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    Subject[RFD 2/5] tracing: Add support to sort on the key
    Date
    The hist patch allows sorting on values only. By allowing to
    sort also on the key we can do something like this:

    'hist:key=latency:val=hitcount:sort=latency'

    latency: 16 hitcount: 3
    latency: 17 hitcount: 171
    latency: 18 hitcount: 626
    latency: 19 hitcount: 594
    latency: 20 hitcount: 306
    latency: 21 hitcount: 214
    latency: 22 hitcount: 232
    latency: 23 hitcount: 283
    latency: 24 hitcount: 235
    latency: 25 hitcount: 105
    latency: 26 hitcount: 54
    latency: 27 hitcount: 79
    latency: 28 hitcount: 214
    latency: 29 hitcount: 895
    latency: 30 hitcount: 1400
    latency: 31 hitcount: 774
    latency: 32 hitcount: 653
    [...]

    The obvious choice for the bool was already taken. I haven't found a
    good name for the the flag. I guess it would make sense to refactor the
    sorting code so that it doesn't really matter what kind of field it
    is.

    BTW, I wonder if it would possible to drop the need to always provide
    the 'val' argument and just assume the 'val=hitcount' in this case.

    Not for inclusion!

    Not-Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
    ---
    kernel/trace/trace_events_hist.c | 35 +++++++++++++++++++++++++++++++----
    1 file changed, 31 insertions(+), 4 deletions(-)

    diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
    index 9a7a675..fe06707 100644
    --- a/kernel/trace/trace_events_hist.c
    +++ b/kernel/trace/trace_events_hist.c
    @@ -89,6 +89,7 @@ enum hist_field_flags {
    struct hist_trigger_sort_key {
    bool use_hitcount;
    bool use_key;
    + bool use_real_key;
    bool descending;
    unsigned int idx;
    };
    @@ -260,7 +261,7 @@ static void destroy_hist_fields(struct hist_trigger_data *hist_data)
    }
    }

    -static inline struct hist_trigger_sort_key *create_default_sort_key(void)
    +static inline struct hist_trigger_sort_key *create_hitcount_sort_key(void)
    {
    struct hist_trigger_sort_key *sort_key;

    @@ -273,6 +274,19 @@ static inline struct hist_trigger_sort_key *create_default_sort_key(void)
    return sort_key;
    }

    +static inline struct hist_trigger_sort_key *create_real_key_sort_key(void)
    +{
    + struct hist_trigger_sort_key *sort_key;
    +
    + sort_key = kzalloc(sizeof(*sort_key), GFP_KERNEL);
    + if (!sort_key)
    + return ERR_PTR(-ENOMEM);
    +
    + sort_key->use_real_key = true;
    +
    + return sort_key;
    +}
    +
    static inline struct hist_trigger_sort_key *
    create_sort_key(char *field_name, struct hist_trigger_data *hist_data)
    {
    @@ -280,7 +294,10 @@ create_sort_key(char *field_name, struct hist_trigger_data *hist_data)
    unsigned int i;

    if (!strcmp(field_name, "hitcount"))
    - return create_default_sort_key();
    + return create_hitcount_sort_key();
    +
    + if (!strcmp(field_name, hist_data->key->field->name))
    + return create_real_key_sort_key();

    for (i = 0; i < hist_data->n_vals; i++)
    if (!strcmp(field_name, hist_data->vals[i]->field->name))
    @@ -306,7 +323,7 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
    int ret = 0;

    if (!fields_str) {
    - sort_key = create_default_sort_key();
    + sort_key = create_hitcount_sort_key();
    if (IS_ERR(sort_key)) {
    ret = PTR_ERR(sort_key);
    goto out;
    @@ -984,6 +1001,12 @@ static int cmp_entries(const struct hist_trigger_sort_entry **a,
    hist_data = entry_a->hist_data;
    sort_key = hist_data->sort_key_cur;

    + if (sort_key->use_real_key) {
    + val_a = *(u64 *)entry_a->key;
    + val_b = *(u64 *)entry_b->key;
    + goto out;
    + }
    +
    if (sort_key->use_key) {
    if (memcmp((*a)->key, (*b)->key, hist_data->map->key_size))
    ret = 1;
    @@ -998,6 +1021,7 @@ static int cmp_entries(const struct hist_trigger_sort_entry **a,
    val_b = atomic64_read(&entry_b->sums[sort_key->idx]);
    }

    +out:
    if (val_a > val_b)
    ret = 1;
    else if (val_a < val_b)
    @@ -1372,7 +1396,10 @@ static int event_hist_trigger_print(struct seq_file *m,
    else {
    unsigned int idx = hist_data->sort_keys[i]->idx;

    - hist_field_print(m, hist_data->vals[idx]);
    + if (hist_data->sort_keys[i]->use_real_key)
    + hist_field_print(m, hist_data->key);
    + else
    + hist_field_print(m, hist_data->vals[idx]);
    }
    }

    --
    2.1.0


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