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    Subject[PATCH 29/44] perf tools: Add AUX area tracing Snapshot Mode
    Date
    Add support for making snapshots of
    AUX area tracing data.

    Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
    ---
    tools/perf/perf.h | 3 ++
    tools/perf/util/auxtrace.c | 85 ++++++++++++++++++++++++++++++++++++++++------
    tools/perf/util/auxtrace.h | 41 ++++++++++++++++++++++
    3 files changed, 119 insertions(+), 10 deletions(-)

    diff --git a/tools/perf/perf.h b/tools/perf/perf.h
    index 5042093..aa79fb8 100644
    --- a/tools/perf/perf.h
    +++ b/tools/perf/perf.h
    @@ -55,6 +55,7 @@ struct record_opts {
    bool sample_intr_regs;
    bool running_time;
    bool full_auxtrace;
    + bool auxtrace_snapshot_mode;
    unsigned int freq;
    unsigned int mmap_pages;
    unsigned int auxtrace_mmap_pages;
    @@ -62,6 +63,8 @@ struct record_opts {
    u64 branch_stack;
    u64 default_interval;
    u64 user_interval;
    + size_t auxtrace_snapshot_size;
    + const char *auxtrace_snapshot_opts;
    bool sample_transaction;
    unsigned initial_delay;
    bool use_clockid;
    diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c
    index b591a9b..4373f97 100644
    --- a/tools/perf/util/auxtrace.c
    +++ b/tools/perf/util/auxtrace.c
    @@ -504,6 +504,29 @@ void auxtrace_record__free(struct auxtrace_record *itr)
    itr->free(itr);
    }

    +int auxtrace_record__snapshot_start(struct auxtrace_record *itr)
    +{
    + if (itr && itr->snapshot_start)
    + return itr->snapshot_start(itr);
    + return 0;
    +}
    +
    +int auxtrace_record__snapshot_finish(struct auxtrace_record *itr)
    +{
    + if (itr && itr->snapshot_finish)
    + return itr->snapshot_finish(itr);
    + return 0;
    +}
    +
    +int auxtrace_record__find_snapshot(struct auxtrace_record *itr, int idx,
    + struct auxtrace_mmap *mm,
    + unsigned char *data, u64 *head, u64 *old)
    +{
    + if (itr && itr->find_snapshot)
    + return itr->find_snapshot(itr, idx, mm, data, head, old);
    + return 0;
    +}
    +
    int auxtrace_record__options(struct auxtrace_record *itr,
    struct perf_evlist *evlist,
    struct record_opts *opts)
    @@ -520,6 +543,19 @@ u64 auxtrace_record__reference(struct auxtrace_record *itr)
    return 0;
    }

    +int auxtrace_parse_snapshot_options(struct auxtrace_record *itr,
    + struct record_opts *opts, const char *str)
    +{
    + if (!str)
    + return 0;
    +
    + if (itr)
    + return itr->parse_snapshot_options(itr, opts, str);
    +
    + pr_err("No AUX area tracing to snapshot\n");
    + return -EINVAL;
    +}
    +
    struct auxtrace_record *__weak
    auxtrace_record__init(struct perf_evlist *evlist __maybe_unused, int *err)
    {
    @@ -1073,16 +1109,26 @@ int perf_event__process_auxtrace_error(struct perf_tool *tool __maybe_unused,
    return 0;
    }

    -int auxtrace_mmap__read(struct auxtrace_mmap *mm, struct auxtrace_record *itr,
    - struct perf_tool *tool, process_auxtrace_t fn)
    +static int __auxtrace_mmap__read(struct auxtrace_mmap *mm,
    + struct auxtrace_record *itr,
    + struct perf_tool *tool, process_auxtrace_t fn,
    + bool snapshot, size_t snapshot_size)
    {
    - u64 head = auxtrace_mmap__read_head(mm);
    - u64 old = mm->prev, offset, ref;
    + u64 head, old = mm->prev, offset, ref;
    unsigned char *data = mm->base;
    size_t size, head_off, old_off, len1, len2, padding;
    union perf_event ev;
    void *data1, *data2;

    + if (snapshot) {
    + head = auxtrace_mmap__read_snapshot_head(mm);
    + if (auxtrace_record__find_snapshot(itr, mm->idx, mm, data, &head,
    + &old))
    + return -1;
    + } else {
    + head = auxtrace_mmap__read_head(mm);
    + }
    +
    if (old == head)
    return 0;

    @@ -1102,6 +1148,9 @@ int auxtrace_mmap__read(struct auxtrace_mmap *mm, struct auxtrace_record *itr,
    else
    size = mm->len - (old_off - head_off);

    + if (snapshot && size > snapshot_size)
    + size = snapshot_size;
    +
    ref = auxtrace_record__reference(itr);

    if (head > old || size <= head || mm->mask) {
    @@ -1149,18 +1198,34 @@ int auxtrace_mmap__read(struct auxtrace_mmap *mm, struct auxtrace_record *itr,

    mm->prev = head;

    - auxtrace_mmap__write_tail(mm, head);
    - if (itr->read_finish) {
    - int err;
    + if (!snapshot) {
    + auxtrace_mmap__write_tail(mm, head);
    + if (itr->read_finish) {
    + int err;

