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    Subject[PATCH 2/2] perf evlist: Fix per thread mmap setup
    Date
    From: Arnaldo Carvalho de Melo <acme@redhat.com>

    The PERF_EVENT_IOC_SET_OUTPUT ioctl was returning -EINVAL when using
    --pid when monitoring multithreaded apps, as we can only share a ring
    buffer for events on the same thread if not doing per cpu.

    Fix it by using per thread ring buffers.

    Tested with:

    [root@felicio ~]# tuna -t 26131 -CP | nl
    1 thread ctxt_switches
    2 pid SCHED_ rtpri affinity voluntary nonvoluntary cmd
    3 26131 OTHER 0 0,1 10814276 2397830 chromium-browse
    4 642 OTHER 0 0,1 14688 0 chromium-browse
    5 26148 OTHER 0 0,1 713602 115479 chromium-browse
    6 26149 OTHER 0 0,1 801958 2262 chromium-browse
    7 26150 OTHER 0 0,1 1271128 248 chromium-browse
    8 26151 OTHER 0 0,1 3 0 chromium-browse
    9 27049 OTHER 0 0,1 36796 9 chromium-browse
    10 618 OTHER 0 0,1 14711 0 chromium-browse
    11 661 OTHER 0 0,1 14593 0 chromium-browse
    12 29048 OTHER 0 0,1 28125 0 chromium-browse
    13 26143 OTHER 0 0,1 2202789 781 chromium-browse
    [root@felicio ~]#

    So 11 threads under pid 26131, then:

    [root@felicio ~]# perf record -F 50000 --pid 26131

    [root@felicio ~]# grep perf_event /proc/`pidof perf`/maps | nl
    1 7fa4a2538000-7fa4a25b9000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    2 7fa4a25b9000-7fa4a263a000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    3 7fa4a263a000-7fa4a26bb000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    4 7fa4a26bb000-7fa4a273c000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    5 7fa4a273c000-7fa4a27bd000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    6 7fa4a27bd000-7fa4a283e000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    7 7fa4a283e000-7fa4a28bf000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    8 7fa4a28bf000-7fa4a2940000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    9 7fa4a2940000-7fa4a29c1000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    10 7fa4a29c1000-7fa4a2a42000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    11 7fa4a2a42000-7fa4a2ac3000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    [root@felicio ~]#

    11 mmaps, one per thread since we didn't specify any CPU list, so we need one
    mmap per thread and:

    [root@felicio ~]# perf record -F 50000 --pid 26131
    ^M
    ^C[ perf record: Woken up 79 times to write data ]
    [ perf record: Captured and wrote 20.614 MB perf.data (~900639 samples) ]

    [root@felicio ~]# perf report -D | grep PERF_RECORD_SAMPLE | cut -d/ -f2 | cut -d: -f1 | sort -n | uniq -c | sort -nr | nl
    1 371310 26131
    2 96516 26148
    3 95694 26149
    4 95203 26150
    5 7291 26143
    6 87 27049
    7 76 661
    8 60 29048
    9 47 618
    10 43 642
    [root@felicio ~]#

    Ok, one of the threads, 26151 was quiescent, so no samples there, but all the
    others are there.

    Then, if I specify one CPU:

    [root@felicio ~]# perf record -F 50000 --pid 26131 --cpu 1
    ^C[ perf record: Woken up 1 times to write data ]
    [ perf record: Captured and wrote 0.680 MB perf.data (~29730 samples) ]

    [root@felicio ~]# perf report -D | grep PERF_RECORD_SAMPLE | cut -d/ -f2 | cut -d: -f1 | sort -n | uniq -c | sort -nr | nl
    1 8444 26131
    2 2584 26149
    3 2518 26148
    4 2324 26150
    5 123 26143
    6 9 661
    7 9 29048
    [root@felicio ~]#

    This machine has two cores, so fewer threads appeared on the radar, and:

    [root@felicio ~]# grep perf_event /proc/`pidof perf`/maps | nl
    1 7f484b922000-7f484b9a3000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    [root@felicio ~]#

    Just one mmap, as now we can use just one per-cpu buffer instead of the
    per-thread needed in the previous case.

