[PING][PATCH 2/2] Document the M_ARENA_* mallopt parameters

[Siddhesh Poyarekar <siddhesh at gotplt dot org>]

Ping!

On Monday 10 October 2016 10:56 PM, Siddhesh Poyarekar wrote:
> The M_ARENA_* mallopt parameters are in wide use in production to
> control the number of arenas that a long lived process creates and
> hence there is no point in stating that this interface is non-public.
> Document this interface and remove the obsolete comment.
> 
> 	* manual/memory.texi (M_ARENA_TEST): Add documentation.
> 	(M_ARENA_MAX): Likewise.
> 	* malloc/malloc.c: Remove obsolete comment.
> ---
>  malloc/malloc.c    |  1 -
>  manual/memory.texi | 21 +++++++++++++++++++++
>  2 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/malloc/malloc.c b/malloc/malloc.c
> index 09e004b..0011a6d 100644
> --- a/malloc/malloc.c
> +++ b/malloc/malloc.c
> @@ -1718,7 +1718,6 @@ static struct malloc_par mp_ =
>  };
>  
>  
> -/*  Non public mallopt parameters.  */
>  #define M_ARENA_TEST -7
>  #define M_ARENA_MAX  -8
>  
> diff --git a/manual/memory.texi b/manual/memory.texi
> index 222f126..b98dcf2 100644
> --- a/manual/memory.texi
> +++ b/manual/memory.texi
> @@ -1153,6 +1153,27 @@ order to return memory to the system.
>  
>  This parameter can also be set for the process at startup by setting the
>  environment variable @code{MALLOC_TRIM_THRESHOLD_} to the desired value.
> +
> +@item M_ARENA_TEST
> +An arena is a memory pool that is allocated to act as a heap alongside the
> +system heap that the kernel creates for the process.  This is to provide
> +multiple heap structures for multiple threads of a process to reduce contention
> +between them.  The limit to the number of such arenas per process is determined
> +by the number of cores of the system and whether it is a 32-bit or a 64-bit
> +processor.
> +
> +The value is ignored if @code{M_ARENA_MAX} is set either via @code{mallopt} or
> +via the @code{MALLOC_ARENA_MAX} environment variable.
> +
> +This parameter can also be set for the process at startup by setting the
> +environment variable @code{MALLOC_ARENA_TEST} to the desired value.
> +
> +@item M_ARENA_MAX
> +This parameter sets the number of arenas to use regardless of the number of
> +cores in the system.
> +
> +This parameter can also be set for the process at startup by setting the
> +environment variable @code{MALLOC_ARENA_MAX} to the desired value.
>  @end table
>  
>  @end deftypefun
>