RFS on the Flash device

Chris Johns chrisj at rtems.org
Sun Sep 25 22:34:16 UTC 2011

On 23/09/11 9:09 PM, ali nasir wrote:
> Hi,
> Is there a minimum size limit for the flash device? for eg is it possible to have the RFS implemented in a single sector of 64K size?

I am not sure what the minimum size would be. I suspect 64K would be too 
small. The overhead of the meta data could be more than the remaining 
data space. The RFS is not designed for media this small.

> What is the use of compact_segs and avail_compact_segs in the struct rtems_flashdisk_config? Are they related to the device?

The comments in the header file state:

  * The compacting segment count is the number of segments that are
  * moved into a new segment. A high number will mean more segments with
  * low active page counts and high used page counts will be moved into
  * available pages how-ever this extends the compaction time due to
  * time it takes the erase the pages. There is no point making this
  * number greater than the maximum number of pages in a segment.
  * The available compacting segment count is the level when compaction
  * occurs when writing. If you set this to 0 then compaction will fail
  * because there will be no segments to compact into.

It controls the frequency or rate of compaction. Too frequent compaction 
slows the file system.


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