    For global profiling:

    [root@felicio ~]# perf record -F 50000 -a
    ^C[ perf record: Woken up 26 times to write data ]
    [ perf record: Captured and wrote 7.128 MB perf.data (~311412 samples) ]

    [root@felicio ~]# grep perf_event /proc/`pidof perf`/maps | nl
    1 7fb49b435000-7fb49b4b6000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    2 7fb49b4b6000-7fb49b537000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    [root@felicio ~]#

    It uses per-cpu buffers.

    For just one thread:

    [root@felicio ~]# perf record -F 50000 --tid 26148
    ^C[ perf record: Woken up 2 times to write data ]
    [ perf record: Captured and wrote 0.330 MB perf.data (~14426 samples) ]

    [root@felicio ~]# perf report -D | grep PERF_RECORD_SAMPLE | cut -d/ -f2 | cut -d: -f1 | sort -n | uniq -c | sort -nr | nl
    1 9969 26148
    [root@felicio ~]#

    [root@felicio ~]# grep perf_event /proc/`pidof perf`/maps | nl
    1 7f286a51b000-7f286a59c000 rwxs 00000000 00:09 4064 anon_inode:[perf_event]
    [root@felicio ~]#

    Tested-by: David Ahern <dsahern@gmail.com>
    Tested-by: Lin Ming <ming.m.lin@intel.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Mike Galbraith <efault@gmx.de>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Stephane Eranian <eranian@google.com>
    Cc: Tom Zanussi <tzanussi@gmail.com>
    Link: http://lkml.kernel.org/r/20110426204401.GB1746@ghostprotocols.net
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    ---
    tools/perf/builtin-record.c | 2 +-
    tools/perf/builtin-test.c | 2 +-
    tools/perf/builtin-top.c | 8 +-
    tools/perf/util/evlist.c | 151 ++++++++++++++++++++++++++++++-------------
    tools/perf/util/evlist.h | 3 +-
    tools/perf/util/python.c | 2 +-
    6 files changed, 115 insertions(+), 53 deletions(-)

    diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
    index 4165382..0974f95 100644
    --- a/tools/perf/builtin-record.c
    +++ b/tools/perf/builtin-record.c
    @@ -427,7 +427,7 @@ static void mmap_read_all(void)
    {
    int i;

    - for (i = 0; i < evsel_list->cpus->nr; i++) {
    + for (i = 0; i < evsel_list->nr_mmaps; i++) {
    if (evsel_list->mmap[i].base)
    mmap_read(&evsel_list->mmap[i]);
    }
    diff --git a/tools/perf/builtin-test.c b/tools/perf/builtin-test.c
    index 11e3c84..2f9a337 100644
    --- a/tools/perf/builtin-test.c
    +++ b/tools/perf/builtin-test.c
    @@ -549,7 +549,7 @@ static int test__basic_mmap(void)
    ++foo;
    }

    - while ((event = perf_evlist__read_on_cpu(evlist, 0)) != NULL) {
    + while ((event = perf_evlist__mmap_read(evlist, 0)) != NULL) {
    struct perf_sample sample;

    if (event->header.type != PERF_RECORD_SAMPLE) {
    diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
    index 7e3d6e3..ebfc7cf 100644
    --- a/tools/perf/builtin-top.c
    +++ b/tools/perf/builtin-top.c
    @@ -801,12 +801,12 @@ static void perf_event__process_sample(const union perf_event *event,
    }
    }

    -static void perf_session__mmap_read_cpu(struct perf_session *self, int cpu)
    +static void perf_session__mmap_read_idx(struct perf_session *self, int idx)
    {
    struct perf_sample sample;
    union perf_event *event;

