Re: [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
>   patched2647ms2785ms
> 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 
> ---
>  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


-- 
Pengutronix e.K.   | |
Industrial Linux Solutions | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0|
Amtsgericht Hildesheim, HRA 2686   | Fax:   +49-5121-206917- |

___
barebox mailing list
barebox@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/barebox

[RFC] ramfs: rember last accessed chunk

[Jan Weitzel]

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
patched2647ms2785ms
i.MX35 chunk size 8192: 7225ms
patched 2691ms

No impact on much smaller files seen

Signed-off-by: Jan Weitzel 
---
 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;
+   
+   /* 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;
+
+   while (left--)
+   data = data->next;
+
+   node->recent_chunkp = data;
+   node->recent_chunk = chunk;
+
+   return data;
+}
+
 static int ramfs_read(struct device_d *_dev, FILE *f, void *buf, size_t insize)
 {
struct ramfs_inode *node = (struct ramfs_inode *)f->inode;
@@ -311,11 +343,7 @@ static int ramfs_read(struct device_d *_dev, FILE *f, void 
*buf, size_t insize)
debug("%s: reading from chunk %d\n", __FUNCTION__, chunk);
 
/* Position ourself in stream */
-   data = node->data;
-   while (chunk) {
-   data = data->next;
-   chunk--;
-   }
+   data = ramfs_find_chunk(node, chunk);
ofs = f->pos % CHUNK_SIZE;
 
/* Read till end of current chunk */
@@ -364,11 +392,7 @@ static int ramfs_write(struct device_d *_dev, FILE *f, 
const void *buf, size_t i
debug("%s: writing to chunk %d\n", __FUNCTION__, chunk);
 
/* Position ourself in stream */
-   data = node->data;
-   while (chunk) {
-   data = data->next;
-   chunk--;
-   }
+   data = ramfs_find_chunk(node, chunk);
ofs = f->pos % CHUNK_SIZE;
 
/* Write till end of current chunk */
@@ -429,6 +453,8 @@ static int ramfs_truncate(struct device_d *dev, FILE *f, 
ulong size)
ramfs_put_chunk(data);
data = tmp;
}
+   if (node->recent_chunk > newchunks) 
+   node->recent_chunk = 0;
}
 
if (newchunks > oldchunks) {
-- 
1.7.0.4


___
barebox mailing list
barebox@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/barebox