I was able to reproduce this overhead issue on my machine. This patch fixed it.
Acked-by: Christian Babeux <christian.bab...@efficios.com> On Wed, Jan 16, 2013 at 10:14 AM, Mathieu Desnoyers <mathieu.desnoy...@efficios.com> wrote: > lttng_create_event_if_missing() takes a lot of CPU time with stress-test > applications containing 1000 different TRACEPOINT_EVENT() and 1000 > individual tracepoint() call-site. > > With tracing disabled: > > time ./AppWith1000_lines_TP 0 > > real 0m2.487s > user 0m2.424s > sys 0m0.000s > > > Introducing this hash table cuts the overhead very significantly when > tracing is enabled: > > Before patch: > > 72.16% AppWith1000_lin liblttng-ust.so.0.0.0 [.] > lttng_create_event_if_missing > 25.64% AppWith1000_lin AppWith1000_lines_TP [.] a(int) > > time ./AppWith1000_lines_TP 0 > > real 0m7.946s > user 0m7.864s > sys 0m0.000s > > > After patch: > > 89.13% AppWith1000_lin AppWith1000_lines_TP [.] a(int) > 3.30% AppWith1000_lin liblttng-ust.so.0.0.0 [.] > lttng_create_event_if_missing > > time ./AppWith1000_lines_TP 0 > > real 0m2.762s > user 0m2.692s > sys 0m0.004s > > Signed-off-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com> > --- > diff --git a/include/lttng/ust-events.h b/include/lttng/ust-events.h > index 095fb1e..1db8e58 100644 > --- a/include/lttng/ust-events.h > +++ b/include/lttng/ust-events.h > @@ -362,6 +362,7 @@ struct lttng_event { > int has_enablers_without_bytecode; > /* Backward references: list of lttng_enabler_ref (ref to enablers) */ > struct cds_list_head enablers_ref_head; > + struct cds_hlist_node hlist; /* session ht of events */ > }; > > struct channel; > @@ -467,6 +468,7 @@ struct lttng_session { > /* New UST 2.1 */ > /* List of enablers */ > struct cds_list_head enablers_head; > + struct lttng_ust_event_ht events_ht; /* ht of events */ > }; > > struct lttng_transport { > diff --git a/liblttng-ust/lttng-events.c b/liblttng-ust/lttng-events.c > index 5e6c90c..f70c65f 100644 > --- a/liblttng-ust/lttng-events.c > +++ b/liblttng-ust/lttng-events.c > @@ -127,7 +127,7 @@ void synchronize_trace(void) > struct lttng_session *lttng_session_create(void) > { > struct lttng_session *session; > - int ret; > + int ret, i; > > session = zmalloc(sizeof(struct lttng_session)); > if (!session) > @@ -135,6 +135,8 @@ struct lttng_session *lttng_session_create(void) > CDS_INIT_LIST_HEAD(&session->chan_head); > CDS_INIT_LIST_HEAD(&session->events_head); > CDS_INIT_LIST_HEAD(&session->enablers_head); > + for (i = 0; i < LTTNG_UST_EVENT_HT_SIZE; i++) > + CDS_INIT_HLIST_HEAD(&session->events_ht.table[i]); > ret = lttng_ust_uuid_generate(session->uuid); > if (ret != 0) { > session->uuid[0] = '\0'; > @@ -329,17 +331,19 @@ int lttng_event_create(const struct lttng_event_desc > *desc, > { > const char *event_name = desc->name; > struct lttng_event *event; > + struct cds_hlist_head *head; > + struct cds_hlist_node *node; > int ret = 0; > + size_t name_len = strlen(event_name); > + uint32_t hash; > > if (chan->used_event_id == -1U) { > ret = -ENOMEM; > goto full; > } > - /* > - * This is O(n^2) (for each event, the loop is called at event > - * creation). Might require a hash if we have lots of events. > - */ > - cds_list_for_each_entry(event, &chan->session->events_head, node) { > + hash = jhash(event_name, name_len, 0); > + head = &chan->session->events_ht.table[hash & > (LTTNG_UST_EVENT_HT_SIZE - 1)]; > + cds_hlist_for_each_entry(event, node, head, hlist) { > assert(event->desc); > if (!strncmp(event->desc->name, > desc->name, > @@ -380,6 +384,7 @@ int lttng_event_create(const struct lttng_event_desc > *desc, > if (ret) > goto statedump_error; > cds_list_add(&event->node, &chan->session->events_head); > + cds_hlist_add_head(&event->hlist, head); > return 0; > > statedump_error: > @@ -499,17 +504,24 @@ void lttng_create_event_if_missing(struct lttng_enabler > *enabler) > cds_list_for_each_entry(probe_desc, probe_list, head) { > for (i = 0; i < probe_desc->nr_events; i++) { > int found = 0, ret; > + struct cds_hlist_head *head; > + struct cds_hlist_node *node; > + const char *event_name; > + size_t name_len; > + uint32_t hash; > > desc = probe_desc->event_desc[i]; > if (!lttng_desc_match_enabler(desc, enabler)) > continue; > + event_name = desc->name; > + name_len = strlen(event_name); > > /* > - * For each event in session event list, > - * check if already created. > + * Check if already created. > */ > - cds_list_for_each_entry(event, > - &session->events_head, node) { > + hash = jhash(event_name, name_len, 0); > + head = &session->events_ht.table[hash & > (LTTNG_UST_EVENT_HT_SIZE - 1)]; > + cds_hlist_for_each_entry(event, node, head, hlist) { > if (event->desc == desc) > found = 1; > } > > -- > Mathieu Desnoyers > EfficiOS Inc. > http://www.efficios.com > > _______________________________________________ > lttng-dev mailing list > lttng-dev@lists.lttng.org > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev