On 10/09/2018 11:39 AM, Lukasz Luba wrote: > This patch add some comment related to performance impact, > which can be really big (x3 times slower context switch). > > Signed-off-by: Lukasz Luba <l.l...@partner.samsung.com> > --- > lib/Kconfig.debug | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 4966c4f..9e67a2a3 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -1088,6 +1088,9 @@ config PROVE_LOCKING > the proof of observed correctness is also maintained for an > arbitrary combination of these separate locking variants. > > + This feature enables LOCKDEP which can harm system performance > + even x3 times. > + > For more details, see Documentation/locking/lockdep-design.txt. > > config LOCK_STAT > @@ -1112,6 +1115,10 @@ config LOCK_STAT > CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. > (CONFIG_LOCKDEP defines "acquire" and "release" events.) > > + This feature enables LOCKDEP which can harm system performance > + even x3 times. > + For more details, see Documentation/locking/lockdep-design.txt. > + > config DEBUG_RT_MUTEXES > bool "RT Mutex debugging, deadlock detection" > depends on DEBUG_KERNEL && RT_MUTEXES > @@ -1175,6 +1182,10 @@ config DEBUG_LOCK_ALLOC > spin_lock_init()/mutex_init()/etc., or whether there is any lock > held during task exit. > > + This feature enables LOCKDEP which can harm system performance > + even x3 times. > + For more details, see Documentation/locking/lockdep-design.txt. > + > config LOCKDEP > bool > depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
I don't mind seeing warning message about the performance impact of enabling lockdep. However, the actual slowdown depends on many factors including the type of systems, workloads and so on. I am a bit hesitant to quote an actual figure like x3 in the help text as it may not be correct in many cases. BTW, my recent lockdep patch (https://lkml.org/lkml/2018/10/2/1410) should be able to reduce the performance impact of enabling lockdep. Could you try to see if that help in your case? Cheers, Longman
