[RFC] ramfs: rember last accessed chunk

[Sascha Hauer]

Hi Jan,

On Tue, May 15, 2012 at 11:15:46AM +0200, Jan Weitzel wrote:
> Writing big files takes longer and longer because of the chunk list
> By storing a pointer of the recent used chunk in the inode, access times are
> improved.
> Testet on with tftp 10M:
> OMAP4 chunk size 4096: 12244ms 8192: 4239ms
> 	patched        2647ms        2785ms
> i.MX35 chunk size 8192: 7225ms
> 	patched		2691ms
> 

The numbers look good and the code looks sane. We can give it a try. Two
nitpicks below.

> No impact on much smaller files seen
> 
> Signed-off-by: Jan Weitzel <j.weitzel at phytec.de>
> ---
>  fs/ramfs.c |   46 ++++++++++++++++++++++++++++++++++++----------
>  1 files changed, 36 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/ramfs.c b/fs/ramfs.c
> index 83ab6df..5c7410b 100644
> --- a/fs/ramfs.c
> +++ b/fs/ramfs.c
> @@ -48,6 +48,10 @@ struct ramfs_inode {
>  
>  	ulong size;
>  	struct ramfs_chunk *data;
> +	

Trailing whitespace here.

> +	/* Points to recently used chunk */
> +	int recent_chunk;
> +	struct ramfs_chunk *recent_chunkp;
>  };
>  
>  struct ramfs_priv {
> @@ -297,6 +301,34 @@ static int ramfs_close(struct device_d *dev, FILE *f)
>  	return 0;
>  }
>  
> +static struct ramfs_chunk *ramfs_find_chunk(struct ramfs_inode *node, int chunk)
> +{
> +	struct ramfs_chunk *data;
> +	int left = chunk;
> +
> +	if (chunk == 0)
> +		return node->data;
> +
> +	if (node->recent_chunk == chunk)
> +		return node->recent_chunkp;
> +
> +	if (node->recent_chunk < chunk && node->recent_chunk != 0) {
> +		/* Start at last known chunk */
> +		data = node->recent_chunkp;
> +		left -= node->recent_chunk;
> +	} else
> +		/* Start at first chunk */
> +		data = node->data;

if you have brackets in the if path you should add them in the else path
aswell.

>  		}
> +		if (node->recent_chunk > newchunks) 

Also trailing whitespace

Sascha


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