[PATCH V2 14/22] perf itrace: Add a hashtable for caching decoded instructions

Adrian Hunter
2014-11-20T13:29:50Z

Decoding Instruction Trace data may involve walking object
code. Rather than repetitively decoding the same instructions,
a cache can be used to cache the results.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
tools/perf/util/itrace.c | 123 +++++++++++++++++++++++++++++++++++++++++++++++
tools/perf/util/itrace.h | 14 ++++++
2 files changed, 137 insertions(+)

diff --git a/tools/perf/util/itrace.c b/tools/perf/util/itrace.c
index eb43a7f..fd67a9a 100644
--- a/tools/perf/util/itrace.c
+++ b/tools/perf/util/itrace.c
@@ -37,6 +37,8 @@
#include "thread_map.h"
#include "itrace.h"

+#include <linux/hash.h>
+
#include "event.h"
#include "session.h"
#include "debug.h"
@@ -916,3 +918,124 @@ int itrace_mmap__read(struct itrace_mmap *mm, struct itrace_record *itr,

return 1;
}
+
+/**
+ * struct itrace_cache - hash table to cache decoded instruction blocks
+ * @hashtable: the hashtable
+ * @sz: hashtable size (number of hlists)
+ * @entry_size: size of an entry
+ * @limit: limit the number of entries to this maximum, when reached the cache
+ * is dropped and caching begins again with an empty cache
+ * @cnt: current number of entries
+ * @bits: hashtable size (@sz = 2^@bits)
+ */
+struct itrace_cache {
+ struct hlist_head *hashtable;
+ size_t sz;
+ size_t entry_size;
+ size_t limit;
+ size_t cnt;
+ unsigned int bits;
+};
+
+struct itrace_cache *itrace_cache__new(unsigned int bits, size_t entry_size,
+ unsigned int limit_percent)
+{
+ struct itrace_cache *c;
+ struct hlist_head *ht;
+ size_t sz, i;
+
+ c = zalloc(sizeof(struct itrace_cache));
+ if (!c)
+ return NULL;
+
+ sz = 1UL << bits;
+
+ ht = calloc(sz, sizeof(struct hlist_head));
+ if (!ht)
+ goto out_free;
+
+ for (i = 0; i < sz; i++)
+ INIT_HLIST_HEAD(&ht[i]);
+
+ c->hashtable = ht;
+ c->sz = sz;
+ c->entry_size = entry_size;
+ c->limit = (c->sz * limit_percent) / 100;
+ c->bits = bits;
+
+ return c;
+
+out_free:
+ free(c);
+ return NULL;
+}
+
+static void itrace_cache__drop(struct itrace_cache *c)
+{
+ struct itrace_cache_entry *entry;
+ struct hlist_node *tmp;
+ size_t i;
+
+ if (!c)
+ return;
+
+ for (i = 0; i < c->sz; i++) {
+ hlist_for_each_entry_safe(entry, tmp, &c->hashtable[i], hash) {
+ hlist_del(&entry->hash);
+ itrace_cache__free_entry(c, entry);
+ }
+ }
+
+ c->cnt = 0;
+}
+
+void itrace_cache__free(struct itrace_cache *c)
+{
+ if (!c)
+ return;
+
+ itrace_cache__drop(c);
+ free(c->hashtable);
+ free(c);
+}
+
+void *itrace_cache__alloc_entry(struct itrace_cache *c)
+{
+ return malloc(c->entry_size);
+}
+
+void itrace_cache__free_entry(struct itrace_cache *c __maybe_unused,
+ void *entry)
+{
+ free(entry);
+}
+
+int itrace_cache__add(struct itrace_cache *c, u32 key,
+ struct itrace_cache_entry *entry)
+{
+ if (c->limit && ++c->cnt > c->limit)
+ itrace_cache__drop(c);
+
+ entry->key = key;
+ hlist_add_head(&entry->hash, &c->hashtable[hash_32(key, c->bits)]);
+
+ return 0;
+}
+
+void *itrace_cache__lookup(struct itrace_cache *c, u32 key)
+{
+ struct itrace_cache_entry *entry;
+ struct hlist_head *hlist;
+
+ if (!c)
+ return NULL;
+
+ hlist = &c->hashtable[hash_32(key, c->bits)];
+ hlist_for_each_entry(entry, hlist, hash) {
+ if (entry->key == key)
+ return entry;
+ }
+
+ return NULL;
+}
diff --git a/tools/perf/util/itrace.h b/tools/perf/util/itrace.h
index 575037c..e67fa34 100644
--- a/tools/perf/util/itrace.h
+++ b/tools/perf/util/itrace.h
@@ -316,6 +316,20 @@ int itrace_heap__add(struct itrace_heap *heap, unsigned int queue_nr,
void itrace_heap__pop(struct itrace_heap *heap);
void itrace_heap__free(struct itrace_heap *heap);

+struct itrace_cache_entry {
+ struct hlist_node hash;
+ u32 key;
+};
+
+struct itrace_cache *itrace_cache__new(unsigned int bits, size_t entry_size,
+ unsigned int limit_percent);
+void itrace_cache__free(struct itrace_cache *itrace_cache);
+void *itrace_cache__alloc_entry(struct itrace_cache *c);
+void itrace_cache__free_entry(struct itrace_cache *c, void *entry);
+int itrace_cache__add(struct itrace_cache *c, u32 key,
+ struct itrace_cache_entry *entry);
+void *itrace_cache__lookup(struct itrace_cache *c, u32 key);
+
struct itrace_record *itrace_record__init(int *err);

int itrace_record__options(struct itrace_record *itr,
--
1.9.1