EINVAL;
>> +
>> + if (map->n_fields < TRACING_MAP_FIELDS_MAX) {
>> + ret = map->n_fields;
>> + map->fields[map->n_fields++].cmp_fn = cmp_fn;
>> + }
>> +
>> + return ret;
>> +}
>> +
>> +/**
>> + * tracing_map_add_sum_field - Add a field describing a tracing_map sum
>> + * @map: The tracing_map
>> + *
>> + * Add a sum field to the key and return the index identifying it in
>> + * the map and associated tracing_map_elts. This is the index used
>> + * for instance to update a sum for a particular tracing_map_elt using
>> + * tracing_map_update_sum() or reading it via tracing_map_read_sum().
>> + *
>> + * Return: The index identifying the field in the map and associated
>> + * tracing_map_elts.
>> + */
>> +int tracing_map_add_sum_field(struct tracing_map *map)
>> +{
>> + return tracing_map_add_field(map, tracing_map_cmp_atomic64);
>> +}
>> +
>> +/**
>> + * tracing_map_add_key_field - Add a field describing a tracing_map key
>> + * @map: The tracing_map
>> + * @offset: The offset within the key
>> + * @cmp_fn: The comparison function that will be used to sort on the key
>> + *
>> + * Let the map know there is a key and that if it's used as a sort key
>> + * to use cmp_fn.
>> + *
>> + * A key can be a subset of a compound key; for that purpose, the
>> + * offset param is used to describe where within the the compound key
>> + * the key referenced by this key field resides.
>> + *
>> + * Return: The index identifying the field in the map and associated
>> + * tracing_map_elts.
>> + */
>> +int tracing_map_add_key_field(struct tracing_map *map,
>> + unsigned int offset,
>> + tracing_map_cmp_fn_t cmp_fn)
>> +
>> +{
>> + int idx = tracing_map_add_field(map, cmp_fn);
>> +
>> + if (idx < 0)
>> + return idx;
>> +
>> + map->fields[idx].offset = offset;
>> +
>> + map->key_idx[map->n_keys++] = idx;
>> +
>> + return idx;
>> +}
>> +
>> +static void tracing_map_elt_clear(struct tracing_map_elt *elt)
>> +{
>> + unsigned i;
>> +
>> + for (i = 0; i < elt->map->n_fields; i++)
>> + if (elt->fields[i].cmp_fn == tracing_map_cmp_atomic64)
>> + atomic64_set(&elt->fields[i].sum, 0);
>> +
>> + if (elt->map->ops && elt->map->ops->elt_clear)
>> + elt->map->ops->elt_clear(elt);
>> +}
>> +
>> +static void tracing_map_elt_init_fields(struct tracing_map_elt *elt)
>> +{
>> + unsigned int i;
>> +
>> + tracing_map_elt_clear(elt);
>> +
>> + for (i = 0; i < elt->map->n_fields; i++) {
>> + elt->fields[i].cmp_fn = elt->map->fields[i].cmp_fn;
>> +
>> + if (elt->fields[i].cmp_fn != tracing_map_cmp_atomic64)
>> + elt->fields[i].offset = elt->map->fields[i].offset;
>> + }
>> +}
>> +
>> +static void tracing_map_elt_free(struct tracing_map_elt *elt)
>> +{
>> + if (!elt)
>> + return;
>> +
>> + if (elt->map->ops && elt->map->ops->elt_free)
>> + elt->map->ops->elt_free(elt);
>> + kfree(elt->fields);
>> + kfree(elt->key);
>> + kfree(elt);
>> +}
>> +
>> +static struct tracing_map_elt *tracing_map_elt_alloc(struct tracing_map *map)
>> +{
>> + struct tracing_map_elt *elt;
>> + int err = 0;
>> +
>> + elt = kzalloc(sizeof(*elt), GFP_KERNEL);
>> + if (!elt)
>> + return ERR_PTR(-ENOMEM);
>> +
>> + elt->map = map;
>> +
>> + elt->key = kzalloc(map->key_size, GFP_KERNEL);
>> + if (!elt->key) {
>> + err = -ENOMEM;
>> + goto free;
>> + }
>> +
>> + elt->fields = kcalloc(map->n_fields, sizeof(*elt->fields), GFP_KERNEL);
>> + if (!elt->fields) {
>> + err = -ENOMEM;
>> + goto free;
>> + }
>> +
>> + tracing_map_elt_init_fields(elt);
