diff options
| -rw-r--r-- | contrib/plugins/cache.c | 203 |
1 files changed, 190 insertions, 13 deletions
diff --git a/contrib/plugins/cache.c b/contrib/plugins/cache.c index b550ef31b0..bf0d2f6097 100644 --- a/contrib/plugins/cache.c +++ b/contrib/plugins/cache.c @@ -29,6 +29,14 @@ static uint64_t dmisses; static uint64_t imem_accesses; static uint64_t imisses; +enum EvictionPolicy { + LRU, + FIFO, + RAND, +}; + +enum EvictionPolicy policy; + /* * A CacheSet is a set of cache blocks. A memory block that maps to a set can be * put in any of the blocks inside the set. The number of block per set is @@ -48,6 +56,8 @@ static uint64_t imisses; * The set number is used to identify the set in which the block may exist. * The tag is compared against all the tags of a set to search for a match. If a * match is found, then the access is a hit. + * + * The CacheSet also contains bookkeaping information about eviction details. */ typedef struct { @@ -57,6 +67,9 @@ typedef struct { typedef struct { CacheBlock *blocks; + uint64_t *lru_priorities; + uint64_t lru_gen_counter; + GQueue *fifo_queue; } CacheSet; typedef struct { @@ -77,6 +90,12 @@ typedef struct { uint64_t imisses; } InsnData; +void (*update_hit)(Cache *cache, int set, int blk); +void (*update_miss)(Cache *cache, int set, int blk); + +void (*metadata_init)(Cache *cache); +void (*metadata_destroy)(Cache *cache); + Cache *dcache, *icache; static int pow_of_two(int num) @@ -89,6 +108,103 @@ static int pow_of_two(int num) return ret; } +/* + * LRU evection policy: For each set, a generation counter is maintained + * alongside a priority array. + * + * On each set access, the generation counter is incremented. + * + * On a cache hit: The hit-block is assigned the current generation counter, + * indicating that it is the most recently used block. + * + * On a cache miss: The block with the least priority is searched and replaced + * with the newly-cached block, of which the priority is set to the current + * generation number. + */ + +static void lru_priorities_init(Cache *cache) +{ + int i; + + for (i = 0; i < cache->num_sets; i++) { + cache->sets[i].lru_priorities = g_new0(uint64_t, cache->assoc); + cache->sets[i].lru_gen_counter = 0; + } +} + +static void lru_update_blk(Cache *cache, int set_idx, int blk_idx) +{ + CacheSet *set = &cache->sets[set_idx]; + set->lru_priorities[blk_idx] = cache->sets[set_idx].lru_gen_counter; + set->lru_gen_counter++; +} + +static int lru_get_lru_block(Cache *cache, int set_idx) +{ + int i, min_idx, min_priority; + + min_priority = cache->sets[set_idx].lru_priorities[0]; + min_idx = 0; + + for (i = 1; i < cache->assoc; i++) { + if (cache->sets[set_idx].lru_priorities[i] < min_priority) { + min_priority = cache->sets[set_idx].lru_priorities[i]; + min_idx = i; + } + } + return min_idx; +} + +static void lru_priorities_destroy(Cache *cache) +{ + int i; + + for (i = 0; i < cache->num_sets; i++) { + g_free(cache->sets[i].lru_priorities); + } +} + +/* + * FIFO eviction policy: a FIFO queue is maintained for each CacheSet that + * stores accesses to the cache. + * + * On a compulsory miss: The block index is enqueued to the fifo_queue to + * indicate that it's the latest cached block. + * + * On a conflict miss: The first-in block is removed from the cache and the new + * block is put in its place and enqueued to the FIFO queue. + */ + +static void fifo_init(Cache *cache) +{ + int i; + + for (i = 0; i < cache->num_sets; i++) { + cache->sets[i].fifo_queue = g_queue_new(); + } +} + +static int fifo_get_first_block(Cache *cache, int set) +{ + GQueue *q = cache->sets[set].fifo_queue; + return GPOINTER_TO_INT(g_queue_pop_tail(q)); +} + +static void fifo_update_on_miss(Cache *cache, int set, int blk_idx) +{ + GQueue *q = cache->sets[set].fifo_queue; + g_queue_push_head(q, GINT_TO_POINTER(blk_idx)); +} + +static void fifo_destroy(Cache *cache) +{ + int i; + + for (i = 0; i < cache->assoc; i++) { + g_queue_free(cache->sets[i].fifo_queue); + } +} + static inline uint64_t extract_tag(Cache *cache, uint64_t addr) { return addr & cache->tag_mask; @@ -139,6 +255,11 @@ static Cache *cache_init(int blksize, int assoc, int cachesize) blk_mask = blksize - 1; cache->set_mask = ((cache->num_sets - 1) << cache->blksize_shift); cache->tag_mask = ~(cache->set_mask | blk_mask); + + if (metadata_init) { + metadata_init(cache); + } + return cache; } @@ -155,12 +276,21 @@ static int get_invalid_block(Cache *cache, uint64_t set) return -1; } -static int get_replaced_block(Cache *cache) +static int get_replaced_block(Cache *cache, int set) { - return g_rand_int_range(rng, 0, cache->assoc); + switch (policy) { + case RAND: + return g_rand_int_range(rng, 0, cache->assoc); + case LRU: + return lru_get_lru_block(cache, set); + case FIFO: + return fifo_get_first_block(cache, set); + default: + g_assert_not_reached(); + } } -static bool in_cache(Cache *cache, uint64_t addr) +static int in_cache(Cache *cache, uint64_t addr) { int i; uint64_t tag, set; @@ -171,11 +301,11 @@ static bool in_cache(Cache *cache, uint64_t addr) for (i = 0; i < cache->assoc; i++) { if (cache->sets[set].blocks[i].tag == tag && cache->sets[set].blocks[i].valid) { - return true; + return i; } } - return false; + return -1; } /** @@ -188,20 +318,28 @@ static bool in_cache(Cache *cache, uint64_t addr) */ static bool access_cache(Cache *cache, uint64_t addr) { + int hit_blk, replaced_blk; uint64_t tag, set; - int replaced_blk; - - if (in_cache(cache, addr)) { - return true; - } tag = extract_tag(cache, addr); set = extract_set(cache, addr); + hit_blk = in_cache(cache, addr); + if (hit_blk != -1) { + if (update_hit) { + update_hit(cache, set, hit_blk); + } + return true; + } + replaced_blk = get_invalid_block(cache, set); if (replaced_blk == -1) { - replaced_blk = get_replaced_block(cache); + replaced_blk = get_replaced_block(cache, set); + } + + if (update_miss) { + update_miss(cache, set, replaced_blk); } cache->sets[set].blocks[replaced_blk].tag = tag; @@ -308,6 +446,10 @@ static void cache_free(Cache *cache) g_free(cache->sets[i].blocks); } + if (metadata_destroy) { + metadata_destroy(cache); + } + g_free(cache->sets); g_free(cache); } @@ -395,6 +537,28 @@ static void plugin_exit(qemu_plugin_id_t id, void *p) g_hash_table_destroy(miss_ht); } +static void policy_init() +{ + switch (policy) { + case LRU: + update_hit = lru_update_blk; + update_miss = lru_update_blk; + metadata_init = lru_priorities_init; + metadata_destroy = lru_priorities_destroy; + break; + case FIFO: + update_miss = fifo_update_on_miss; + metadata_init = fifo_init; + metadata_destroy = fifo_destroy; + break; + case RAND: + rng = g_rand_new(); + break; + default: + g_assert_not_reached(); + } +} + QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id, const qemu_info_t *info, int argc, char **argv) @@ -414,6 +578,7 @@ int qemu_plugin_install(qemu_plugin_id_t id, const qemu_info_t *info, iblksize = 64; icachesize = iblksize * iassoc * 32; + policy = LRU; for (i = 0; i < argc; i++) { char *opt = argv[i]; @@ -431,12 +596,26 @@ int qemu_plugin_install(qemu_plugin_id_t id, const qemu_info_t *info, dcachesize = g_ascii_strtoll(opt + 11, NULL, 10); } else if (g_str_has_prefix(opt, "limit=")) { limit = g_ascii_strtoll(opt + 6, NULL, 10); + } else if (g_str_has_prefix(opt, "evict=")) { + gchar *p = opt + 6; + if (g_strcmp0(p, "rand") == 0) { + policy = RAND; + } else if (g_strcmp0(p, "lru") == 0) { + policy = LRU; + } else if (g_strcmp0(p, "fifo") == 0) { + policy = FIFO; + } else { + fprintf(stderr, "invalid eviction policy: %s\n", opt); + return -1; + } } else { fprintf(stderr, "option parsing failed: %s\n", opt); return -1; } } + policy_init(); + dcache = cache_init(dblksize, dassoc, dcachesize); if (!dcache) { const char *err = cache_config_error(dblksize, dassoc, dcachesize); @@ -453,8 +632,6 @@ int qemu_plugin_install(qemu_plugin_id_t id, const qemu_info_t *info, return -1; } - rng = g_rand_new(); - qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans); qemu_plugin_register_atexit_cb(id, plugin_exit, NULL); |