Re: [PATCH v8 3/3] binder: add transaction latency tracer

[Frankie Chang <Frankie.Chang@mediatek.com>]

On Mon, 2020-09-07 at 14:25 +0200, Greg Kroah-Hartman wrote:
> On Mon, Sep 07, 2020 at 08:00:55PM +0800, Frankie Chang wrote:
> > From: "Frankie.Chang" <Frankie.Chang@mediatek.com>
> > 
> > Record start/end timestamp for binder transaction.
> > When transaction is completed or transaction is free,
> > it would be checked if transaction latency over threshold
> > (default 2 sec), if yes, printing related information for tracing.
> > 
> > /* Implement details */
> > - Add latency tracer module to monitor transaction
> >   by attaching to new tracepoints introduced
> >   when transactions are allocated and freed.
> >   The trace_binder_txn_latency_free would not be enabled
> >   by default. Monitoring which transaction is too slow to
> >   cause some of exceptions is important. So we hook the
> >   tracepoint to call the monitor function.
> > 
> > - Since some of modules would trigger timeout NE
> >   if their binder transaction don't finish in time,
> >   such as audio timeout (5 sec), even BT command
> >   timeout (2 sec), etc.
> >   Therefore, setting the timeout threshold as default
> >   2 seconds could be helpful to debug.
> >   But this timeout threshold is configurable, to let
> >   all users determine the more suitable threshold.
> > 
> > - The reason why printing the related information to
> >   kernel information log but not trace buffer is that
> >   some abnormal transactions may be pending for a long
> >   time ago, they could not be recorded due to buffer
> >   limited.
> > 
> > Signed-off-by: Frankie.Chang <Frankie.Chang@mediatek.com>
> > Acked-by: Todd Kjos <tkjos@google.com>
> > ---
> >  drivers/android/Kconfig                 |    8 +++
> >  drivers/android/Makefile                |    1 +
> >  drivers/android/binder.c                |    6 ++
> >  drivers/android/binder_internal.h       |   13 ++++
> >  drivers/android/binder_latency_tracer.c |  112 +++++++++++++++++++++++++++++++
> >  drivers/android/binder_trace.h          |   26 ++++++-
> >  6 files changed, 163 insertions(+), 3 deletions(-)
> >  create mode 100644 drivers/android/binder_latency_tracer.c
> > 
> > diff --git a/drivers/android/Kconfig b/drivers/android/Kconfig
> > index 53b22e2..8aadaf4 100644
> > --- a/drivers/android/Kconfig
> > +++ b/drivers/android/Kconfig
> > @@ -54,6 +54,14 @@ config ANDROID_BINDER_IPC_SELFTEST
> >  	  exhaustively with combinations of various buffer sizes and
> >  	  alignments.
> >  
> > +config BINDER_TRANSACTION_LATENCY_TRACKING
> > +	tristate "Android Binder transaction tracking"
> > +	help
> > +	  Used for track abnormal binder transaction which is over threshold,
> > +	  when the transaction is done or be free, this transaction would be
> > +	  checked whether it executed overtime.
> > +	  If yes, printing out the detailed info.
> > +
> >  endif # if ANDROID
> >  
> >  endmenu
> > diff --git a/drivers/android/Makefile b/drivers/android/Makefile
> > index c9d3d0c9..c2ffdb6 100644
> > --- a/drivers/android/Makefile
> > +++ b/drivers/android/Makefile
> > @@ -4,3 +4,4 @@ ccflags-y += -I$(src)			# needed for trace events
> >  obj-$(CONFIG_ANDROID_BINDERFS)		+= binderfs.o
> >  obj-$(CONFIG_ANDROID_BINDER_IPC)	+= binder.o binder_alloc.o
> >  obj-$(CONFIG_ANDROID_BINDER_IPC_SELFTEST) += binder_alloc_selftest.o
> > +obj-$(CONFIG_BINDER_TRANSACTION_LATENCY_TRACKING)	+= binder_latency_tracer.o
> > diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> > index 0cab900..65ad38c 100644
> > --- a/drivers/android/binder.c
> > +++ b/drivers/android/binder.c
> > @@ -2674,6 +2674,7 @@ static void binder_transaction(struct binder_proc *proc,
> >  		return_error_line = __LINE__;
> >  		goto err_alloc_t_failed;
> >  	}
> > +	trace_binder_txn_latency_alloc(t);
> >  	INIT_LIST_HEAD(&t->fd_fixups);
> >  	binder_stats_created(BINDER_STAT_TRANSACTION);
> >  	spin_lock_init(&t->lock);
> > @@ -5177,6 +5178,7 @@ static void print_binder_transaction_ilocked(struct seq_file *m,
> >  		   to_proc ? to_proc->pid : 0,
> >  		   t->to_thread ? t->to_thread->pid : 0,
> >  		   t->code, t->flags, t->priority, t->need_reply);
> > +	trace_binder_txn_latency_info(m, t);
> >  	spin_unlock(&t->lock);
> >  
> >  	if (proc != to_proc) {
> > @@ -5818,4 +5820,8 @@ static int __init binder_init(void)
> >  #define CREATE_TRACE_POINTS
> >  #include "binder_trace.h"
> >  
> > +EXPORT_TRACEPOINT_SYMBOL(binder_txn_latency_alloc);
> > +EXPORT_TRACEPOINT_SYMBOL(binder_txn_latency_info);
> > +EXPORT_TRACEPOINT_SYMBOL(binder_txn_latency_free);
> > +
> >  MODULE_LICENSE("GPL v2");
> > diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h
> > index 872232f..309d1b10 100644
> > --- a/drivers/android/binder_internal.h
> > +++ b/drivers/android/binder_internal.h
> > @@ -15,6 +15,11 @@
> >  #include <uapi/linux/android/binderfs.h>
> >  #include "binder_alloc.h"
> >  
> > +#if IS_ENABLED(CONFIG_BINDER_TRANSACTION_LATENCY_TRACKING)
> > +#include <uapi/linux/time_types.h>
> > +#include <linux/rtc.h>
> > +#endif
> > +
> >  struct binder_context {
> >  	struct binder_node *binder_context_mgr_node;
> >  	struct mutex context_mgr_node_lock;
> > @@ -524,6 +529,14 @@ struct binder_transaction {
> >  	 * during thread teardown
> >  	 */
> >  	spinlock_t lock;
> > +	/**
> > +	 * @timestamp and @tv are used to record the time
> > +	 * that the binder transaction startup
> > +	 */
> > +#if IS_ENABLED(CONFIG_BINDER_TRANSACTION_LATENCY_TRACKING)
> > +	struct timespec64 timestamp;
> > +	struct __kernel_old_timeval tv;
> 
> As I stated in the 0/3 email, please use the correct in-kernel structure
> for this.  That structure is _ONLY_ for old userspace api compatibility
> issues.  Which is not the case here at all.
> 
> thanks,
> greg k-h

Since it's not proper to use timeval & __kernel_old_timeval.
The remaining structure with tv_usec that I found is
__kernel_timex_timeval, but I'm not sure if this is proper one or not.
All I can see is in
https://lwn.net/ml/linux-kernel/20180705213604.18883-6-deepa.kernel@gmail.com/

I'm afraid of using wrong structure again.
Could you give me some advices about this?

Or is there another suitable way to replace timeval

Many thanks,
Frankie



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