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tracing: Dynamically allocate the per-elt hist_elt_data array

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Setting the hist_elt_data.field_var_str[] array unconditionally to a
size of SYNTH_FIELD_MAX elements wastes space unnecessarily.  The
actual number of elements needed can be calculated at run-time
instead.

In most cases, this will save a lot of space since it's a per-elt
array which isn't normally close to being full.  It also allows us to
increase SYNTH_FIELD_MAX without worrying about even more wastage when
we do that.

Link: https://lkml.kernel.org/r/d52ae0ad5e1b59af7c4f54faf3fc098461fd82b3.camel@kernel.org

Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Tested-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Tom Zanussi 2021-09-02 15:57:12 -05:00 committed by Steven Rostedt (VMware)
parent 0be083cee4
commit c910db943d
1 changed files with 12 additions and 2 deletions
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14
kernel/trace/trace_events_hist.c
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@ -508,7 +508,8 @@ struct track_data {
struct hist_elt_data {
char *comm;
u64 *var_ref_vals;
char *field_var_str[SYNTH_FIELDS_MAX];
char **field_var_str;
int n_field_var_str;
};
struct snapshot_context {
@ -1401,9 +1402,11 @@ static void hist_elt_data_free(struct hist_elt_data *elt_data)
{
unsigned int i;
for (i = 0; i < SYNTH_FIELDS_MAX; i++)
for (i = 0; i < elt_data->n_field_var_str; i++)
kfree(elt_data->field_var_str[i]);
kfree(elt_data->field_var_str);
kfree(elt_data->comm);
kfree(elt_data);
}
@ -1451,6 +1454,13 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
size = STR_VAR_LEN_MAX;
elt_data->field_var_str = kcalloc(n_str, sizeof(char *), GFP_KERNEL);
if (!elt_data->field_var_str) {
hist_elt_data_free(elt_data);
return -EINVAL;
}
elt_data->n_field_var_str = n_str;
for (i = 0; i < n_str; i++) {
elt_data->field_var_str[i] = kzalloc(size, GFP_KERNEL);
if (!elt_data->field_var_str[i]) {