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Date:   Mon, 15 Jun 2020 18:58:02 +0200
From:   Jiri Olsa <jolsa@redhat.com>
To:     Alexey Budankov <alexey.budankov@linux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Andi Kleen <ak@linux.intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v7 01/13] tools/libperf: introduce notion of static
 polled file descriptors
Message-ID: <20200615165802.GD2088119@krava>
References: <20200605105051.GA1404794@krava>
 <20200605113834.GC1404794@krava>
 <be40edeb-0cb9-5e11-2a22-8392316cdced@linux.intel.com>
 <49eca46e-4d0e-2ae5-d7d9-e37a4d680270@linux.intel.com>
 <20200608084344.GA1520715@krava>
 <2d80a43a-54cf-3d12-92fd-066217c95d76@linux.intel.com>
 <20200608160758.GD1558310@krava>
 <bde9bcc3-9ec0-6e37-26f6-139b038ad3de@linux.intel.com>
 <20200615123048.GB2088119@krava>
 <8b29e324-eb8d-2266-562b-ca46aec76a3e@linux.intel.com>
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On Mon, Jun 15, 2020 at 05:37:53PM +0300, Alexey Budankov wrote:
> 
> On 15.06.2020 15:30, Jiri Olsa wrote:
> > On Mon, Jun 15, 2020 at 08:20:38AM +0300, Alexey Budankov wrote:
> >>
> >> On 08.06.2020 19:07, Jiri Olsa wrote:
> >>> On Mon, Jun 08, 2020 at 12:54:31PM +0300, Alexey Budankov wrote:
> >>>>
> >>>> On 08.06.2020 11:43, Jiri Olsa wrote:
> >>>>> On Mon, Jun 08, 2020 at 11:08:56AM +0300, Alexey Budankov wrote:
> >>>>>>
> >>>>>> On 05.06.2020 19:15, Alexey Budankov wrote:
> >>>>>>>
> >>>>>>> On 05.06.2020 14:38, Jiri Olsa wrote:
> >> <SNIP>
> >>>>>>> revents = fdarray_fixed_revents(array, pos);
> >>>>>>> fdarray__del(array, pos);
> >>>>>>
> >>>>>> So how is it about just adding _revents() and _del() for fixed fds with
> >>>>>> correction of retval to bool for fdarray__add()?
> >>>>>
> >>>>> I don't like the separation for fixed and non-fixed fds,
> >>>>> why can't we make generic?
> >>>>
> >>>> Usage models are different but they want still to be parts of the same class
> >>>> for atomic poll(). The distinction is filterable vs. not filterable.
> >>>> The distinction should be somehow provided in API. Options are:
> >>>> 1. expose separate API calls like __add_nonfilterable(), __del_nonfilterable();
> >>>>    use nonfilterable quality in __filter() and __poll() and, perhaps, other internals;
> >>>> 2. extend fdarray__add(, nonfilterable) with the nonfilterable quality
> >>>>    use the type in __filter() and __poll() and, perhaps, other internals;
> >>>>    expose less API calls in comparison with option 1
> >>>>
> >>>> Exposure of pos for filterable fds should be converted to bool since currently
> >>>> the returned pos can become stale and there is no way in API to check its state.
> >>>> So it could look like this:
> >>>>
> >>>> fdkey = fdarray__add(array, fd, events, type)
> >>>> type: filterable, nonfilterable, somthing else
> >>>> revents = fdarray__get_revents(fdkey);
> >>>> fdarray__del(array, fdkey);
> >>>
> >>> I think there's solution without having filterable type,
> >>> I'm not sure why you think this is needed
> >>>
> >>> I'm busy with other things this week, but I think I can
> >>> come up with some patch early next week if needed
> >>
> >> Friendly reminder.
> > 
> > hm? I believe we discussed this in here:
> >   https://lore.kernel.org/lkml/20200609145611.GI1558310@krava/
> 
> Do you want it to be implemented like in the patch posted by the link?

no idea.. looking for good solution ;-)

how about switching completely to epoll? I tried and it
does not look that bad

there might be some loose ends (interface change), but
I think this would solve our problems with fdarray

