2 files changed, 21 insertions, 0 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4e342d354c12..988a35263fdd 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3872,6 +3872,7 @@ static const char readme_msg[] =
         "\t            .sym-offset display an address as a symbol and offset\n"
         "\t            .execname   display a common_pid as a program name\n"
         "\t            .syscall    display a syscall id as a syscall name\n\n"
+        "\t            .log2       display log2 value rather than raw number\n\n"
         "\t    The 'pause' parameter can be used to pause an existing hist\n"
         "\t    trigger or to start a hist trigger but not log any events\n"
         "\t    until told to do so.  'continue' can be used to start or\n"
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index bdea5603cbde..23df38aab503 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -68,6 +68,13 @@ static u64 hist_field_pstring(struct hist_field *hist_field, void *event)
         return (u64)(unsigned long)*addr;
 }
 
+static u64 hist_field_log2(struct hist_field *hist_field, void *event)
+{
+        u64 val = *(u64 *)(event + hist_field->field->offset);
+
+        return (u64) ilog2(roundup_pow_of_two(val));
+}
+
 #define DEFINE_HIST_FIELD_FN(type)                                      \
 static u64 hist_field_##type(struct hist_field *hist_field, void *event)\
 {                                                                       \
@@ -111,6 +118,7 @@ enum hist_field_flags {
         HIST_FIELD_FL_EXECNAME          = 64,
         HIST_FIELD_FL_SYSCALL           = 128,
         HIST_FIELD_FL_STACKTRACE        = 256,
+        HIST_FIELD_FL_LOG2              = 512,
 };
 
 struct hist_trigger_attrs {
@@ -358,6 +366,11 @@ static struct hist_field *create_hist_field(struct ftrace_event_field *field,
                 goto out;
         }
 
+        if (flags & HIST_FIELD_FL_LOG2) {
+                hist_field->fn = hist_field_log2;
+                goto out;
+        }
+
         if (is_string_field(field)) {
                 flags |= HIST_FIELD_FL_STRING;
 
@@ -522,6 +535,8 @@ static int create_key_field(struct hist_trigger_data *hist_data,
                                 flags |= HIST_FIELD_FL_EXECNAME;
                         else if (strcmp(field_str, "syscall") == 0)
                                 flags |= HIST_FIELD_FL_SYSCALL;
+                        else if (strcmp(field_str, "log2") == 0)
+                                flags |= HIST_FIELD_FL_LOG2;
                         else {
                                 ret = -EINVAL;
                                 goto out;
@@ -980,6 +995,9 @@ hist_trigger_entry_print(struct seq_file *m,
                                                       key + key_field->offset,
                                                       HIST_STACKTRACE_DEPTH);
                         multiline = true;
+                } else if (key_field->flags & HIST_FIELD_FL_LOG2) {
+                        seq_printf(m, "%s: ~ 2^%-2llu", key_field->field->name,
+                                   *(u64 *)(key + key_field->offset));
                 } else if (key_field->flags & HIST_FIELD_FL_STRING) {
                         seq_printf(m, "%s: %-50s", key_field->field->name,
                                    (char *)(key + key_field->offset));
@@ -1112,6 +1130,8 @@ static const char *get_hist_field_flags(struct hist_field *hist_field)
                 flags_str = "execname";
         else if (hist_field->flags & HIST_FIELD_FL_SYSCALL)
                 flags_str = "syscall";
+        else if (hist_field->flags & HIST_FIELD_FL_LOG2)
+                flags_str = "log2";
 
         return flags_str;
 }