Re: [PATCH v4 2/7] perf/sdt: Directly record SDT events with 'perf record'

From: Masami Hiramatsu
Date: Wed Mar 08 2017 - 07:37:11 EST

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Hi Ravi,

On Mon, 6 Mar 2017 18:42:59 +0530
Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxxxxxxx> wrote:

> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index bc84a37..e87b19b 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -39,6 +39,7 @@
> #include "util/trigger.h"
> #include "util/perf-hooks.h"
> #include "asm/bug.h"
> +#include "util/probe-file.h"
>
> #include <unistd.h>
> #include <sched.h>
> @@ -73,6 +74,7 @@ struct record {
> bool timestamp_filename;
> struct switch_output switch_output;
> unsigned long long samples;
> + struct list_head sdt_event_list;
> };
>
> static volatile int auxtrace_record__snapshot_started;
> @@ -1503,6 +1505,26 @@ static struct record record = {
> },
> };
>
> +void sdt_event_list__add(struct list_head *sdt_event_list)
> +{
> + if (list_empty(sdt_event_list))
> + return;
> + list_splice(sdt_event_list, &record.sdt_event_list);
> +}
> +
> +bool is_cmd_record(void)
> +{
> + return (record.evlist != NULL);
> +}

Hmm, exporting this from builtin-record.c makes inverted reference from
builtin-record.o to libperf. I think it is not good way to do.

[...]
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 54355d3..1fcc9d13 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -1727,12 +1727,66 @@ static void parse_events_print_error(struct parse_events_error *err,
>
> #undef MAX_WIDTH
>
> +/* SDT event needs LIBELF support for creating a probe point */
> +#ifdef HAVE_LIBELF_SUPPORT
> +static int parse_sdt_event(struct perf_evlist *evlist, const char *str,
> + struct parse_events_error *err)
> +{
> + char *ptr = NULL;
> + int ret;
> + struct list_head *sdt_evlist;
> + struct sdt_event_list *sdt_event;
> +
> + if (str[0] == '%')
> + str++;
> +
> + ptr = strdup(str);
> + if (ptr == NULL)
> + return -ENOMEM;
> +
> + sdt_evlist = zalloc(sizeof(*sdt_evlist));
> + if (!sdt_evlist) {
> + free(ptr);
> + pr_debug("Error in sdt_evlist memory allocation\n");
> + return -ENOMEM;
> + }
> + INIT_LIST_HEAD(sdt_evlist);
> +
> + /*
> + * If there is an error in this call, no need to free
> + * up sdt_evlist, its already free'ed up in the previous
> + * call. Free up 'ptr' though.
> + */
> + ret = add_sdt_event(ptr, sdt_evlist);
> + if (!ret) {
> + list_for_each_entry(sdt_event, sdt_evlist, list) {
> + ret = parse_events(evlist, sdt_event->name, err);
> + if (ret < 0)
> + goto ret;
> + }
> + /* Add it to the record struct */
> + sdt_event_list__add(sdt_evlist);
> + }
> +
> +ret:
> + free(ptr);
> + return ret;
> +}
> +#endif /* HAVE_LIBELF_SUPPORT */
> +
> int parse_events_option(const struct option *opt, const char *str,
> int unset __maybe_unused)
> {
> struct perf_evlist *evlist = *(struct perf_evlist **)opt->value;
> struct parse_events_error err = { .idx = 0, };
> - int ret = parse_events(evlist, str, &err);
> + int ret = 0;
> +
> +#ifdef HAVE_LIBELF_SUPPORT
> + if (is_sdt_event((char *)str) && is_cmd_record())
> + ret = parse_sdt_event(evlist, str, &err);
> + else
> +#endif

To avoid these ifdefs, could you add a dummy (error return) function
of add_sdt_event() for !HAVE_LIBELF_SUPPORT case in probe-event.h?