>> +
>> + if (map->ops && map->ops->elt_alloc) {
>> + err = map->ops->elt_alloc(elt);
>> + if (err)
>> + goto free;
>> + }
>> + return elt;
>> + free:
>> + tracing_map_elt_free(elt);
>> +
>> + return ERR_PTR(err);
>> +}
>> +
>> +static struct tracing_map_elt *get_free_elt(struct tracing_map *map)
>> +{
>> + struct tracing_map_elt *elt = NULL;
>> + int idx;
>> +
>> + idx = atomic_inc_return(&map->next_elt);
>> + if (idx < map->max_elts) {
>> + elt = map->elts[idx];
>> + if (map->ops && map->ops->elt_init)
>> + map->ops->elt_init(elt);
>> + }
>> +
>> + return elt;
>> +}
>> +
>> +static void tracing_map_free_elts(struct tracing_map *map)
>> +{
>> + unsigned int i;
>> +
>> + if (!map->elts)
>> + return;
>> +
>> + for (i = 0; i < map->max_elts; i++)
>> + tracing_map_elt_free(map->elts[i]);
>> +
>> + kfree(map->elts);
>> +}
>> +
>> +static int tracing_map_alloc_elts(struct tracing_map *map)
>> +{
>> + unsigned int i;
>> +
>> + map->elts = kcalloc(map->max_elts, sizeof(struct tracing_map_elt *),
>> + GFP_KERNEL);
>> + if (!map->elts)
>> + return -ENOMEM;
>> +
>> + for (i = 0; i < map->max_elts; i++) {
>> + map->elts[i] = tracing_map_elt_alloc(map);
>> + if (!map->elts[i]) {
>> + tracing_map_free_elts(map);
>> +
>> + return -ENOMEM;
>> + }
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static inline bool keys_match(void *key, void *test_key, unsigned key_size)
>> +{
>> + bool match = true;
>> +
>> + if (memcmp(key, test_key, key_size))
>> + match = false;
>> +
>> + return match;
>> +}
>> +
>> +/**
>> + * tracing_map_insert - Insert key and/or retrieve val from a tracing_map
>> + * @map: The tracing_map to insert into
>> + * @key: The key to insert
>> + *
>> + * Inserts a key into a tracing_map and creates and returns a new
>> + * tracing_map_elt for it, or if the key has already been inserted by
>> + * a previous call, returns the tracing_map_elt already associated
>> + * with it. When the map was created, the number of elements to be
>> + * allocated for the map was specified (internally maintained as
>> + * 'max_elts' in struct tracing_map), and that number of
>> + * tracing_map_elts was created by tracing_map_init(). This is the
>> + * pre-allocated pool of tracing_map_elts that tracing_map_insert()
>> + * will allocate from when adding new keys. Once that pool is
>> + * exhausted, tracing_map_insert() is useless and will return NULL to
>> + * signal that state.
>> + *
>> + * This is a lock-free tracing map insertion function implementing a
>> + * modified form of Cliff Click's basic insertion algorithm. It
>> + * requires the table size be a power of two. To prevent any
>> + * possibility of an infinite loop we always make the internal table
>> + * size double the size of the requested table size (max_elts * 2).
>> + * Likewise, we never reuse a slot or resize or delete elements - when
>> + * we've reached max_elts entries, we simply return NULL once we've
>> + * run out of entries. Readers can at any point in time traverse the
>> + * tracing map and safely access the key/val pairs.
>> + *
>> + * Return: the tracing_map_elt pointer val associated with the key.
>> + * If this was a newly inserted key, the val will be a newly allocated
>> + * and associated tracing_map_elt pointer val. If the key wasn't
>> + * found and the pool of tracing_map_elts has been exhausted, NULL is
>> + * returned and no further insertions will succeed.
>> + */
>> +struct tracing_map_elt *tracing_map_insert(struct tracing_map *map, void *key)
>> +{
>> + u32 idx, key_hash, test_key;
>> +
>> + key_hash = jhash(key, map->key_size, 0);
>> + idx = key_hash >> (32 - (map->map_bits + 1));
>> +
>> + while (1) {
>> + idx &= (map->map_size - 1);
>> + test_key = map->map[idx].key;
>> +
>> + if (test_key && test_key == key_hash && map->map[idx].val &&
>> + keys_match(key, map->map[idx].val->key, map->key_size))
>> + return map->map[idx].val;
>> +
>> + if (!test_key && !cmpxchg(&map->map[idx].key, 0, key_hash)) {
>> + struct tracing_map_elt *elt;
>> +
>> + elt = get_free_elt(map);
>> + if (!elt)
>> + break;
>> + memcpy(elt->key, key, map->key_size);
>> + map->map[idx].val = elt;
>> +
>> + return map->map[idx].val;
>> + }
>> + idx++;
>> + }
>> +
>> + return NULL;
>> +}
>> +
>> +/**
>> + * tracing_map_destroy - Destroy a tracing_map
>> + * @map: The tracing_map to destroy
>> + *
>> + * Frees a tracing_map along with its associated array of
>> + * tracing_map_elts.
>> + *
>> + * Callers should make sure there are no readers or writers actively
>> + * reading or inserting into the map before calling this.
>> + */
>> +void tracing_map_destroy(struct tracing_map *map)
>> +{
>> + if (!map)
>> + return;
>> +
>> + tracing_map_free_elts(map);
>> +
>> + kfree(map->map);
>> + kfree(map);
>> +}
>> +
>> +/**
>> + * tracing_map_clear - Clear a tracing_map
>> + * @map: The tracing_map to clear
>> + *
>> + * Resets the tracing map to a cleared or initial state. The
>> + * tracing_map_elts are all cleared, and the array of struct
>> + * tracing_map_entry is reset to an initialized state.
>> + *
>> + * Callers should make sure there are no writers actively inserting
>> + * into the map before calling this.
>> + */
>> +void tracing_map_clear(struct tracing_map *map)
>> +{
>> + unsigned int i, size;
>> +
>> + atomic_set(&map->next_elt, -1);
>> +
>> + size = map->map_size * sizeof(struct tracing_map_entry);
>> + memset(map->map, 0, size);
>> +
>> + for (i = 0; i < map->max_elts; i++)
>> + tracing_map_elt_clear(map->elts[i]);
>> +}
>> +
>> +static void set_sort_key(struct tracing_map *map,
>> + struct tracing_map_sort_key *sort_key)
>> +{
>> + map->sort_key = *sort_key;
>> +}
>> +
>> +/**
>> + * tracing_map_create - Create a lock-free map and element pool
>> + * @map_bits: The size of the map (2 ** map_bits)
>> + * @key_size: The size of the key for the map in bytes
>> + * @ops: Optional client-defined tracing_map_ops instance
>> + * @private_data: Client data associated with the map
>> + *
>> + * Creates and sets up a map to contain 2 ** map_bits number of
>> + * elements (internally maintained as 'max_elts' in struct
>> + * tracing_map). Before using, map fields should be added to the map
>> + * with tracing_map_add_sum_field() and tracing_map_add_key_field().
>> + * tracing_map_init() should then be called to allocate the array of
>> + * tracing_map_elts, in order to avoid allocating anything in the map
>> + * insertion path. The user-specified map size reflects the maximum
>> + * number of elements that can be contained in the table requested by
>> + * the user - internally we double that in order to keep the table
>> + * sparse and keep collisions manageable.
>> + *
>> + * A tracing_map is a special-purpose map designed to aggregate or
>> + * 'sum' one or more values associated with a specific object of type
>> + * tracing_map_elt, which is attached by the map to a given key.
>> + *
>> + * tracing_map_create() sets up the map itself, and provides
>> + * operations for inserting tracing_map_elts, but doesn't allocate the
>> + * tracing_map_elts themselves, or provide a means for describing the
>> + * keys or sums associated with the tracing_map_elts. All
>> + * tracing_map_elts for a given map have the same set of sums and
>> + * keys, which are defined by the client using the functions
>> + * tracing_map_add_key_field() and tracing_map_add_sum_field(). Once
>> + * the fields are defined, the pool of elements allocated for the map
>> + * can be created, which occurs when the client code calls
>> + * tracing_map_init().
