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

[Alexey Kardashevskiy]

On 09/05/16 21:13, 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.
>
> Before this patch:
>
> real	0m2.214s
> user	0m0.015s
> sys	  0m0.006s
>
> real	0m2.222s
> user	0m0.014s
> sys	  0m0.005s
>
> real	0m2.201s
> user	0m0.010s
> sys	  0m0.005s
>
> After this patch:
>
> real	0m1.762s
> user	0m0.014s
> sys	  0m0.006s
>
> real	0m1.773s
> user	0m0.011s
> sys   0m0.004s
>
> real	0m1.754s
> user	0m0.013s
> sys	  0m0.005s

Thanks, applied.

btw have you received a mail from the patchworks that the patch status has 
changed? If so, I would prefer not to generate more noise with these 
"applied" messages in the maillist if possible.


>
> 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);
>  }
>


-- 
Alexey