Re: [PATCH 2/3] lockdep: clarify size for LOCKDEP_*_BITS configs

[Waiman Long]

On 8/5/24 21:01, Carlos Llamas wrote:
> The LOCKDEP_*_BITS configs control the size of internal structures used
> by lockdep. The size is calculated as a power of two of the configured
> value (e.g. 16 => 64KB). Update these descriptions to more accurately
> reflect this, as "Bitsize" can be misleading.
>
> Suggested-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Waiman Long <longman@xxxxxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Signed-off-by: Carlos Llamas <cmllamas@xxxxxxxxxx>
> ---
>   lib/Kconfig.debug | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index baaaedfde0cb..e0614a415348 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -1505,7 +1505,7 @@ config LOCKDEP_SMALL
>   	bool
>   
>   config LOCKDEP_BITS
> -	int "Bitsize for MAX_LOCKDEP_ENTRIES"
> +	int "Size for MAX_LOCKDEP_ENTRIES (as Nth power of 2)"
>   	depends on LOCKDEP && !LOCKDEP_SMALL
>   	range 10 24
>   	default 15
> @@ -1513,7 +1513,7 @@ config LOCKDEP_BITS
>   	  Try increasing this value if you hit "BUG: MAX_LOCKDEP_ENTRIES too low!" message.
>   
>   config LOCKDEP_CHAINS_BITS
> -	int "Bitsize for MAX_LOCKDEP_CHAINS"
> +	int "Size for MAX_LOCKDEP_CHAINS (as Nth power of 2)"
>   	depends on LOCKDEP && !LOCKDEP_SMALL
>   	range 10 21
>   	default 16
> @@ -1521,7 +1521,7 @@ config LOCKDEP_CHAINS_BITS
>   	  Try increasing this value if you hit "BUG: MAX_LOCKDEP_CHAINS too low!" message.
>   
>   config LOCKDEP_STACK_TRACE_BITS
> -	int "Bitsize for MAX_STACK_TRACE_ENTRIES"
> +	int "Size for MAX_STACK_TRACE_ENTRIES (as Nth power of 2)"
>   	depends on LOCKDEP && !LOCKDEP_SMALL
>   	range 10 26
>   	default 19
> @@ -1529,7 +1529,7 @@ config LOCKDEP_STACK_TRACE_BITS
>   	  Try increasing this value if you hit "BUG: MAX_STACK_TRACE_ENTRIES too low!" message.
>   
>   config LOCKDEP_STACK_TRACE_HASH_BITS
> -	int "Bitsize for STACK_TRACE_HASH_SIZE"
> +	int "Size for STACK_TRACE_HASH_SIZE (as Nth power of 2)"
>   	depends on LOCKDEP && !LOCKDEP_SMALL
>   	range 10 26
>   	default 14
> @@ -1537,7 +1537,7 @@ config LOCKDEP_STACK_TRACE_HASH_BITS
>   	  Try increasing this value if you need large STACK_TRACE_HASH_SIZE.
>   
>   config LOCKDEP_CIRCULAR_QUEUE_BITS
> -	int "Bitsize for elements in circular_queue struct"
> +	int "Size for elements in circular_queue struct (as Nth power of 2)"
>   	depends on LOCKDEP
>   	range 10 26
>   	default 12

Many kernel developers understand that BITS refers to a size of 2^n. 
Besides LOCKDEP, there are also many instances of such use in other 
kconfig entries. It can be a bit odd to explicitly state that just for 
LOCKDEP.

Cheers,
Longman