    - while ((event = perf_evlist__read_on_cpu(top.evlist, cpu)) != NULL) {
    + while ((event = perf_evlist__mmap_read(top.evlist, idx)) != NULL) {
    perf_session__parse_sample(self, event, &sample);

    if (event->header.type == PERF_RECORD_SAMPLE)
    @@ -820,8 +820,8 @@ static void perf_session__mmap_read(struct perf_session *self)
    {
    int i;

    - for (i = 0; i < top.evlist->cpus->nr; i++)
    - perf_session__mmap_read_cpu(self, i);
    + for (i = 0; i < top.evlist->nr_mmaps; i++)
    + perf_session__mmap_read_idx(self, i);
    }

    static void start_counters(struct perf_evlist *evlist)
    diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
    index 1884a7c..23eb22b 100644
    --- a/tools/perf/util/evlist.c
    +++ b/tools/perf/util/evlist.c
    @@ -166,11 +166,11 @@ struct perf_evsel *perf_evlist__id2evsel(struct perf_evlist *evlist, u64 id)
    return NULL;
    }

    -union perf_event *perf_evlist__read_on_cpu(struct perf_evlist *evlist, int cpu)
    +union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
    {
    /* XXX Move this to perf.c, making it generally available */
    unsigned int page_size = sysconf(_SC_PAGE_SIZE);
    - struct perf_mmap *md = &evlist->mmap[cpu];
    + struct perf_mmap *md = &evlist->mmap[idx];
    unsigned int head = perf_mmap__read_head(md);
    unsigned int old = md->prev;
    unsigned char *data = md->base + page_size;
    @@ -235,31 +235,37 @@ union perf_event *perf_evlist__read_on_cpu(struct perf_evlist *evlist, int cpu)

    void perf_evlist__munmap(struct perf_evlist *evlist)
    {
    - int cpu;
    + int i;

    - for (cpu = 0; cpu < evlist->cpus->nr; cpu++) {
    - if (evlist->mmap[cpu].base != NULL) {
    - munmap(evlist->mmap[cpu].base, evlist->mmap_len);
    - evlist->mmap[cpu].base = NULL;
    + for (i = 0; i < evlist->nr_mmaps; i++) {
    + if (evlist->mmap[i].base != NULL) {
    + munmap(evlist->mmap[i].base, evlist->mmap_len);
    + evlist->mmap[i].base = NULL;
    }
    }
    +
    + free(evlist->mmap);
    + evlist->mmap = NULL;
    }

    int perf_evlist__alloc_mmap(struct perf_evlist *evlist)
    {
    - evlist->mmap = zalloc(evlist->cpus->nr * sizeof(struct perf_mmap));
    + evlist->nr_mmaps = evlist->cpus->nr;
    + if (evlist->cpus->map[0] == -1)
    + evlist->nr_mmaps = evlist->threads->nr;
    + evlist->mmap = zalloc(evlist->nr_mmaps * sizeof(struct perf_mmap));
    return evlist->mmap != NULL ? 0 : -ENOMEM;
    }

    static int __perf_evlist__mmap(struct perf_evlist *evlist, struct perf_evsel *evsel,
    - int cpu, int prot, int mask, int fd)
    + int idx, int prot, int mask, int fd)
    {
    - evlist->mmap[cpu].prev = 0;
    - evlist->mmap[cpu].mask = mask;
    - evlist->mmap[cpu].base = mmap(NULL, evlist->mmap_len, prot,
    + evlist->mmap[idx].prev = 0;
    + evlist->mmap[idx].mask = mask;
    + evlist->mmap[idx].base = mmap(NULL, evlist->mmap_len, prot,
    MAP_SHARED, fd, 0);
    - if (evlist->mmap[cpu].base == MAP_FAILED) {
    - if (evlist->cpus->map[cpu] == -1 && evsel->attr.inherit)
    + if (evlist->mmap[idx].base == MAP_FAILED) {
    + if (evlist->cpus->map[idx] == -1 && evsel->attr.inherit)
    ui__warning("Inherit is not allowed on per-task "
    "events using mmap.\n");
    return -1;
    @@ -269,6 +275,86 @@ static int __perf_evlist__mmap(struct perf_evlist *evlist, struct perf_evsel *ev
    return 0;
    }

