[U-Boot] [PATCH v3 4/6] dlmalloc: add option for skip memset in malloc init

[Masahiro Yamada]

Hi Przemyslaw,


On Fri, 20 Feb 2015 12:06:17 +0100
Przemyslaw Marczak <p.marczak at samsung.com> wrote:

> This commit introduces new config: CONFIG_SYS_MALLOC_INIT_SKIP_ZEROING.
> 
> Before this change, the all amount of memory reserved for the malloc,
> was set to zero in mem_malloc_init(). When the malloc reserved memory
> exceeds few MiB, then the boot process can slow down.
> 
> So enabling this config, is an option to reduce the boot time.
> 
> This option can be enabled by Kconfig.
> 
> Note:
> After enable this option, only calloc() will return the pointer to zeroed
> memory area. Previously, without this option, the memory pointed to untouched
> malloc memory region, was filled with zeros. So it means, that code with
> malloc() calls should be reexamined.
> 
> Signed-off-by: Przemyslaw Marczak <p.marczak at samsung.com>
> Reviewed-by: Simon Glass <sjg at chromium.org>
> 
> ---
> Changes v3:
> - squash the commit with the Kconfig option
> ---
>  Kconfig           | 26 +++++++++++++++++++-------
>  common/dlmalloc.c | 10 +++++++---
>  2 files changed, 26 insertions(+), 10 deletions(-)
> 
> diff --git a/Kconfig b/Kconfig
> index 75bab7f..87d4daf 100644
> --- a/Kconfig
> +++ b/Kconfig
> @@ -76,13 +76,25 @@ config SYS_MALLOC_F_LEN
>  	  initial serial device and any others that are needed.
>  
>  menuconfig EXPERT
> -        bool "Configure standard U-Boot features (expert users)"
> -        help
> -          This option allows certain base U-Boot options and settings
> -          to be disabled or tweaked. This is for specialized
> -          environments which can tolerate a "non-standard" U-Boot.
> -          Only use this if you really know what you are doing.
> -
> +	bool "Configure standard U-Boot features (expert users)"
> +	help
> +	  This option allows certain base U-Boot options and settings
> +	  to be disabled or tweaked. This is for specialized
> +	  environments which can tolerate a "non-standard" U-Boot.
> +	  Only use this if you really know what you are doing.
> +
> +if EXPERT
> +	config SYS_MALLOC_INIT_SKIP_ZEROING
> +	bool "Skip memset at malloc init (reduce boot time)"
> +	help
> +	  This avoids zeroing memory reserved for malloc at malloc init.
> +	  Significant boot time reduction is visible for configs in which
> +	  CONFIG_SYS_MALLOC_LEN value, has more than few MiB.
> +	  Useful for bzip2, bmp logo.
> +	  Warning:
> +	  When enabling this, please check if malloc calls, maybe
> +	  should be replaced by calloc - if expects zeroed memory.
> +endif
>  endmenu		# General setup
>  
>  menu "Boot images"
> diff --git a/common/dlmalloc.c b/common/dlmalloc.c
> index 6453ee9..63f68ed 100644
> --- a/common/dlmalloc.c
> +++ b/common/dlmalloc.c
> @@ -1535,9 +1535,9 @@ void mem_malloc_init(ulong start, ulong size)
>  
>  	debug("using memory %#lx-%#lx for malloc()\n", mem_malloc_start,
>  	      mem_malloc_end);
> -
> -	memset((void *)mem_malloc_start, 0, size);
> -
> +#ifndef CONFIG_SYS_MALLOC_INIT_SKIP_ZEROING
> +	memset((void *)mem_malloc_start, 0x0, size);
> +#endif
>  	malloc_bin_reloc();
>  }
>  
> @@ -2948,10 +2948,12 @@ Void_t* cALLOc(n, elem_size) size_t n; size_t elem_size;
>  
>  
>    /* check if expand_top called, in which case don't need to clear */
> +#ifndef CONFIG_SYS_MALLOC_INIT_SKIP_ZEROING
>  #if MORECORE_CLEARS
>    mchunkptr oldtop = top;
>    INTERNAL_SIZE_T oldtopsize = chunksize(top);
>  #endif
> +#endif
>    Void_t* mem = mALLOc (sz);
>  
>    if ((long)n < 0) return NULL;
> @@ -2977,6 +2979,7 @@ Void_t* cALLOc(n, elem_size) size_t n; size_t elem_size;
>  
>      csz = chunksize(p);
>  
> +#ifndef CONFIG_SYS_MALLOC_INIT_SKIP_ZEROING
>  #if MORECORE_CLEARS
>      if (p == oldtop && csz > oldtopsize)
>      {
> @@ -2984,6 +2987,7 @@ Void_t* cALLOc(n, elem_size) size_t n; size_t elem_size;
>        csz = oldtopsize;
>      }
>  #endif
> +#endif
>  
>      MALLOC_ZERO(mem, csz - SIZE_SZ);
>      return mem;


You are adding only "ifndef" conditionals.

IMHO,
Isn't "#ifdef CONFIG_SYS_MALLOC_INIT_ZEROING" better?
(Generally speaking, CONFIG options that disable a feature are not preferable.)

You also need to add "default y" to the Kconfig
and add "# CONIFG_SYS_MALLOC_INIT_ZEROING is not set" to your defconfig.


Best Regards
Masahiro Yamada