Re: [PATCH v7 01/13] tools/libperf: introduce notion of static polled file descriptors

From: Jiri Olsa
Date: Wed Jun 17 2020 - 05:27:18 EST

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On Mon, Jun 15, 2020 at 06:58:04PM +0200, Jiri Olsa wrote:
> 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 ;-)

Friendly reminder.

jirka

>
> 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
>

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