> + ret = parse_events(evlist, str, &err);
>
> if (ret)
> parse_events_print_error(&err, str);
> diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
> index c6172cd..0887269 100644
> --- a/tools/perf/util/parse-events.h
> +++ b/tools/perf/util/parse-events.h
> @@ -208,4 +208,6 @@ static inline bool is_sdt_event(char *str)
> (!strncmp(str, "sdt_", 4) &&
> !!strchr(str, ':') && !strchr(str, '=')));
> }
> +
> +void sdt_event_list__add(struct list_head *sdt_event_list);
> #endif /* __PERF_PARSE_EVENTS_H */
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index 2b1409f..b879076 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -1293,7 +1293,7 @@ int parse_line_range_desc(const char *arg, struct line_range *lr)
> return err;
> }
>
> -static int parse_perf_probe_event_name(char **arg, struct perf_probe_event *pev)
> +int parse_perf_probe_event_name(char **arg, struct perf_probe_event *pev)
> {
> char *ptr;
>
> @@ -3125,8 +3125,8 @@ static int find_cached_events(struct perf_probe_event *pev,
> }
>
> /* Try to find probe_trace_event from all probe caches */
> -static int find_cached_events_all(struct perf_probe_event *pev,
> - struct probe_trace_event **tevs)
> +int find_cached_events_all(struct perf_probe_event *pev,
> + struct probe_trace_event **tevs)
> {
> struct probe_trace_event *tmp_tevs = NULL;
> struct strlist *bidlist;
> @@ -3476,3 +3476,32 @@ int copy_to_probe_trace_arg(struct probe_trace_arg *tvar,
> tvar->name = NULL;
> return 0;
> }
> +
> +/*
> + * Record session for SDT events has ended. Delete the SDT events
> + * from uprobe_events file that were created initially.
> + */
> +void remove_sdt_event_list(struct list_head *sdt_events)
> +{
> + struct sdt_event_list *sdt_event;
> + struct strfilter *filter = NULL;
> + const char *err = NULL;
> +
> + if (list_empty(sdt_events))
> + return;
> +
> + list_for_each_entry(sdt_event, sdt_events, list) {
> + if (!filter) {
> + filter = strfilter__new(sdt_event->name, &err);
> + if (!filter)
> + goto free_list;
> + } else {
> + strfilter__or(filter, sdt_event->name, &err);
> + }
> + }
> +
> + del_perf_probe_events(filter);
> +
> +free_list:
> + free_sdt_list(sdt_events);
> +}
> diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
> index 5d4e940..91e277e 100644
> --- a/tools/perf/util/probe-event.h
> +++ b/tools/perf/util/probe-event.h
> @@ -182,4 +182,8 @@ struct map *get_target_map(const char *target, bool user);
> void arch__post_process_probe_trace_events(struct perf_probe_event *pev,
> int ntevs);
>
> +int parse_perf_probe_event_name(char **arg, struct perf_probe_event *pev);
> +
> +int find_cached_events_all(struct perf_probe_event *pev,
> + struct probe_trace_event **tevs);
> #endif /*_PROBE_EVENT_H */
> diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
> index 1a62dac..c1cf67f 100644
> --- a/tools/perf/util/probe-file.c
> +++ b/tools/perf/util/probe-file.c
> @@ -27,8 +27,10 @@
> #include "probe-event.h"
> #include "probe-file.h"
> #include "session.h"
> +#include "probe-finder.h"
>
> #define MAX_CMDLEN 256
> +#define MAX_EVENT_LENGTH 512
>
> static void print_open_warning(int err, bool uprobe)
> {
> @@ -935,3 +937,132 @@ bool probe_type_is_available(enum probe_type type)
>
> return ret;
> }
> +
> +void free_sdt_list(struct list_head *sdt_evlist)
> +{
> + struct sdt_event_list *tmp, *ptr;
> +
> + if (list_empty(sdt_evlist))
> + return;
> + list_for_each_entry_safe(tmp, ptr, sdt_evlist, list) {
> + list_del(&tmp->list);
> + free(tmp->name);
> + free(tmp);
> + }
> +}
> +
> +static int get_sdt_events_from_cache(struct perf_probe_event *pev)
> +{
> + int ret = 0;
> +
> + pev->ntevs = find_cached_events_all(pev, &pev->tevs);
> +
> + if (pev->ntevs < 0) {
> + pr_err("Error: Cache lookup failed (code: %d)\n", pev->ntevs);
> + ret = pev->ntevs;
> + } else if (!pev->ntevs) {
> + pr_err("Error: %s:%s not found in the cache\n",
> + pev->group, pev->event);
> + ret = -EINVAL;
> + } else if (pev->ntevs > 1) {
> + pr_warning("Warning : Recording on %d occurences of %s:%s\n",
> + pev->ntevs, pev->group, pev->event);
> + }
> +
> + return ret;
> +}
> +
> +static int add_event_to_sdt_evlist(struct probe_trace_event *tev,
> + struct list_head *sdt_evlist)
> +{
> + struct sdt_event_list *tmp;
> +
> + tmp = zalloc(sizeof(*tmp));
> + if (!tmp)
> + return -ENOMEM;
> +
> + INIT_LIST_HEAD(&tmp->list);
> + tmp->name = zalloc(MAX_EVENT_LENGTH * sizeof(char));
> + if (!tmp->name)
> + return -ENOMEM;
> +
> + snprintf(tmp->name, strlen(tev->group) + strlen(tev->event) + 2,
> + "%s:%s", tev->group, tev->event);
> + list_add(&tmp->list, sdt_evlist);
> +
> + return 0;
> +}
> +
> +static int add_events_to_sdt_evlist(struct perf_probe_event *pev,
> + struct list_head *sdt_evlist)
> +{
> + int i, ret;
> +
> + for (i = 0; i < pev->ntevs; i++) {
> + ret = add_event_to_sdt_evlist(&pev->tevs[i], sdt_evlist);
> +
> + if (ret < 0)
> + return ret;
> + }
> + return 0;
> +}
> +
> +/*
> + * Find the SDT event from the cache and if found add it/them
> + * to the uprobe_events file
> + */
> +int add_sdt_event(char *event, struct list_head *sdt_evlist)
> +{
> + struct perf_probe_event *pev;
> + int ret;
> +
> + pev = zalloc(sizeof(*pev));
> + if (!pev)
> + return -ENOMEM;
> +
> + pev->sdt = true;
> + pev->uprobes = true;
> +
> + /*
> + * Parse event to find the group name and event name of
> + * the sdt event.
> + */
> + ret = parse_perf_probe_event_name(&event, pev);
> + if (ret) {
> + pr_err("Error in parsing sdt event %s\n", event);
> + free(pev);
> + return ret;
> + }
> +
> + probe_conf.max_probes = MAX_PROBES;
> + probe_conf.force_add = 1;
> +
> + /* Fetch all matching events from cache. */
> + ret = get_sdt_events_from_cache(pev);
> + if (ret < 0)
> + goto free_pev;
> +
> + /*
> + * Create probe point for all events by adding them in
> + * uprobe_events file
> + */
> + ret = apply_perf_probe_events(pev, 1);
> + if (ret) {
> + pr_err("Error in adding SDT event : %s\n", event);
> + goto free_pev;
> + }
> +
> + /* Add events to sdt_evlist */
> + ret = add_events_to_sdt_evlist(pev, sdt_evlist);
> + if (ret < 0)
> + goto free_pev;
> +
> + ret = 0;
> +
> +free_pev:
> + if (ret < 0)
> + free_sdt_list(sdt_evlist);
> + cleanup_perf_probe_events(pev, 1);
> + free(pev);
> + return ret;
> +}

