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authorEmilio G. Cota <cota@braap.org>2018-08-16 22:41:01 -0400
committerPaolo Bonzini <pbonzini@redhat.com>2018-08-23 18:46:25 +0200
commitd557de4a0e290c9946f37ff1fba7204844cccc64 (patch)
tree998b6461089c65f4a922f2c3087d8d0b871663cb
parent996e8d9a45f74fd59a8aa5fa78102e1d8981a945 (diff)
qsp: support call site coalescing
Signed-off-by: Emilio G. Cota <cota@braap.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--include/qemu/qsp.h2
-rw-r--r--util/qsp.c102
2 files changed, 89 insertions, 15 deletions
diff --git a/include/qemu/qsp.h b/include/qemu/qsp.h
index f8c6c9648a..a94c464f90 100644
--- a/include/qemu/qsp.h
+++ b/include/qemu/qsp.h
@@ -19,7 +19,7 @@ enum QSPSortBy {
};
void qsp_report(FILE *f, fprintf_function cpu_fprintf, size_t max,
- enum QSPSortBy sort_by);
+ enum QSPSortBy sort_by, bool callsite_coalesce);
bool qsp_is_enabled(void);
void qsp_enable(void);
diff --git a/util/qsp.c b/util/qsp.c
index 4b1308b081..4dc851e456 100644
--- a/util/qsp.c
+++ b/util/qsp.c
@@ -27,11 +27,9 @@
* Reports are generated as a table where each row represents a call site. A
* call site is the triplet formed by the __file__ and __LINE__ of the caller
* as well as the address of the "object" (i.e. mutex, rec. mutex or condvar)
- * being operated on. Focusing on call sites instead of just on objects might
- * seem puzzling. However, it is a sensible choice since otherwise dealing with
- * dynamically-allocated objects becomes difficult (e.g. what to do when an
- * object is destroyed, or reused?). Furthermore, the call site info is of most
- * importance, since it is callers, and not objects, what cause wait time.
+ * being operated on. Optionally, call sites that operate on different objects
+ * of the same type can be coalesced, which can be particularly useful when
+ * profiling dynamically-allocated objects.
*
* Alternative designs considered:
*
@@ -84,6 +82,7 @@ struct QSPEntry {
const QSPCallSite *callsite;
uint64_t n_acqs;
uint64_t ns;
+ unsigned int n_objs; /* count of coalesced objs; only used for reporting */
#ifndef CONFIG_ATOMIC64
/*
* If we cannot update the counts atomically, then use a seqlock.
@@ -170,6 +169,17 @@ static uint32_t qsp_entry_no_thread_hash(const QSPEntry *entry)
return do_qsp_entry_hash(entry, 0);
}
+/* without the objects we need to hash the file name to get a decent hash */
+static uint32_t qsp_entry_no_thread_obj_hash(const QSPEntry *entry)
+{
+ const QSPCallSite *callsite = entry->callsite;
+ uint64_t a = g_str_hash(callsite->file);
+ uint64_t b = callsite->line;
+ uint32_t e = callsite->type;
+
+ return tb_hash_func7(a, b, e, 0, 0);
+}
+
static bool qsp_callsite_cmp(const void *ap, const void *bp)
{
const QSPCallSite *a = ap;
@@ -182,6 +192,17 @@ static bool qsp_callsite_cmp(const void *ap, const void *bp)
(a->file == b->file || !strcmp(a->file, b->file)));
}
+static bool qsp_callsite_no_obj_cmp(const void *ap, const void *bp)
+{
+ const QSPCallSite *a = ap;
+ const QSPCallSite *b = bp;
+
+ return a == b ||
+ (a->line == b->line &&
+ a->type == b->type &&
+ (a->file == b->file || !strcmp(a->file, b->file)));
+}
+
static bool qsp_entry_no_thread_cmp(const void *ap, const void *bp)
{
const QSPEntry *a = ap;
@@ -190,6 +211,14 @@ static bool qsp_entry_no_thread_cmp(const void *ap, const void *bp)
return qsp_callsite_cmp(a->callsite, b->callsite);
}
+static bool qsp_entry_no_thread_obj_cmp(const void *ap, const void *bp)
+{
+ const QSPEntry *a = ap;
+ const QSPEntry *b = bp;
+
+ return qsp_callsite_no_obj_cmp(a->callsite, b->callsite);
+}
+