>> + *
>> + * When tracing_map_init() returns, tracing_map_elt elements can be
>> + * inserted into the map using tracing_map_insert(). When called,
>> + * tracing_map_insert() grabs a free tracing_map_elt from the pool, or
>> + * finds an existing match in the map and in either case returns it.
>> + * The client can then use tracing_map_update_sum() and
>> + * tracing_map_read_sum() to update or read a given sum field for the
>> + * tracing_map_elt.
>> + *
>> + * The client can at any point retrieve and traverse the current set
>> + * of inserted tracing_map_elts in a tracing_map, via
>> + * tracing_map_sort_entries(). Sorting can be done on any field,
>> + * including keys.
>> + *
>> + * See tracing_map.h for a description of tracing_map_ops.
>> + *
>> + * Return: the tracing_map pointer if successful, ERR_PTR if not.
>> + */
>> +struct tracing_map *tracing_map_create(unsigned int map_bits,
>> + unsigned int key_size,
>> + struct tracing_map_ops *ops,
>> + void *private_data)
>> +{
>> + struct tracing_map *map;
>> + unsigned int i;
>> +
>> + if (map_bits < TRACING_MAP_BITS_MIN ||
>> + map_bits > TRACING_MAP_BITS_MAX)
>> + return ERR_PTR(-EINVAL);
>> +
>> + map = kzalloc(sizeof(*map), GFP_KERNEL);
>> + if (!map)
>> + return ERR_PTR(-ENOMEM);
>> +
>> + map->map_bits = map_bits;
>> + map->max_elts = (1 << map_bits);
>> + atomic_set(&map->next_elt, -1);
>> +
>> + map->map_size = (1 << (map_bits + 1));
>> + map->ops = ops;
>> +
>> + map->private_data = private_data;
>> +
>> + map->map = kcalloc(map->map_size, sizeof(struct tracing_map_entry),
>> + GFP_KERNEL);
>> + if (!map->map)
>> + goto free;
>> +
>> + map->key_size = key_size;
>> + for (i = 0; i < TRACING_MAP_KEYS_MAX; i++)
>> + map->key_idx[i] = -1;
>> + out:
>> + return map;
>> + free:
>> + tracing_map_destroy(map);
>> + map = ERR_PTR(-ENOMEM);
>> +
>> + goto out;
>> +}
>> +
>> +/**
>> + * tracing_map_init - Allocate and clear a map's tracing_map_elts
>> + * @map: The tracing_map to initialize
>> + *
>> + * Allocates a clears a pool of tracing_map_elts equal to the
>> + * user-specified size of 2 ** map_bits (internally maintained as
>> + * 'max_elts' in struct tracing_map). Before using, the map fields
>> + * should be added to the map with tracing_map_add_sum_field() and
>> + * tracing_map_add_key_field(). tracing_map_init() should then be
>> + * called to allocate the array of tracing_map_elts, in order to avoid
>> + * allocating anything in the map insertion path. The user-specified
>> + * map size reflects the max number of elements requested by the user
>> + * - internally we double that in order to keep the table sparse and
>> + * keep collisions manageable.
>> + *
>> + * See tracing_map.h for a description of tracing_map_ops.
>> + *
>> + * Return: the tracing_map pointer if successful, ERR_PTR if not.
