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qsp: support call site coalescing

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Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Emilio G. Cota 2018-08-16 22:41:01 -04:00 committed by Paolo Bonzini
parent 996e8d9a45
commit d557de4a0e
2 changed files with 89 additions and 15 deletions
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2
include/qemu/qsp.h
View file

@ -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);

102
util/qsp.c
View file

@ -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);