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    SubjectRe: [PATCH 1/3] tracing: Reduce overhead of module tracepoints
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    On Wed, 2010-03-24 at 10:57 +0800, Li Zefan wrote:
    > Remove the @refcnt argument, because it has side-effects, and
    > arguments with side-effects are not skipped by the jump over
    > disabled instrumentation, so it adds overhead even when the
    > tracepoints are disabled.

    Thanks, I'll get this ready for 34.

    -- Steve

    >
    > Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
    > ---
    > include/linux/module.h | 6 ++----
    > include/trace/events/module.h | 14 +++++++-------
    > kernel/module.c | 3 +--
    > 3 files changed, 10 insertions(+), 13 deletions(-)
    >
    > diff --git a/include/linux/module.h b/include/linux/module.h
    > index 5e869ff..393ec39 100644
    > --- a/include/linux/module.h
    > +++ b/include/linux/module.h
    > @@ -460,8 +460,7 @@ static inline void __module_get(struct module *module)
    > if (module) {
    > preempt_disable();
    > __this_cpu_inc(module->refptr->count);
    > - trace_module_get(module, _THIS_IP_,
    > - __this_cpu_read(module->refptr->count));
    > + trace_module_get(module, _THIS_IP_);
    > preempt_enable();
    > }
    > }
    > @@ -475,8 +474,7 @@ static inline int try_module_get(struct module *module)
    >
    > if (likely(module_is_live(module))) {
    > __this_cpu_inc(module->refptr->count);
    > - trace_module_get(module, _THIS_IP_,
    > - __this_cpu_read(module->refptr->count));
    > + trace_module_get(module, _THIS_IP_);
    > }
    > else
    > ret = 0;
    > diff --git a/include/trace/events/module.h b/include/trace/events/module.h
    > index 4b0f48b..a585f81 100644
    > --- a/include/trace/events/module.h
    > +++ b/include/trace/events/module.h
    > @@ -53,9 +53,9 @@ TRACE_EVENT(module_free,
    >
    > DECLARE_EVENT_CLASS(module_refcnt,
    >
    > - TP_PROTO(struct module *mod, unsigned long ip, int refcnt),
    > + TP_PROTO(struct module *mod, unsigned long ip),
    >
    > - TP_ARGS(mod, ip, refcnt),
    > + TP_ARGS(mod, ip),
    >
    > TP_STRUCT__entry(
    > __field( unsigned long, ip )
    > @@ -65,7 +65,7 @@ DECLARE_EVENT_CLASS(module_refcnt,
    >
    > TP_fast_assign(
    > __entry->ip = ip;
    > - __entry->refcnt = refcnt;
    > + __entry->refcnt = __this_cpu_read(mod->refptr->count);
    > __assign_str(name, mod->name);
    > ),
    >
    > @@ -75,16 +75,16 @@ DECLARE_EVENT_CLASS(module_refcnt,
    >
    > DEFINE_EVENT(module_refcnt, module_get,
    >
    > - TP_PROTO(struct module *mod, unsigned long ip, int refcnt),
    > + TP_PROTO(struct module *mod, unsigned long ip),
    >
    > - TP_ARGS(mod, ip, refcnt)
    > + TP_ARGS(mod, ip)
    > );
    >
    > DEFINE_EVENT(module_refcnt, module_put,
    >
    > - TP_PROTO(struct module *mod, unsigned long ip, int refcnt),
    > + TP_PROTO(struct module *mod, unsigned long ip),
    >
    > - TP_ARGS(mod, ip, refcnt)
    > + TP_ARGS(mod, ip)
    > );
    >
    > TRACE_EVENT(module_request,
    > diff --git a/kernel/module.c b/kernel/module.c
    > index c968d36..21591ad 100644
    > --- a/kernel/module.c
    > +++ b/kernel/module.c
    > @@ -800,8 +800,7 @@ void module_put(struct module *module)
    > preempt_disable();
    > __this_cpu_dec(module->refptr->count);
    >
    > - trace_module_put(module, _RET_IP_,
    > - __this_cpu_read(module->refptr->count));
    > + trace_module_put(module, _RET_IP_);
    > /* Maybe they're waiting for us to drop reference? */
    > if (unlikely(!module_is_live(module)))
    > wake_up_process(module->waiter);




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