>> + */
>> +int tracing_map_init(struct tracing_map *map)
>> +{
>> + int err;
>> +
>> + if (map->n_fields < 2)
>> + return -EINVAL; /* need at least 1 key and 1 val */
>> +
>> + err = tracing_map_alloc_elts(map);
>> + if (err)
>> + return err;
>> +
>> + tracing_map_clear(map);
>> +
>> + return err;
>> +}
>> +
>> +static int cmp_entries_dup(const struct tracing_map_sort_entry **a,
>> + const struct tracing_map_sort_entry **b)
>> +{
>> + int ret = 0;
>> +
>> + if (memcmp((*a)->key, (*b)->key, (*a)->elt->map->key_size))
>> + ret = 1;
>> +
>> + return ret;
>> +}
>> +
>> +static int cmp_entries_sum(const struct tracing_map_sort_entry **a,
>> + const struct tracing_map_sort_entry **b)
>> +{
>> + const struct tracing_map_elt *elt_a, *elt_b;
>> + struct tracing_map_sort_key *sort_key;
>> + struct tracing_map_field *field;
>> + tracing_map_cmp_fn_t cmp_fn;
>> + void *val_a, *val_b;
>> + int ret = 0;
>> +
>> + elt_a = (*a)->elt;
>> + elt_b = (*b)->elt;
>> +
>> + sort_key = &elt_a->map->sort_key;
>> +
>> + field = &elt_a->fields[sort_key->field_idx];
>> + cmp_fn = field->cmp_fn;
>> +
>> + val_a = &elt_a->fields[sort_key->field_idx].sum;
>> + val_b = &elt_b->fields[sort_key->field_idx].sum;
>> +
>> + ret = cmp_fn(val_a, val_b);
>> + if (sort_key->descending)
>> + ret = -ret;
>> +
>> + return ret;
>> +}
>> +
>> +static int cmp_entries_key(const struct tracing_map_sort_entry **a,
>> + const struct tracing_map_sort_entry **b)
>> +{
>> + const struct tracing_map_elt *elt_a, *elt_b;
>> + struct tracing_map_sort_key *sort_key;
>> + struct tracing_map_field *field;
>> + tracing_map_cmp_fn_t cmp_fn;
>> + void *val_a, *val_b;
>> + int ret = 0;
>> +
>> + elt_a = (*a)->elt;
>> + elt_b = (*b)->elt;
>> +
>> + sort_key = &elt_a->map->sort_key;
>> +
>> + field = &elt_a->fields[sort_key->field_idx];
>> +
>> + cmp_fn = field->cmp_fn;
>> +
>> + val_a = elt_a->key + field->offset;
>> + val_b = elt_b->key + field->offset;
>> +
>> + ret = cmp_fn(val_a, val_b);
>> + if (sort_key->descending)
>> + ret = -ret;
>> +
>> + return ret;
>> +}
>> +
>> +static void destroy_sort_entry(struct tracing_map_sort_entry *entry)
>> +{
>> + if (!entry)
>> + return;
>> +
>> + if (entry->elt_copied)
>> + tracing_map_elt_free(entry->elt);
>> +
>> + kfree(entry);
>> +}
>> +
>> +/**
>> + * tracing_map_destroy_entries - Destroy a tracing_map_sort_entries() array
>> + * @entries: The entries to destroy
>> + * @n_entries: The number of entries in the array
>> + *
>> + * Destroy the elements returned by a tracing_map_sort_entries() call.
>> + */
>> +void tracing_map_destroy_sort_entries(struct tracing_map_sort_entry **entries,
>> + unsigned int n_entries)
>> +{
>> + unsigned int i;
>> +
>> + for (i = 0; i < n_entries; i++)
>> + destroy_sort_entry(entries[i]);
>> +}
>> +
>> +static struct tracing_map_sort_entry *
>> +create_sort_entry(void *key, struct tracing_map_elt *elt)
>> +{
>> + struct tracing_map_sort_entry *sort_entry;
>> +
>> + sort_entry = kzalloc(sizeof(*sort_entry), GFP_KERNEL);
>> + if (!sort_entry)
>> + return NULL;
>> +
>> + sort_entry->key = key;
>> + sort_entry->elt = elt;
>> +
>> + return sort_entry;
>> +}
>> +
>> +static struct tracing_map_elt *copy_elt(struct tracing_map_elt *elt)
>> +{
>> + struct tracing_map_elt *dup_elt;
>> + unsigned int i;
>> +
>> + dup_elt = tracing_map_elt_alloc(elt->map);
>> + if (!dup_elt)
>> + return NULL;
>> +
>> + if (elt->map->ops && elt->map->ops->elt_copy)
>> + elt->map->ops->elt_copy(dup_elt, elt);
>> +
>> + dup_elt->private_data = elt->private_data;
>> + memcpy(dup_elt->key, elt->key, elt->map->key_size);
>> +
>> + for (i = 0; i < elt->map->n_fields; i++) {
>> + atomic64_set(&dup_elt->fields[i].sum,
>> + atomic64_read(&elt->fields[i].sum));
>> + dup_elt->fields[i].cmp_fn = elt->fields[i].cmp_fn;
>> + }
>> +
>> + return dup_elt;
>> +}
>> +
>> +static int merge_dup(struct tracing_map_sort_entry **sort_entries,
>> + unsigned int target, unsigned int dup)
>> +{
>> + struct tracing_map_elt *target_elt, *elt;
