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[PATCH 4/6] plugins/cache: Supported multicore cache modelling
From: |
Mahmoud Mandour |
Subject: |
[PATCH 4/6] plugins/cache: Supported multicore cache modelling |
Date: |
Wed, 14 Jul 2021 19:21:50 +0200 |
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>
---
contrib/plugins/cache.c | 156 ++++++++++++++++++++++++++++++----------
1 file changed, 117 insertions(+), 39 deletions(-)
diff --git a/contrib/plugins/cache.c b/contrib/plugins/cache.c
index a452aba01c..60f7be208b 100644
--- a/contrib/plugins/cache.c
+++ b/contrib/plugins/cache.c
@@ -23,11 +23,6 @@ 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,
@@ -90,13 +85,22 @@ typedef struct {
uint64_t imisses;
} InsnData;
+typedef struct {
+ uint64_t dmem_accesses;
+ uint64_t dmisses;
+ uint64_t imem_accesses;
+ uint64_t imisses;
+} CoreStats;
+
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 cores;
+CoreStats *stats;
+Cache **dcaches, **icaches;
static int pow_of_two(int num)
{
@@ -233,10 +237,6 @@ 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;
@@ -263,6 +263,24 @@ 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 +371,7 @@ 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);
@@ -363,17 +382,24 @@ static void vcpu_mem_access(unsigned int vcpu_index,
qemu_plugin_meminfo_t info,
effective_addr = hwaddr ? qemu_plugin_hwaddr_phys_addr(hwaddr) : vaddr;
g_mutex_lock(&mtx);
- if (dcache == NULL) {
+ cache_idx = vcpu_index % cores;
+ if (dcaches[cache_idx] == NULL) {
g_mutex_unlock(&mtx);
return;
}
- if (!access_cache(dcache, effective_addr)) {
+ if (!access_cache(dcaches[cache_idx], effective_addr)) {
insn = (InsnData *) userdata;
insn->dmisses++;
- dmisses++;
+ if (cores > 1) {
+ stats[cores].dmisses++;
+ }
+ stats[cache_idx].dmisses++;
+ }
+ if (cores > 1) {
+ stats[cores].dmem_accesses++;
}
- dmem_accesses++;
+ stats[cache_idx].dmem_accesses++;
g_mutex_unlock(&mtx);
}
@@ -381,21 +407,29 @@ static void vcpu_insn_exec(unsigned int vcpu_index, void
*userdata)
{
uint64_t insn_addr;
InsnData *insn;
+ uint64_t cache_idx;
g_mutex_lock(&mtx);
insn_addr = ((InsnData *) userdata)->addr;
- if (icache == NULL) {
+ cache_idx = vcpu_index % cores;
+ if (icaches[cache_idx] == NULL) {
g_mutex_unlock(&mtx);
return;
}
- if (!access_cache(icache, insn_addr)) {
+ if (!access_cache(icaches[cache_idx], insn_addr)) {
insn = (InsnData *) userdata;
insn->imisses++;
- imisses++;
+ if (cores > 1) {
+ stats[cores].imisses++;
+ }
+ stats[cache_idx].imisses++;
}
- imem_accesses++;
+ if (cores > 1) {
+ stats[cores].imem_accesses++;
+ }
+ stats[cache_idx].imem_accesses++;
g_mutex_unlock(&mtx);
}
@@ -475,6 +509,22 @@ static void cache_free(Cache *cache)
g_free(cache);
}
+/*
+ * caches_free(): free an array of Cache structs.
+ * @caches: caches to free
+ *
+ * Calling cache_free for each cache in @caches, and then NULL-ify them so that
+ * we mark them as freed, other async callbacks can check to see whether a
cache
+ * is freed already or not by checking against NULL.
+ */
+static void caches_free(Cache **caches)
+{
+ for (int i = 0; i < cores; i++) {
+ cache_free(caches[i]);
+ caches[i] = NULL;
+ }
+}
+
static int dcmp(gconstpointer a, gconstpointer b)
{
InsnData *insn_a = (InsnData *) a;
@@ -493,19 +543,38 @@ static int icmp(gconstpointer a, gconstpointer b)
static void log_stats()
{
- 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);
-
- 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);
+ int i, iters;
+ CoreStats cs;
+ double dmiss_rate, imiss_rate;
+
+ g_autoptr(GString) rep = g_string_new("core #, data accesses, data misses,"
+ " dmiss rate, insn accesses,"
+ " insn misses, imiss rate\n");
+
+ /* Only iterate and print a sum row if cores > 1 */
+ iters = cores == 1 ? 1 : cores + 1;
+ for (i = 0; i < iters; i++) {
+ cs = stats[i];
+ dmiss_rate = ((double) cs.dmisses) / (cs.dmem_accesses) * 100.0;
+ imiss_rate = ((double) cs.imisses) / (cs.imem_accesses) * 100.0;
+
+ if (i == cores) {
+ g_string_append_printf(rep, "%-8s", "sum");
+ } else {
+ g_string_append_printf(rep, "%-8d", i);
+ }
+
+ g_string_append_printf(rep, "%-14lu %-12lu %9.4lf%% %-14lu %-12lu"
+ " %9.4lf%%\n",
+ cs.dmem_accesses,
+ cs.dmisses,
+ cs.dmem_accesses ? dmiss_rate : 0.0,
+ cs.imem_accesses,
+ cs.imisses,
+ cs.imem_accesses ? imiss_rate : 0.0);
+ }
+ g_string_append(rep, "\n");
qemu_plugin_outs(rep->str);
}
@@ -553,15 +622,14 @@ static void plugin_exit(qemu_plugin_id_t id, void *p)
log_stats();
log_top_insns();
- cache_free(dcache);
- dcache = NULL;
-
- cache_free(icache);
- icache = NULL;
+ caches_free(dcaches);
+ caches_free(icaches);
g_hash_table_destroy(miss_ht);
miss_ht = NULL;
+ g_free(stats);
+
g_mutex_unlock(&mtx);
}
@@ -608,6 +676,8 @@ 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=")) {
@@ -624,6 +694,8 @@ 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) {
@@ -644,22 +716,28 @@ 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;
}
+ /*
+ * plus one to save the sum in. If only one core is used then no need to
+ * get an auxiliary struct.
+ */
+ stats = g_new0(CoreStats, cores == 1 ? 1 : cores + 1);
+
qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans);
qemu_plugin_register_atexit_cb(id, plugin_exit, NULL);
--
2.25.1
[PATCH 5/6] docs/devel/tcg-plugins: added cores arg to cache plugin, Mahmoud Mandour, 2021/07/14
[PATCH 4/6] plugins/cache: Supported multicore cache modelling,
Mahmoud Mandour <=
[PATCH 2/6] plugins/cache: limited the scope of a mutex lock, Mahmoud Mandour, 2021/07/14
[PATCH 6/6] plugins/cache: Fixed "function decl. is not a prototype" warnings, Mahmoud Mandour, 2021/07/14
Re: [PATCH 0/6] plugins/cache: multicore cache emulation and minor, Alex Bennée, 2021/07/20