Increasing read request size in JFFS2

Increasing read request size in JFFS2

[payagond]

Hi,
I want to know, whether, we can exploit the fast sequential read 
(multiple pages at one go) feature of a nand flash device by existing 
JFFS2 code.
read_pages in readahead decides to call either 
mapping->a_ops->readpages or mapping->a_ops->readpage
can I implement jffs2_readpages to do so?
The problem I feel is (if I have understood correctly)
To read more pages at one shot, we need to anyway read the 
jffs2_raw_inode header first and then calculate the lenth to read, will 
it give me more performance than what is existing?
regards
payagond


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Re: Increasing read request size in JFFS2

[Artem Bityutskiy]

On Fri, 2007-09-14 at 07:24 -0400, payagond@aol.com wrote:
> Hi,
> I want to know, whether, we can exploit the fast sequential read 
> (multiple pages at one go) feature of a nand flash device by existing 
> JFFS2 code.
> read_pages in readahead decides to call either 
> mapping->a_ops->readpages or mapping->a_ops->readpage
> can I implement jffs2_readpages to do so?
> The problem I feel is (if I have understood correctly)
> To read more pages at one shot, we need to anyway read the 
> jffs2_raw_inode header first and then calculate the lenth to read, will 
> it give me more performance than what is existing?
> regards
> payagond

JFFS2 reads maximum 3 2K NAND pages at a time, although very rarely.
Mostly it reads one page if compression is enabled.

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

Re: Increasing read request size in JFFS2

[Josh Boyer]

On Fri, 14 Sep 2007 14:38:27 +0300
Artem Bityutskiy <dedekind@infradead.org> wrote:

> On Fri, 2007-09-14 at 07:24 -0400, payagond@aol.com wrote:
> > Hi,
> > I want to know, whether, we can exploit the fast sequential read 
> > (multiple pages at one go) feature of a nand flash device by existing 
> > JFFS2 code.
> > read_pages in readahead decides to call either 
> > mapping->a_ops->readpages or mapping->a_ops->readpage
> > can I implement jffs2_readpages to do so?
> > The problem I feel is (if I have understood correctly)
> > To read more pages at one shot, we need to anyway read the 
> > jffs2_raw_inode header first and then calculate the lenth to read, will 
> > it give me more performance than what is existing?
> > regards
> > payagond
> 
> JFFS2 reads maximum 3 2K NAND pages at a time, although very rarely.
> Mostly it reads one page if compression is enabled.

And isn't a performance gain only seen if the data is actually
in sequential pages on flash?  For fresh filesystems, that may be true.
But over time, the data for each individual file can scatter everywhere.

josh

need patch for SST39VF301flash chips

[Bruno]

  

Hi...

Has anyone released MTD drivers patch for SST39VF3201 flash chips for linux
kernel 2.4.27?

Need it urgently.

Regards,
Bruno

Re: need patch for SST39VF301flash chips

[Josh Boyer]

On Mon, 2007-09-17 at 15:56 +0530, Bruno wrote:
> 
>   
> 
> Hi...
> 
> Has anyone released MTD drivers patch for SST39VF3201 flash chips for linux
> kernel 2.4.27?
> 
> Need it urgently.

http://linux-mtd.infradead.org/source.html#kernelversions

josh