    +static int perf_evlist__mmap_per_cpu(struct perf_evlist *evlist, int prot, int mask)
    +{
    + struct perf_evsel *evsel;
    + int cpu, thread;
    +
    + for (cpu = 0; cpu < evlist->cpus->nr; cpu++) {
    + int output = -1;
    +
    + for (thread = 0; thread < evlist->threads->nr; thread++) {
    + list_for_each_entry(evsel, &evlist->entries, node) {
    + int fd = FD(evsel, cpu, thread);
    +
    + if (output == -1) {
    + output = fd;
    + if (__perf_evlist__mmap(evlist, evsel, cpu,
    + prot, mask, output) < 0)
    + goto out_unmap;
    + } else {
    + if (ioctl(fd, PERF_EVENT_IOC_SET_OUTPUT, output) != 0)
    + goto out_unmap;
    + }
    +
    + if ((evsel->attr.read_format & PERF_FORMAT_ID) &&
    + perf_evlist__id_add_fd(evlist, evsel, cpu, thread, fd) < 0)
    + goto out_unmap;
    + }
    + }
    + }
    +
    + return 0;
    +
    +out_unmap:
    + for (cpu = 0; cpu < evlist->cpus->nr; cpu++) {
    + if (evlist->mmap[cpu].base != NULL) {
    + munmap(evlist->mmap[cpu].base, evlist->mmap_len);
    + evlist->mmap[cpu].base = NULL;
    + }
    + }
    + return -1;
    +}
    +
    +static int perf_evlist__mmap_per_thread(struct perf_evlist *evlist, int prot, int mask)
    +{
    + struct perf_evsel *evsel;
    + int thread;
    +
    + for (thread = 0; thread < evlist->threads->nr; thread++) {
    + int output = -1;
    +
    + list_for_each_entry(evsel, &evlist->entries, node) {
    + int fd = FD(evsel, 0, thread);
    +
    + if (output == -1) {
    + output = fd;
    + if (__perf_evlist__mmap(evlist, evsel, thread,
    + prot, mask, output) < 0)
    + goto out_unmap;
    + } else {
    + if (ioctl(fd, PERF_EVENT_IOC_SET_OUTPUT, output) != 0)
    + goto out_unmap;
    + }
    +
    + if ((evsel->attr.read_format & PERF_FORMAT_ID) &&
    + perf_evlist__id_add_fd(evlist, evsel, 0, thread, fd) < 0)
    + goto out_unmap;
    + }
    + }
    +
    + return 0;
    +
    +out_unmap:
    + for (thread = 0; thread < evlist->threads->nr; thread++) {
    + if (evlist->mmap[thread].base != NULL) {
    + munmap(evlist->mmap[thread].base, evlist->mmap_len);
    + evlist->mmap[thread].base = NULL;
    + }
    + }
    + return -1;
    +}
    +
    /** perf_evlist__mmap - Create per cpu maps to receive events
    *
    * @evlist - list of events
    @@ -287,11 +373,11 @@ static int __perf_evlist__mmap(struct perf_evlist *evlist, struct perf_evsel *ev
    int perf_evlist__mmap(struct perf_evlist *evlist, int pages, bool overwrite)
    {
    unsigned int page_size = sysconf(_SC_PAGE_SIZE);
    - int mask = pages * page_size - 1, cpu;
    - struct perf_evsel *first_evsel, *evsel;
    + int mask = pages * page_size - 1;
    + struct perf_evsel *evsel;
    const struct cpu_map *cpus = evlist->cpus;
    const struct thread_map *threads = evlist->threads;
    - int thread, prot = PROT_READ | (overwrite ? 0 : PROT_WRITE);
    + int prot = PROT_READ | (overwrite ? 0 : PROT_WRITE);

