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plugins/cache: supported multicore cache modelling 

Multicore L1 cache modelling is introduced and is supported for both
full system emulation and linux-user.

For full-system emulation, L1 icache and dcache are maintained for each
available core, since this information is exposed to the plugin through
`qemu_plugin_n_vcpus()`.

For linux-user, a static number of cores is assumed (default 1 core, and
can be provided as a plugin argument `cores=N`). Every memory access
goes through one of these caches, this approach is taken as it's
somewhat akin to what happens on real setup, where a program that
dispatches more threads than the available cores, they'll thrash
each other

Signed-off-by: Mahmoud Mandour <ma.mandourr@gmail.com>
Message-Id: <20210803151301.123581-2-ma.mandourr@gmail.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
This commit is contained in:
Mahmoud Mandour 2021-08-03 17:13:00 +02:00 committed by Alex Bennée
parent b906acace2
commit c79a2116af
1 changed files with 131 additions and 43 deletions
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174
contrib/plugins/cache.c
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@ -17,18 +17,12 @@ static enum qemu_plugin_mem_rw rw = QEMU_PLUGIN_MEM_RW;
static GHashTable *miss_ht;
static GMutex mtx;
static GMutex hashtable_lock;
static GRand *rng;
static int limit;
static bool sys;
static uint64_t dmem_accesses;
static uint64_t dmisses;
static uint64_t imem_accesses;
static uint64_t imisses;
enum EvictionPolicy {
LRU,
FIFO,
@ -80,6 +74,8 @@ typedef struct {
int blksize_shift;
uint64_t set_mask;
uint64_t tag_mask;
uint64_t accesses;
uint64_t misses;
} Cache;
typedef struct {
@ -96,7 +92,16 @@ void (*update_miss)(Cache *cache, int set, int blk);
void (*metadata_init)(Cache *cache);
void (*metadata_destroy)(Cache *cache);
Cache *dcache, *icache;
static int cores;
static Cache **dcaches, **icaches;
static GMutex *dcache_locks;
static GMutex *icache_locks;
static uint64_t all_dmem_accesses;
static uint64_t all_imem_accesses;
static uint64_t all_imisses;
static uint64_t all_dmisses;
static int pow_of_two(int num)
{
@ -233,20 +238,24 @@ static bool bad_cache_params(int blksize, int assoc, int cachesize)
static Cache *cache_init(int blksize, int assoc, int cachesize)
{
if (bad_cache_params(blksize, assoc, cachesize)) {
return NULL;
}
Cache *cache;
int i;
uint64_t blk_mask;
/*
* This function shall not be called directly, and hence expects suitable
* parameters.
*/
g_assert(!bad_cache_params(blksize, assoc, cachesize));
cache = g_new(Cache, 1);
cache->assoc = assoc;
cache->cachesize = cachesize;
cache->num_sets = cachesize / (blksize * assoc);
cache->sets = g_new(CacheSet, cache->num_sets);
cache->blksize_shift = pow_of_two(blksize);
cache->accesses = 0;
cache->misses = 0;
for (i = 0; i < cache->num_sets; i++) {
cache->sets[i].blocks = g_new0(CacheBlock, assoc);
@ -263,6 +272,24 @@ static Cache *cache_init(int blksize, int assoc, int cachesize)
return cache;
}
static Cache **caches_init(int blksize, int assoc, int cachesize)
{
Cache **caches;
int i;
if (bad_cache_params(blksize, assoc, cachesize)) {
return NULL;
}
caches = g_new(Cache *, cores);
for (i = 0; i < cores; i++) {
caches[i] = cache_init(blksize, assoc, cachesize);
}
return caches;
}
static int get_invalid_block(Cache *cache, uint64_t set)
{
int i;
@ -353,6 +380,7 @@ static void vcpu_mem_access(unsigned int vcpu_index, qemu_plugin_meminfo_t info,
{
uint64_t effective_addr;
struct qemu_plugin_hwaddr *hwaddr;
int cache_idx;
InsnData *insn;
hwaddr = qemu_plugin_get_hwaddr(info, vaddr);
@ -361,32 +389,35 @@ static void vcpu_mem_access(unsigned int vcpu_index, qemu_plugin_meminfo_t info,
}
effective_addr = hwaddr ? qemu_plugin_hwaddr_phys_addr(hwaddr) : vaddr;
cache_idx = vcpu_index % cores;
g_mutex_lock(&mtx);
if (!access_cache(dcache, effective_addr)) {
g_mutex_lock(&dcache_locks[cache_idx]);
if (!access_cache(dcaches[cache_idx], effective_addr)) {
insn = (InsnData *) userdata;
insn->dmisses++;
dmisses++;
__atomic_fetch_add(&insn->dmisses, 1, __ATOMIC_SEQ_CST);
dcaches[cache_idx]->misses++;
}
dmem_accesses++;
g_mutex_unlock(&mtx);
dcaches[cache_idx]->accesses++;
g_mutex_unlock(&dcache_locks[cache_idx]);
}
static void vcpu_insn_exec(unsigned int vcpu_index, void *userdata)
{
uint64_t insn_addr;
InsnData *insn;
int cache_idx;
g_mutex_lock(&mtx);
insn_addr = ((InsnData *) userdata)->addr;
if (!access_cache(icache, insn_addr)) {
cache_idx = vcpu_index % cores;
g_mutex_lock(&icache_locks[cache_idx]);
if (!access_cache(icaches[cache_idx], insn_addr)) {
insn = (InsnData *) userdata;
insn->imisses++;
imisses++;
