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tracepoint: Optimize using static_call()

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Currently the tracepoint site will iterate a vector and issue indirect
calls to however many handlers are registered (ie. the vector is
long).

Using static_call() it is possible to optimize this for the common
case of only having a single handler registered. In this case the
static_call() can directly call this handler. Otherwise, if the vector
is longer than 1, call a function that iterates the whole vector like
the current code.

[peterz: updated to new interface]

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20200818135805.279421092@infradead.org
This commit is contained in:
Steven Rostedt (VMware)
2020-08-18 15:57:52 +02:00
committed by Ingo Molnar
parent a945c8345e
commit d25e37d89d
4 changed files with 94 additions and 36 deletions
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25
kernel/tracepoint.c
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@@ -221,6 +221,20 @@ static void *func_remove(struct tracepoint_func **funcs,
return old;
}
static void tracepoint_update_call(struct tracepoint *tp, struct tracepoint_func *tp_funcs)
{
void *func = tp->iterator;
/* Synthetic events do not have static call sites */
if (!tp->static_call_key)
return;
if (!tp_funcs[1].func)
func = tp_funcs[0].func;
__static_call_update(tp->static_call_key, tp->static_call_tramp, func);
}
/*
* Add the probe function to a tracepoint.
*/
@@ -251,8 +265,9 @@ static int tracepoint_add_func(struct tracepoint *tp,
* include/linux/tracepoint.h using rcu_dereference_sched().
*/
rcu_assign_pointer(tp->funcs, tp_funcs);
if (!static_key_enabled(&tp->key))
static_key_slow_inc(&tp->key);
tracepoint_update_call(tp, tp_funcs);
static_key_enable(&tp->key);
release_probes(old);
return 0;
}
@@ -281,9 +296,11 @@ static int tracepoint_remove_func(struct tracepoint *tp,
if (tp->unregfunc && static_key_enabled(&tp->key))
tp->unregfunc();
if (static_key_enabled(&tp->key))
static_key_slow_dec(&tp->key);
static_key_disable(&tp->key);
} else {
tracepoint_update_call(tp, tp_funcs);
}
rcu_assign_pointer(tp->funcs, tp_funcs);
release_probes(old);
return 0;