static bool qsp_entry_cmp(const void *ap, const void *bp)
{
const QSPEntry *a = ap;
@@ -548,15 +577,36 @@ static void qsp_diff(struct qht *orig, struct qht *new)
qht_iter(orig, qsp_iter_diff, new);
}
+static void
+qsp_iter_callsite_coalesce(struct qht *orig, void *p, uint32_t h, void *htp)
+{
+ struct qht *ht = htp;
+ QSPEntry *old = p;
+ QSPEntry *e;
+ uint32_t hash;
+
+ hash = qsp_entry_no_thread_obj_hash(old);
+ e = qht_lookup(ht, old, hash);
+ if (e == NULL) {
+ e = qsp_entry_create(ht, old, hash);
+ e->n_objs = 1;
+ } else if (e->callsite->obj != old->callsite->obj) {
+ e->n_objs++;
+ }
+ e->ns += old->ns;
+ e->n_acqs += old->n_acqs;
+}
+
static void qsp_ht_delete(struct qht *ht, void *p, uint32_t h, void *htp)
{
g_free(p);
}
-static void qsp_mktree(GTree *tree)
+static void qsp_mktree(GTree *tree, bool callsite_coalesce)
{
QSPSnapshot *snap;
- struct qht ht;
+ struct qht ht, coalesce_ht;
+ struct qht *htp;
/*
* First, see if there's a prior snapshot, so that we read the global hash
@@ -581,11 +631,23 @@ static void qsp_mktree(GTree *tree)
/* done with the snapshot; RCU can reclaim it */
rcu_read_unlock();
+ htp = &ht;
+ if (callsite_coalesce) {
+ qht_init(&coalesce_ht, qsp_entry_no_thread_obj_cmp, QSP_INITIAL_SIZE,
+ QHT_MODE_AUTO_RESIZE | QHT_MODE_RAW_MUTEXES);
+ qht_iter(&ht, qsp_iter_callsite_coalesce, &coalesce_ht);
+
+ /* free the previous hash table, and point htp to coalesce_ht */
+ qht_iter(&ht, qsp_ht_delete, NULL);
+ qht_destroy(&ht);
+ htp = &coalesce_ht;
+ }
+
/* sort the hash table elements by using a tree */
- qht_iter(&ht, qsp_sort, tree);
+ qht_iter(htp, qsp_sort, tree);
/* free the hash table, but keep the elements (those are in the tree now) */
- qht_destroy(&ht);
+ qht_destroy(htp);
}
/* free string with g_free */
@@ -611,6 +673,7 @@ struct QSPReportEntry {
double time_s;
double ns_avg;
uint64_t n_acqs;
+ unsigned int n_objs;
};
typedef struct QSPReportEntry QSPReportEntry;
@@ -634,6 +697,7 @@ static gboolean qsp_tree_report(gpointer key, gpointer value, gpointer udata)
report->n_entries++;
entry->obj = e->callsite->obj;
+ entry->n_objs = e->n_objs;
entry->callsite_at = qsp_at(e->callsite);
entry->typename = qsp_typenames[e->callsite->type];
entry->time_s = e->ns * 1e-9;
@@ -678,10 +742,20 @@ pr_report(const QSPReport *rep, FILE *f, fprintf_function pr)
for (i = 0; i < rep->n_entries; i++) {
const QSPReportEntry *e = &rep->entries[i];
+ GString *s = g_string_new(NULL);
- pr(f, "%-9s %14p %s%*s %13.5f %12" PRIu64 " %12.2f\n", e->typename,
- e->obj, e->callsite_at, callsite_len - (int)strlen(e->callsite_at),
- "", e->time_s, e->n_acqs, e->ns_avg * 1e-3);
+ g_string_append_printf(s, "%-9s ", e->typename);
+ if (e->n_objs > 1) {
+ g_string_append_printf(s, "[%12u]", e->n_objs);
+ } else {
+ g_string_append_printf(s, "%14p", e->obj);
+ }
+ g_string_append_printf(s, " %s%*s %13.5f %12" PRIu64 " %12.2f\n",
+ e->callsite_at,
+ callsite_len - (int)strlen(e->callsite_at), "",
+ e->time_s, e->n_acqs, e->ns_avg * 1e-3);
+ pr(f, "%s", s->str);
+ g_string_free(s, TRUE);
}
pr(f, "%s\n", dashes);
@@ -701,7 +775,7 @@ static void report_destroy(QSPReport *rep)
}
void qsp_report(FILE *f, fprintf_function cpu_fprintf, size_t max,
- enum QSPSortBy sort_by)
+ enum QSPSortBy sort_by, bool callsite_coalesce)
{
GTree *tree = g_tree_new_full(qsp_tree_cmp, &sort_by, g_free, NULL);
QSPReport rep;
@@ -712,7 +786,7 @@ void qsp_report(FILE *f, fprintf_function cpu_fprintf, size_t max,
rep.n_entries = 0;
rep.max_n_entries = max;
- qsp_mktree(tree);
+ qsp_mktree(tree, callsite_coalesce);
g_tree_foreach(tree, qsp_tree_report, &rep);
g_tree_destroy(tree);