Hmm, why would you put this function in probe-file.c? I would like to
ask you move this kind of functions which operates perf_probe_event
in probe-event.c.

Thanks,

> diff --git a/tools/perf/util/probe-file.h b/tools/perf/util/probe-file.h
> index a17a82e..6d2d3e5 100644
> --- a/tools/perf/util/probe-file.h
> +++ b/tools/perf/util/probe-file.h
> @@ -19,6 +19,11 @@ struct probe_cache {
> struct list_head entries;
> };
>
> +struct sdt_event_list {
> + char *name; /* group:event */
> + struct list_head list;
> +};
> +
> enum probe_type {
> PROBE_TYPE_U = 0,
> PROBE_TYPE_S,
> @@ -65,6 +70,9 @@ struct probe_cache_entry *probe_cache__find_by_name(struct probe_cache *pcache,
> const char *group, const char *event);
> int probe_cache__show_all_caches(struct strfilter *filter);
> bool probe_type_is_available(enum probe_type type);
> +int add_sdt_event(char *event, struct list_head *sdt_event_list);
> +void remove_sdt_event_list(struct list_head *sdt_event_list);
> +void free_sdt_list(struct list_head *sdt_events);
> #else /* ! HAVE_LIBELF_SUPPORT */
> static inline struct probe_cache *probe_cache__new(const char *tgt __maybe_unused)
> {
> --
> 2.9.3
>

--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>

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