>> + bool first_dup = (target - dup) == 1;
>> + int i;
>> +
>> + if (first_dup) {
>> + elt = sort_entries[target]->elt;
>> + target_elt = copy_elt(elt);
>> + if (!target_elt)
>> + return -ENOMEM;
>> + sort_entries[target]->elt = target_elt;
>> + sort_entries[target]->elt_copied = true;
>> + } else
>> + target_elt = sort_entries[target]->elt;
>> +
>> + elt = sort_entries[dup]->elt;
>> +
>> + for (i = 0; i < elt->map->n_fields; i++)
>> + atomic64_add(atomic64_read(&elt->fields[i].sum),
>> + &target_elt->fields[i].sum);
>> +
>> + sort_entries[dup]->dup = true;
>> +
>> + return 0;
>> +}
>> +
>> +static int merge_dups(struct tracing_map_sort_entry **sort_entries,
>> + int n_entries, unsigned int key_size)
>> +{
>> + unsigned int dups = 0, total_dups = 0;
>> + int err, i, j;
>> + void *key;
>> +
>> + if (n_entries < 2)
>> + return total_dups;
>> +
>> + sort(sort_entries, n_entries, sizeof(struct tracing_map_sort_entry *),
>> + (int (*)(const void *, const void *))cmp_entries_dup, NULL);
>> +
>> + key = sort_entries[0]->key;
>> + for (i = 1; i < n_entries; i++) {
>> + if (!memcmp(sort_entries[i]->key, key, key_size)) {
>> + dups++; total_dups++;
>> + err = merge_dup(sort_entries, i - dups, i);
>> + if (err)
>> + return err;
>> + continue;
>> + }
>> + key = sort_entries[i]->key;
>> + dups = 0;
>> + }
>> +
>> + if (!total_dups)
>> + return total_dups;
>> +
>> + for (i = 0, j = 0; i < n_entries; i++) {
>> + if (!sort_entries[i]->dup) {
>> + sort_entries[j] = sort_entries[i];
>> + if (j++ != i)
>> + sort_entries[i] = NULL;
>> + } else {
>> + destroy_sort_entry(sort_entries[i]);
>> + sort_entries[i] = NULL;
>> + }
>> + }
>> +
>> + return total_dups;
>> +}
>> +
>> +static bool is_key(struct tracing_map *map, unsigned int field_idx)
>> +{
>> + unsigned int i;
>> +
>> + for (i = 0; i < map->n_keys; i++)
>> + if (map->key_idx[i] == field_idx)
>> + return true;
>> + return false;
>> +}
>> +
>> +static void sort_secondary(struct tracing_map *map,
>> + const struct tracing_map_sort_entry **entries,
>> + unsigned int n_entries,
>> + struct tracing_map_sort_key *primary_key,
>> + struct tracing_map_sort_key *secondary_key)
>> +{
>> + int (*primary_fn)(const struct tracing_map_sort_entry **,
>> + const struct tracing_map_sort_entry **);
>> + int (*secondary_fn)(const struct tracing_map_sort_entry **,
>> + const struct tracing_map_sort_entry **);
>> + unsigned i, start = 0, n_sub = 1;
>> +
>> + if (is_key(map, primary_key->field_idx))
>> + primary_fn = cmp_entries_key;
>> + else
>> + primary_fn = cmp_entries_sum;
>> +
>> + if (is_key(map, secondary_key->field_idx))
>> + secondary_fn = cmp_entries_key;
>> + else
>> + secondary_fn = cmp_entries_sum;
>> +
>> + for (i = 0; i < n_entries - 1; i++) {
>> + const struct tracing_map_sort_entry **a = &entries[i];
>> + const struct tracing_map_sort_entry **b = &entries[i + 1];
>> +
>> + if (primary_fn(a, b) == 0) {
>> + n_sub++;
>> + if (i < n_entries - 2)
>> + continue;
>> + }
>> +
>> + if (n_sub < 2) {
>> + start = i + 1;
>> + n_sub = 1;
>> + continue;
>> + }
>> +
>> + set_sort_key(map, secondary_key);
>> + sort(&entries[start], n_sub,
>> + sizeof(struct tracing_map_sort_entry *),
>> + (int (*)(const void *, const void *))secondary_fn, NULL);
>> + set_sort_key(map, primary_key);
>> +
>> + start = i + 1;
>> + n_sub = 1;
>> + }
>> +}
>> +
>> +/**
>> + * tracing_map_sort_entries - Sort the current set of tracing_map_elts in a map
>> + * @map: The tracing_map
>> + * @sort_key: The sort key to use for sorting
>> + * @sort_entries: outval: pointer to allocated and sorted array of entries
>> + *
>> + * tracing_map_sort_entries() sorts the current set of entries in the
>> + * map and returns the list of tracing_map_sort_entries containing
>> + * them to the client in the sort_entries param. The client can
>> + * access the struct tracing_map_elt element of interest directly as
>> + * the 'elt' field of a returned struct tracing_map_sort_entry object.
>> + *
>> + * The sort_key has only two fields: idx and descending. 'idx' refers
>> + * to the index of the field added via tracing_map_add_sum_field() or
>> + * tracing_map_add_key_field() when the tracing_map was initialized.
>> + * 'descending' is a flag that if set reverses the sort order, which
>> + * by default is ascending.
>> + *
>> + * The client should not hold on to the returned array but should use
>> + * it and call tracing_map_destroy_sort_entries() when done.
>> + *
>> + * Return: the number of sort_entries in the struct tracing_map_sort_entry
>> + * array, negative on error
>> + */
>> +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)
>> +{
>> + int (*cmp_entries_fn)(const struct tracing_map_sort_entry **,
>> + const struct tracing_map_sort_entry **);
>> + struct tracing_map_sort_entry *sort_entry, **entries;
>> + int i, n_entries, ret;
>> +
>> + entries = kcalloc(map->max_elts, sizeof(sort_entry), GFP_KERNEL);
>> + if (!entries)
>> + return -ENOMEM;
>> +
>> + for (i = 0, n_entries = 0; i < map->map_size; i++) {
>> + if (!map->map[i].key || !map->map[i].val)
>> + continue;
>> +
>> + entries[n_entries] = create_sort_entry(map->map[i].val->key,
>> + map->map[i].val);
>> + if (!entries[n_entries++]) {
>> + ret = -ENOMEM;
>> + goto free;
>> + }
>> + }
>> +
>> + if (n_entries == 0) {
>> + ret = 0;
>> + goto free;
>> + }
>> +
>> + if (n_entries == 1) {
>> + *sort_entries = entries;
>> + return 1;
>> + }
>> +
>> + ret = merge_dups(entries, n_entries, map->key_size);
>> + if (ret < 0)
>> + goto free;
>> + n_entries -= ret;
>> +
>> + if (is_key(map, sort_keys[0].field_idx))
>> + cmp_entries_fn = cmp_entries_key;
>> + else
>> + cmp_entries_fn = cmp_entries_sum;
>> +
>> + set_sort_key(map, &sort_keys[0]);
>> +
>> + sort(entries, n_entries, sizeof(struct tracing_map_sort_entry *),
>> + (int (*)(const void *, const void *))cmp_entries_fn, NULL);
>> +
>> + if (n_sort_keys > 1)
>> + sort_secondary(map,
>> + (const struct tracing_map_sort_entry **)entries,
>> + n_entries,
>> + &sort_keys[0],
>> + &sort_keys[1]);
>> +
>> + *sort_entries = entries;
>> +
>> + return n_entries;
>> + free:
>> + tracing_map_destroy_sort_entries(entries, n_entries);
>> +
>> + return ret;
>> +}
>> diff --git a/kernel/trace/tracing_map.h b/kernel/trace/tracing_map.h
>> new file mode 100644
>> index 0000000..2e63c5c
>> --- /dev/null
>> +++ b/kernel/trace/tracing_map.h
>> @@ -0,0 +1,258 @@
>> +#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 {
>> + unsigned int key_size;
>> + unsigned int map_bits;
>> + unsigned int map_size;
>> + unsigned int max_elts;
>> + atomic_t next_elt;
>> + struct tracing_map_elt **elts;
>> + struct tracing_map_entry *map;
>> + 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;
>> +};
>> +
>> +/**
>> + * 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,
>> + 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 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 */
>> --
>> 1.9.3
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>> the body of a message to majordomo@...r.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>> Please read the FAQ at http://www.tux.org/lkml/
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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