    if (evlist->mmap == NULL && perf_evlist__alloc_mmap(evlist) < 0)
    return -ENOMEM;
    @@ -301,43 +387,18 @@ int perf_evlist__mmap(struct perf_evlist *evlist, int pages, bool overwrite)

    evlist->overwrite = overwrite;
    evlist->mmap_len = (pages + 1) * page_size;
    - first_evsel = list_entry(evlist->entries.next, struct perf_evsel, node);

    list_for_each_entry(evsel, &evlist->entries, node) {
    if ((evsel->attr.read_format & PERF_FORMAT_ID) &&
    evsel->sample_id == NULL &&
    perf_evsel__alloc_id(evsel, cpus->nr, threads->nr) < 0)
    return -ENOMEM;
    -
    - for (cpu = 0; cpu < cpus->nr; cpu++) {
    - for (thread = 0; thread < threads->nr; thread++) {
    - int fd = FD(evsel, cpu, thread);
    -
    - if (evsel->idx || thread) {
    - if (ioctl(fd, PERF_EVENT_IOC_SET_OUTPUT,
    - FD(first_evsel, cpu, 0)) != 0)
    - goto out_unmap;
    - } else if (__perf_evlist__mmap(evlist, evsel, cpu,
    - prot, mask, fd) < 0)
    - goto out_unmap;
    -
    - if ((evsel->attr.read_format & PERF_FORMAT_ID) &&
    - perf_evlist__id_add_fd(evlist, evsel, cpu, thread, fd) < 0)
    - goto out_unmap;
    - }
    - }
    }

    - return 0;
    + if (evlist->cpus->map[0] == -1)
    + return perf_evlist__mmap_per_thread(evlist, prot, mask);

    -out_unmap:
    - for (cpu = 0; cpu < cpus->nr; cpu++) {
    - if (evlist->mmap[cpu].base != NULL) {
    - munmap(evlist->mmap[cpu].base, evlist->mmap_len);
    - evlist->mmap[cpu].base = NULL;
    - }
    - }
    - return -1;
    + return perf_evlist__mmap_per_cpu(evlist, prot, mask);
    }

    int perf_evlist__create_maps(struct perf_evlist *evlist, pid_t target_pid,
    diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
    index 8b1cb7a..7109d7a 100644
    --- a/tools/perf/util/evlist.h
    +++ b/tools/perf/util/evlist.h
    @@ -17,6 +17,7 @@ struct perf_evlist {
    struct hlist_head heads[PERF_EVLIST__HLIST_SIZE];
    int nr_entries;
    int nr_fds;
    + int nr_mmaps;
    int mmap_len;
    bool overwrite;
    union perf_event event_copy;
    @@ -46,7 +47,7 @@ void perf_evlist__add_pollfd(struct perf_evlist *evlist, int fd);

    struct perf_evsel *perf_evlist__id2evsel(struct perf_evlist *evlist, u64 id);

    -union perf_event *perf_evlist__read_on_cpu(struct perf_evlist *self, int cpu);
    +union perf_event *perf_evlist__mmap_read(struct perf_evlist *self, int idx);

    int perf_evlist__alloc_mmap(struct perf_evlist *evlist);
    int perf_evlist__mmap(struct perf_evlist *evlist, int pages, bool overwrite);
    diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c
    index f5e3845..99c7226 100644
    --- a/tools/perf/util/python.c
    +++ b/tools/perf/util/python.c
    @@ -680,7 +680,7 @@ static PyObject *pyrf_evlist__read_on_cpu(struct pyrf_evlist *pevlist,
    &cpu, &sample_id_all))
    return NULL;

    - event = perf_evlist__read_on_cpu(evlist, cpu);
    + event = perf_evlist__mmap_read(evlist, cpu);
    if (event != NULL) {
    struct perf_evsel *first;
    PyObject *pyevent = pyrf_event__new(event);
    --
    1.6.2.5


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