tracing: Have show_event_trigger/filter format a bit more in columns

By doing:

 # trace-cmd sqlhist -e -n futex_wait select TIMESTAMP_DELTA_USECS as lat from sys_enter_futex as start join sys_exit_futex as end on start.common_pid = end.common_pid

and

 # trace-cmd start -e futex_wait -f 'lat > 100' -e page_pool_state_release -f 'pfn == 1'

The output of the show_event_trigger and show_event_filter files are well
aligned because of the inconsistent 'tab' spacing:

 ~# cat /sys/kernel/tracing/show_event_triggers
syscalls:sys_exit_futex	hist:keys=common_pid:vals=hitcount:__lat_12046_2=common_timestamp.usecs-$__arg_12046_1:sort=hitcount:size=2048:clock=global:onmatch(syscalls.sys_enter_futex).trace(futex_wait,$__lat_12046_2) [active]
syscalls:sys_enter_futex	hist:keys=common_pid:vals=hitcount:__arg_12046_1=common_timestamp.usecs:sort=hitcount:size=2048:clock=global [active]

 ~# cat /sys/kernel/tracing/show_event_filters
synthetic:futex_wait	(lat > 100)
page_pool:page_pool_state_release	(pfn == 1)

This makes it not so easy to read. Instead, force the spacing to be at
least 32 bytes from the beginning (one space if the system:event is longer
than 30 bytes):

 ~# cat /sys/kernel/tracing/show_event_triggers
syscalls:sys_exit_futex          hist:keys=common_pid:vals=hitcount:__lat_8125_2=common_timestamp.usecs-$__arg_8125_1:sort=hitcount:size=2048:clock=global:onmatch(syscalls.sys_enter_futex).trace(futex_wait,$__lat_8125_2) [active]
syscalls:sys_enter_futex         hist:keys=common_pid:vals=hitcount:__arg_8125_1=common_timestamp.usecs:sort=hitcount:size=2048:clock=global [active]

 ~# cat /sys/kernel/tracing/show_event_filters
synthetic:futex_wait             (lat > 100)
page_pool:page_pool_state_release (pfn == 1)

Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20260112153408.18373e73@gandalf.local.home
Reviewed-by: Aaron Tomlin <atomlin@atomlin.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 36936697fa2aae17b3d0f74b5ffa68126ad9749e..f372a6374164e46df7476bedc27167da036b25dc 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1662,6 +1662,18 @@ static void t_stop(struct seq_file *m, void *p)
        mutex_unlock(&event_mutex);
 }
 
+static int get_call_len(struct trace_event_call *call)
+{
+       int len;
+
+       /* Get the length of "<system>:<event>" */
+       len = strlen(call->class->system) + 1;
+       len += strlen(trace_event_name(call));
+
+       /* Set the index to 32 bytes to separate event from data */
+       return len >= 32 ? 1 : 32 - len;
+}
+
 /**
  * t_show_filters - seq_file callback to display active event filters
  * @m: The seq_file interface for formatted output
@@ -1676,14 +1688,17 @@ static int t_show_filters(struct seq_file *m, void *v)
        struct trace_event_file *file = v;
        struct trace_event_call *call = file->event_call;
        struct event_filter *filter;
+       int len;
 
        guard(rcu)();
        filter = rcu_dereference(file->filter);
        if (!filter || !filter->filter_string)
                return 0;
 
-       seq_printf(m, "%s:%s\t%s\n", call->class->system,
-                  trace_event_name(call), filter->filter_string);
+       len = get_call_len(call);
+
+       seq_printf(m, "%s:%s%*.s%s\n", call->class->system,
+                  trace_event_name(call), len, "", filter->filter_string);
 
        return 0;
 }
@@ -1702,6 +1717,7 @@ static int t_show_triggers(struct seq_file *m, void *v)
        struct trace_event_file *file = v;
        struct trace_event_call *call = file->event_call;
        struct event_trigger_data *data;
+       int len;
 
        /*
         * The event_mutex is held by t_start(), protecting the
@@ -1710,9 +1726,11 @@ static int t_show_triggers(struct seq_file *m, void *v)
        if (list_empty(&file->triggers))
                return 0;
 
+       len = get_call_len(call);
+
        list_for_each_entry_rcu(data, &file->triggers, list) {
-               seq_printf(m, "%s:%s\t", call->class->system,
-                          trace_event_name(call));
+               seq_printf(m, "%s:%s%*.s", call->class->system,
+                          trace_event_name(call), len, "");
 
                data->cmd_ops->print(m, data);
        }