I'll be able to get back to it by the end of the week,
but if you want to check/finish this patch earlier go ahead

jirka


---
 tools/lib/perf/evlist.c                  | 134 +++++++++++++++++------
 tools/lib/perf/include/internal/evlist.h |   9 +-
 tools/perf/builtin-kvm.c                 |   8 +-
 tools/perf/builtin-record.c              |  14 ++-
 4 files changed, 120 insertions(+), 45 deletions(-)

diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c
index 6a875a0f01bb..8569cdd8bbd8 100644
--- a/tools/lib/perf/evlist.c
+++ b/tools/lib/perf/evlist.c
@@ -23,6 +23,7 @@
 #include <perf/cpumap.h>
 #include <perf/threadmap.h>
 #include <api/fd/array.h>
+#include <sys/epoll.h>
 
 void perf_evlist__init(struct perf_evlist *evlist)
 {
@@ -32,7 +33,10 @@ void perf_evlist__init(struct perf_evlist *evlist)
 		INIT_HLIST_HEAD(&evlist->heads[i]);
 	INIT_LIST_HEAD(&evlist->entries);
 	evlist->nr_entries = 0;
-	fdarray__init(&evlist->pollfd, 64);
+	INIT_LIST_HEAD(&evlist->poll_data);
+	evlist->poll_cnt = 0;
+	evlist->poll_act = 0;
+	evlist->poll_fd = -1;
 }
 
 static void __perf_evlist__propagate_maps(struct perf_evlist *evlist,
@@ -120,6 +124,23 @@ static void perf_evlist__purge(struct perf_evlist *evlist)
 	evlist->nr_entries = 0;
 }
 
+struct poll_data {
+	int		  fd;
+	void		 *ptr;
+	struct list_head  list;
+};
+
+static void perf_evlist__exit_pollfd(struct perf_evlist *evlist)
+{
+	struct poll_data *data, *tmp;
+
+	if (evlist->poll_fd != -1)
+		close(evlist->poll_fd);
+
+	list_for_each_entry_safe(data, tmp, &evlist->poll_data, list)
+		free(data);
+}
+
 void perf_evlist__exit(struct perf_evlist *evlist)
 {
 	perf_cpu_map__put(evlist->cpus);
@@ -128,7 +149,7 @@ void perf_evlist__exit(struct perf_evlist *evlist)
 	evlist->cpus = NULL;
 	evlist->all_cpus = NULL;
 	evlist->threads = NULL;
-	fdarray__exit(&evlist->pollfd);
+	perf_evlist__exit_pollfd(evlist);
 }
 
 void perf_evlist__delete(struct perf_evlist *evlist)
@@ -285,56 +306,105 @@ int perf_evlist__id_add_fd(struct perf_evlist *evlist,
 
 int perf_evlist__alloc_pollfd(struct perf_evlist *evlist)
 {
-	int nr_cpus = perf_cpu_map__nr(evlist->cpus);
-	int nr_threads = perf_thread_map__nr(evlist->threads);
-	int nfds = 0;
-	struct perf_evsel *evsel;
-
-	perf_evlist__for_each_entry(evlist, evsel) {
-		if (evsel->system_wide)
-			nfds += nr_cpus;
-		else
-			nfds += nr_cpus * nr_threads;
-	}
+	int poll_fd;
 
-	if (fdarray__available_entries(&evlist->pollfd) < nfds &&
-	    fdarray__grow(&evlist->pollfd, nfds) < 0)
-		return -ENOMEM;
+	poll_fd = epoll_create1(EPOLL_CLOEXEC);
+	if (!poll_fd)
+		return -1;
 
+	evlist->poll_fd = poll_fd;
 	return 0;
 }
 
-int perf_evlist__add_pollfd(struct perf_evlist *evlist, int fd,
-			    void *ptr, short revent)
+static int __perf_evlist__add_pollfd(struct perf_evlist *evlist,
+				     struct poll_data *data,
+				     short revent)
 {
-	int pos = fdarray__add(&evlist->pollfd, fd, revent | POLLERR | POLLHUP);
+	struct epoll_event *events, ev = {
+		.data.ptr = data,
+		.events   = revent | EPOLLERR | EPOLLHUP,
+	};
+	int err;
+
+	err = epoll_ctl(evlist->poll_fd, EPOLL_CTL_ADD, data->fd, &ev);
+	if (err)
+		return err;
 