__atomic_fetch_add(&insn->imisses, 1, __ATOMIC_SEQ_CST);
icaches[cache_idx]->misses++;
}
imem_accesses++;
g_mutex_unlock(&mtx);
icaches[cache_idx]->accesses++;
g_mutex_unlock(&icache_locks[cache_idx]);
}
static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
@ -411,7 +442,7 @@ static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
* new entries for those instructions. Instead, we fetch the same
* entry from the hash table and register it for the callback again.
*/
g_mutex_lock(&mtx);
g_mutex_lock(&hashtable_lock);
data = g_hash_table_lookup(miss_ht, GUINT_TO_POINTER(effective_addr));
if (data == NULL) {
data = g_new0(InsnData, 1);
@ -421,7 +452,7 @@ static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
g_hash_table_insert(miss_ht, GUINT_TO_POINTER(effective_addr),
(gpointer) data);
}
g_mutex_unlock(&mtx);
g_mutex_unlock(&hashtable_lock);
qemu_plugin_register_vcpu_mem_cb(insn, vcpu_mem_access,
QEMU_PLUGIN_CB_NO_REGS,
@ -453,6 +484,15 @@ static void cache_free(Cache *cache)
g_free(cache);
}
static void caches_free(Cache **caches)
{
int i;
for (i = 0; i < cores; i++) {
cache_free(caches[i]);
}
}
static int dcmp(gconstpointer a, gconstpointer b)
{
InsnData *insn_a = (InsnData *) a;
@ -461,6 +501,37 @@ static int dcmp(gconstpointer a, gconstpointer b)
return insn_a->dmisses < insn_b->dmisses ? 1 : -1;
}
static void append_stats_line(GString *line, uint64_t daccess, uint64_t dmisses,
uint64_t iaccess, uint64_t imisses)
{
double dmiss_rate, imiss_rate;
dmiss_rate = ((double) dmisses) / (daccess) * 100.0;
imiss_rate = ((double) imisses) / (iaccess) * 100.0;
g_string_append_printf(line, "%-14lu %-12lu %9.4lf%% %-14lu %-12lu"
" %9.4lf%%\n",
daccess,
dmisses,
daccess ? dmiss_rate : 0.0,
iaccess,
imisses,
iaccess ? imiss_rate : 0.0);
}
static void sum_stats(void)
{
int i;
g_assert(cores > 1);
for (i = 0; i < cores; i++) {
all_imisses += icaches[i]->misses;
all_dmisses += dcaches[i]->misses;
all_imem_accesses += icaches[i]->accesses;
all_dmem_accesses += dcaches[i]->accesses;
}
}
static int icmp(gconstpointer a, gconstpointer b)
{
InsnData *insn_a = (InsnData *) a;
@ -471,19 +542,29 @@ static int icmp(gconstpointer a, gconstpointer b)
static void log_stats(void)
{
g_autoptr(GString) rep = g_string_new("");
g_string_append_printf(rep,
"Data accesses: %lu, Misses: %lu\nMiss rate: %lf%%\n\n",
dmem_accesses,
dmisses,
((double) dmisses / (double) dmem_accesses) * 100.0);
int i;
Cache *icache, *dcache;
g_string_append_printf(rep,
"Instruction accesses: %lu, Misses: %lu\nMiss rate: %lf%%\n\n",
imem_accesses,
imisses,
((double) imisses / (double) imem_accesses) * 100.0);
g_autoptr(GString) rep = g_string_new("core #, data accesses, data misses,"
" dmiss rate, insn accesses,"
" insn misses, imiss rate\n");
for (i = 0; i < cores; i++) {
g_string_append_printf(rep, "%-8d", i);
dcache = dcaches[i];
icache = icaches[i];
append_stats_line(rep, dcache->accesses, dcache->misses,
icache->accesses, icache->misses);
}
if (cores > 1) {
sum_stats();
g_string_append_printf(rep, "%-8s", "sum");
append_stats_line(rep, all_dmem_accesses, all_dmisses,
all_imem_accesses, all_imisses);
}
g_string_append(rep, "\n");
qemu_plugin_outs(rep->str);
}
@ -530,8 +611,8 @@ static void plugin_exit(qemu_plugin_id_t id, void *p)
log_stats();
log_top_insns();
cache_free(dcache);
cache_free(icache);
caches_free(dcaches);
caches_free(icaches);
g_hash_table_destroy(miss_ht);
}
@ -579,6 +660,8 @@ int qemu_plugin_install(qemu_plugin_id_t id, const qemu_info_t *info,
policy = LRU;
cores = sys ? qemu_plugin_n_vcpus() : 1;
for (i = 0; i < argc; i++) {
char *opt = argv[i];
if (g_str_has_prefix(opt, "iblksize=")) {
@ -595,6 +678,8 @@ 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, "cores=")) {
cores = 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) {
@ -615,22 +700,25 @@ int qemu_plugin_install(qemu_plugin_id_t id, const qemu_info_t *info,
policy_init();
dcache = cache_init(dblksize, dassoc, dcachesize);
if (!dcache) {
dcaches = caches_init(dblksize, dassoc, dcachesize);
if (!dcaches) {
const char *err = cache_config_error(dblksize, dassoc, dcachesize);
fprintf(stderr, "dcache cannot be constructed from given parameters\n");
fprintf(stderr, "%s\n", err);
return -1;
}
icache = cache_init(iblksize, iassoc, icachesize);
if (!icache) {
icaches = caches_init(iblksize, iassoc, icachesize);
if (!icaches) {
const char *err = cache_config_error(iblksize, iassoc, icachesize);
fprintf(stderr, "icache cannot be constructed from given parameters\n");
fprintf(stderr, "%s\n", err);
return -1;
}
dcache_locks = g_new0(GMutex, cores);
icache_locks = g_new0(GMutex, cores);
qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans);
qemu_plugin_register_atexit_cb(id, plugin_exit, NULL);