[SLOF] [PATCH v2] rtas-nvram: optimize erase

[Thomas Huth]

On 09.05.2016 13:13, Nikunj A Dadhania wrote:
> As this was done at byte granularity, erasing complete nvram(64K
> default) took a lot of time. To reduce the number of rtas call per byte
> write which is expensive, the erase is done at one shot using the
> nvram_buffer that is initiated during the nvram_init call for
> RTAS_NVRAM.
> 
> After this patch there is ~450msec improvement during boot. Default qemu
> booting does not provide file backed nvram, so every boot there would be
> full erase of 64K.
...
> Signed-off-by: Nikunj A Dadhania <nikunj at linux.vnet.ibm.com>
> ---
>  lib/libnvram/nvram.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/lib/libnvram/nvram.c b/lib/libnvram/nvram.c
> index 473814e..99deb2a 100644
> --- a/lib/libnvram/nvram.c
> +++ b/lib/libnvram/nvram.c
> @@ -373,6 +373,17 @@ void erase_nvram(int offset, int len)
>  {
>  	int i;
>  
> +#ifdef RTAS_NVRAM
> +	char *erase_buf = get_nvram_buffer(len);
> +	if (erase_buf) {
> +		/* Speed up by erasing all memory at once */
> +		memset(erase_buf, 0, len);
> +		nvram_store(offset, erase_buf, len);
> +		free_nvram_buffer(erase_buf);
> +		return;
> +	}
> +	/* If get_nvram_buffer failed, fall through to default code */
> +#endif
>  	for (i=offset; i<offset+len; i++)
>  		nvram_write_byte(i, 0);
>  }
> 

Reviewed-by: Thomas Huth <thuth at redhat.com>