-	if (pos >= 0) {
-		evlist->pollfd.priv[pos].ptr = ptr;
-		fcntl(fd, F_SETFL, O_NONBLOCK);
+	events = realloc(evlist->poll_events, sizeof(ev) * evlist->poll_cnt);
+	if (events) {
+		evlist->poll_events = events;
+		evlist->poll_cnt++;
 	}
 
-	return pos;
+	return events ? 0 : -ENOMEM;
 }
 
-static void perf_evlist__munmap_filtered(struct fdarray *fda, int fd,
-					 void *arg __maybe_unused)
+int perf_evlist__add_pollfd(struct perf_evlist *evlist, int fd,
+			    void *ptr, short revent)
 {
-	struct perf_mmap *map = fda->priv[fd].ptr;
+	struct poll_data *data = zalloc(sizeof(*data));
+	int err;
 
-	if (map)
-		perf_mmap__put(map);
+	if (!data)
+		return -ENOMEM;
+
+	data->fd  = fd;
+	data->ptr = ptr;
+
+	err = __perf_evlist__add_pollfd(evlist, data, revent);
+	if (!err)
+		list_add_tail(&data->list, &evlist->poll_data);
+
+	return err;
 }
 
 int perf_evlist__filter_pollfd(struct perf_evlist *evlist, short revents_and_mask)
 {
-	return fdarray__filter(&evlist->pollfd, revents_and_mask,
-			       perf_evlist__munmap_filtered, NULL);
+	struct epoll_event *events = evlist->poll_events;
+	int i, removed = 0;
+
+	for (i = 0; i < evlist->poll_act; i++) {
+		if (events[i].events & revents_and_mask) {
+			struct poll_data *data = events[i].data.ptr;
+
+			if (data->ptr)
+				perf_mmap__put(data->ptr);
+
+			epoll_ctl(evlist->poll_fd, EPOLL_CTL_DEL, data->fd, &events[i]);
+
+			list_del(&data->list);
+			free(data);
+			removed++;
+		}
+	}
+
+	return evlist->poll_cnt -= removed;
+}
+
+bool perf_evlist__pollfd_data(struct perf_evlist *evlist, int fd)
+{
+	int i;
+
+	if (evlist->poll_act < 0)
+		return false;
+
+	for (i = 0; i < evlist->poll_act; i++) {
+		struct poll_data *data = evlist->poll_events[i].data.ptr;
+
+		if (data->fd == fd)
+			return true;
+	}
+
+	return false;
 }
 
 int perf_evlist__poll(struct perf_evlist *evlist, int timeout)
 {
-	return fdarray__poll(&evlist->pollfd, timeout);
+	evlist->poll_act = epoll_wait(evlist->poll_fd,
+				      evlist->poll_events,
+				      evlist->poll_cnt,
+				      timeout);
+	return evlist->poll_act;
 }
 
 static struct perf_mmap* perf_evlist__alloc_mmap(struct perf_evlist *evlist, bool overwrite)
@@ -593,7 +663,7 @@ int perf_evlist__mmap_ops(struct perf_evlist *evlist,
 			return -ENOMEM;
 	}
 
-	if (evlist->pollfd.entries == NULL && perf_evlist__alloc_pollfd(evlist) < 0)
+	if (evlist->poll_fd == -1 && perf_evlist__alloc_pollfd(evlist) < 0)
 		return -ENOMEM;
 
 	if (perf_cpu_map__empty(cpus))
diff --git a/tools/lib/perf/include/internal/evlist.h b/tools/lib/perf/include/internal/evlist.h
index 74dc8c3f0b66..39b08a04b992 100644
--- a/tools/lib/perf/include/internal/evlist.h
+++ b/tools/lib/perf/include/internal/evlist.h
@@ -3,7 +3,6 @@
 #define __LIBPERF_INTERNAL_EVLIST_H
 
 #include <linux/list.h>
-#include <api/fd/array.h>
 #include <internal/evsel.h>
 
 #define PERF_EVLIST__HLIST_BITS 8
@@ -12,6 +11,7 @@
 struct perf_cpu_map;
 struct perf_thread_map;
 struct perf_mmap_param;
+struct epoll_event;
 
 struct perf_evlist {
 	struct list_head	 entries;
@@ -22,7 +22,11 @@ struct perf_evlist {
 	struct perf_thread_map	*threads;
 	int			 nr_mmaps;
 	size_t			 mmap_len;
-	struct fdarray		 pollfd;
+	int			 poll_fd;
+	int			 poll_cnt;
+	int			 poll_act;
+	struct epoll_event	*poll_events;
+	struct list_head	 poll_data;
 	struct hlist_head	 heads[PERF_EVLIST__HLIST_SIZE];
 	struct perf_mmap	*mmap;
 	struct perf_mmap	*mmap_ovw;
@@ -124,4 +128,5 @@ int perf_evlist__id_add_fd(struct perf_evlist *evlist,
 			   struct perf_evsel *evsel,
 			   int cpu, int thread, int fd);
 
+bool perf_evlist__pollfd_data(struct perf_evlist *evlist, int fd);
 #endif /* __LIBPERF_INTERNAL_EVLIST_H */
diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index 95a77058023e..decc75745395 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -940,7 +940,7 @@ static int perf_kvm__handle_stdin(void)
 
 static int kvm_events_live_report(struct perf_kvm_stat *kvm)
 {
-	int nr_stdin, ret, err = -EINVAL;
+	int ret, err = -EINVAL;
 	struct termios save;
 
 	/* live flag must be set first */
@@ -971,8 +971,7 @@ static int kvm_events_live_report(struct perf_kvm_stat *kvm)
 	if (evlist__add_pollfd(kvm->evlist, kvm->timerfd) < 0)
 		goto out;
 
-	nr_stdin = evlist__add_pollfd(kvm->evlist, fileno(stdin));
-	if (nr_stdin < 0)
+	if (evlist__add_pollfd(kvm->evlist, fileno(stdin)))
 		goto out;
 
 	if (fd_set_nonblock(fileno(stdin)) != 0)
@@ -982,7 +981,6 @@ static int kvm_events_live_report(struct perf_kvm_stat *kvm)
 	evlist__enable(kvm->evlist);
 
 	while (!done) {
-		struct fdarray *fda = &kvm->evlist->core.pollfd;
 		int rc;
 
 		rc = perf_kvm__mmap_read(kvm);
@@ -993,7 +991,7 @@ static int kvm_events_live_report(struct perf_kvm_stat *kvm)
 		if (err)
 			goto out;
 
-		if (fda->entries[nr_stdin].revents & POLLIN)
+		if (perf_evlist__pollfd_data(&kvm->evlist->core, fileno(stdin)))
 			done = perf_kvm__handle_stdin();
 
 		if (!rc && !done)
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index e108d90ae2ed..a49bf4186aab 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1576,12 +1576,6 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 		status = -1;
 		goto out_delete_session;
 	}
-	err = evlist__add_pollfd(rec->evlist, done_fd);
-	if (err < 0) {
-		pr_err("Failed to add wakeup eventfd to poll list\n");
-		status = err;
-		goto out_delete_session;
-	}
 #endif // HAVE_EVENTFD_SUPPORT
 
 	session->header.env.comp_type  = PERF_COMP_ZSTD;
@@ -1624,6 +1618,14 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 	}
 	session->header.env.comp_mmap_len = session->evlist->core.mmap_len;
 
+#ifdef HAVE_EVENTFD_SUPPORT
+	err = evlist__add_pollfd(rec->evlist, done_fd);
+	if (err < 0) {
+		pr_err("Failed to add wakeup eventfd to poll list\n");
+		goto out_child;
+	}
+#endif // HAVE_EVENTFD_SUPPORT
+
 	if (rec->opts.kcore) {
 		err = record__kcore_copy(&session->machines.host, data);
 		if (err) {
-- 
2.25.4