    - err = itr->read_finish(itr, mm->idx);
    - if (err < 0)
    - return err;
    + err = itr->read_finish(itr, mm->idx);
    + if (err < 0)
    + return err;
    + }
    }

    return 1;
    }

    +int auxtrace_mmap__read(struct auxtrace_mmap *mm, struct auxtrace_record *itr,
    + struct perf_tool *tool, process_auxtrace_t fn)
    +{
    + return __auxtrace_mmap__read(mm, itr, tool, fn, false, 0);
    +}
    +
    +int auxtrace_mmap__read_snapshot(struct auxtrace_mmap *mm,
    + struct auxtrace_record *itr,
    + struct perf_tool *tool, process_auxtrace_t fn,
    + size_t snapshot_size)
    +{
    + return __auxtrace_mmap__read(mm, itr, tool, fn, true, snapshot_size);
    +}
    +
    /**
    * struct auxtrace_cache - hash table to implement a cache
    * @hashtable: the hashtable
    diff --git a/tools/perf/util/auxtrace.h b/tools/perf/util/auxtrace.h
    index 8c6cbb1..f0bacb6 100644
    --- a/tools/perf/util/auxtrace.h
    +++ b/tools/perf/util/auxtrace.h
    @@ -276,6 +276,10 @@ struct auxtrace_mmap_params {
    * @info_priv_size: return the size of the private data in auxtrace_info_event
    * @info_fill: fill-in the private data in auxtrace_info_event
    * @free: free this auxtrace record structure
    + * @snapshot_start: starting a snapshot
    + * @snapshot_finish: finishing a snapshot
    + * @find_snapshot: find data to snapshot within auxtrace mmap
    + * @parse_snapshot_options: parse snapshot options
    * @reference: provide a 64-bit reference number for auxtrace_event
    * @read_finish: called after reading from an auxtrace mmap
    */
    @@ -289,12 +293,36 @@ struct auxtrace_record {
    struct auxtrace_info_event *auxtrace_info,
    size_t priv_size);
    void (*free)(struct auxtrace_record *itr);
    + int (*snapshot_start)(struct auxtrace_record *itr);
    + int (*snapshot_finish)(struct auxtrace_record *itr);
    + int (*find_snapshot)(struct auxtrace_record *itr, int idx,
    + struct auxtrace_mmap *mm, unsigned char *data,
    + u64 *head, u64 *old);
    + int (*parse_snapshot_options)(struct auxtrace_record *itr,
    + struct record_opts *opts,
    + const char *str);
    u64 (*reference)(struct auxtrace_record *itr);
    int (*read_finish)(struct auxtrace_record *itr, int idx);
    };

    #ifdef HAVE_AUXTRACE_SUPPORT

    +/*
    + * In snapshot mode the mmapped page is read-only which makes using
    + * __sync_val_compare_and_swap() problematic. However, snapshot mode expects
    + * the buffer is not updated while the snapshot is made (e.g. Intel PT disables
    + * the event) so there is not a race anyway.
    + */
    +static inline u64 auxtrace_mmap__read_snapshot_head(struct auxtrace_mmap *mm)
    +{
    + struct perf_event_mmap_page *pc = mm->userpg;
    + u64 head = ACCESS_ONCE(pc->aux_head);
    +
    + /* Ensure all reads are done after we read the head */
    + rmb();
    + return head;
    +}
    +
    static inline u64 auxtrace_mmap__read_head(struct auxtrace_mmap *mm)
    {
    struct perf_event_mmap_page *pc = mm->userpg;
    @@ -346,6 +374,11 @@ typedef int (*process_auxtrace_t)(struct perf_tool *tool,
    int auxtrace_mmap__read(struct auxtrace_mmap *mm, struct auxtrace_record *itr,
    struct perf_tool *tool, process_auxtrace_t fn);

    +int auxtrace_mmap__read_snapshot(struct auxtrace_mmap *mm,
    + struct auxtrace_record *itr,
    + struct perf_tool *tool, process_auxtrace_t fn,
    + size_t snapshot_size);
    +
    int auxtrace_queues__init(struct auxtrace_queues *queues);
    int auxtrace_queues__add_event(struct auxtrace_queues *queues,
    struct perf_session *session,
    @@ -383,6 +416,9 @@ void *auxtrace_cache__lookup(struct auxtrace_cache *c, u32 key);
    struct auxtrace_record *auxtrace_record__init(struct perf_evlist *evlist,
    int *err);

    +int auxtrace_parse_snapshot_options(struct auxtrace_record *itr,
    + struct record_opts *opts,
    + const char *str);
    int auxtrace_record__options(struct auxtrace_record *itr,
    struct perf_evlist *evlist,
    struct record_opts *opts);
    @@ -392,6 +428,11 @@ int auxtrace_record__info_fill(struct auxtrace_record *itr,
    struct auxtrace_info_event *auxtrace_info,
    size_t priv_size);
    void auxtrace_record__free(struct auxtrace_record *itr);
    +int auxtrace_record__snapshot_start(struct auxtrace_record *itr);
    +int auxtrace_record__snapshot_finish(struct auxtrace_record *itr);
    +int auxtrace_record__find_snapshot(struct auxtrace_record *itr, int idx,
    + struct auxtrace_mmap *mm,
    + unsigned char *data, u64 *head, u64 *old);
    u64 auxtrace_record__reference(struct auxtrace_record *itr);

    int auxtrace_index__auxtrace_event(struct list_head *head, union perf_event *event,
    --
    1.9.1


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