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authorSebastian Andrzej Siewior <bigeasy@linutronix.de>2021-01-25 20:45:08 +0100
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2021-02-02 17:02:06 -0500
commit36590c50b2d0729952511129916beeea30d31d81 (patch)
tree6f6a7dec6834401b5c6648c8f053c06b1c499cd9 /kernel/trace/trace_events.c
parentc6358bacdcdb64eb75192a135b66d3d3e57ad2e5 (diff)
tracing: Merge irqflags + preempt counter.
The state of the interrupts (irqflags) and the preemption counter are both passed down to tracing_generic_entry_update(). Only one bit of irqflags is actually required: The on/off state. The complete 32bit of the preemption counter isn't needed. Just whether of the upper bits (softirq, hardirq and NMI) are set and the preemption depth is needed. The irqflags and the preemption counter could be evaluated early and the information stored in an integer `trace_ctx'. tracing_generic_entry_update() would use the upper bits as the TRACE_FLAG_* and the lower 8bit as the disabled-preemption depth (considering that one must be substracted from the counter in one special cases). The actual preemption value is not used except for the tracing record. The `irqflags' variable is mostly used only for the tracing record. An exception here is for instance wakeup_tracer_call() or probe_wakeup_sched_switch() which explicilty disable interrupts and use that `irqflags' to save (and restore) the IRQ state and to record the state. Struct trace_event_buffer has also the `pc' and flags' members which can be replaced with `trace_ctx' since their actual value is not used outside of trace recording. This will reduce tracing_generic_entry_update() to simply assign values to struct trace_entry. The evaluation of the TRACE_FLAG_* bits is moved to _tracing_gen_ctx_flags() which replaces preempt_count() and local_save_flags() invocations. As an example, ftrace_syscall_enter() may invoke: - trace_buffer_lock_reserve() -> … -> tracing_generic_entry_update() - event_trigger_unlock_commit() -> ftrace_trace_stack() -> … -> tracing_generic_entry_update() -> ftrace_trace_userstack() -> … -> tracing_generic_entry_update() In this case the TRACE_FLAG_* bits were evaluated three times. By using the `trace_ctx' they are evaluated once and assigned three times. A build with all tracers enabled on x86-64 with and without the patch: text data bss dec hex filename 21970669 17084168 7639260 46694097 2c87ed1 vmlinux.old 21970293 17084168 7639260 46693721 2c87d59 vmlinux.new text shrank by 379 bytes, data remained constant. Link: https://lkml.kernel.org/r/20210125194511.3924915-2-bigeasy@linutronix.de Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/trace_events.c')
-rw-r--r--kernel/trace/trace_events.c18
1 files changed, 6 insertions, 12 deletions
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index e9d28eeccb7e..20ccce3e4ffb 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -258,22 +258,19 @@ void *trace_event_buffer_reserve(struct trace_event_buffer *fbuffer,
trace_event_ignore_this_pid(trace_file))
return NULL;
- local_save_flags(fbuffer->flags);
- fbuffer->pc = preempt_count();
/*
* If CONFIG_PREEMPTION is enabled, then the tracepoint itself disables
* preemption (adding one to the preempt_count). Since we are
* interested in the preempt_count at the time the tracepoint was
* hit, we need to subtract one to offset the increment.
*/
- if (IS_ENABLED(CONFIG_PREEMPTION))
- fbuffer->pc--;
+ fbuffer->trace_ctx = tracing_gen_ctx_dec();
fbuffer->trace_file = trace_file;
fbuffer->event =
trace_event_buffer_lock_reserve(&fbuffer->buffer, trace_file,
event_call->event.type, len,
- fbuffer->flags, fbuffer->pc);
+ fbuffer->trace_ctx);
if (!fbuffer->event)
return NULL;
@@ -3678,12 +3675,11 @@ function_test_events_call(unsigned long ip, unsigned long parent_ip,
struct trace_buffer *buffer;
struct ring_buffer_event *event;
struct ftrace_entry *entry;
- unsigned long flags;
+ unsigned int trace_ctx;
long disabled;
int cpu;
- int pc;
- pc = preempt_count();
+ trace_ctx = tracing_gen_ctx();
preempt_disable_notrace();
cpu = raw_smp_processor_id();
disabled = atomic_inc_return(&per_cpu(ftrace_test_event_disable, cpu));
@@ -3691,11 +3687,9 @@ function_test_events_call(unsigned long ip, unsigned long parent_ip,
if (disabled != 1)
goto out;
- local_save_flags(flags);
-
event = trace_event_buffer_lock_reserve(&buffer, &event_trace_file,
TRACE_FN, sizeof(*entry),
- flags, pc);
+ trace_ctx);
if (!event)
goto out;
entry = ring_buffer_event_data(event);
@@ -3703,7 +3697,7 @@ function_test_events_call(unsigned long ip, unsigned long parent_ip,
entry->parent_ip = parent_ip;
event_trigger_unlock_commit(&event_trace_file, buffer, event,
- entry, flags, pc);
+ entry, trace_ctx);
out:
atomic_dec(&per_cpu(ftrace_test_event_disable, cpu));
preempt_enable_notrace();