Hi Longman, Thanks for the patches. I have applied them and run on ARM. In context switch test, there is ~2% improvement (but still ~15us instead of 5-6us). In dhrystone: test results are the same. There is also 2% improvement in boot time.
You can add me on CC list if you have some patches related to this feature. I will give it a try on arm platforms. Regards, Lukasz On 10/09/2018 07:29 PM, Waiman Long wrote: > 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 > > > >
