Hello Ed

NOR is very slow to erase and this is what is causing the issues.


On Tue, May 6, 2014 at 6:15 AM, Ed Sutter <ed.sutter@alcatel-lucent.com>wrote:

> Hi,
> I have YAFFS running in standalone mode for about a year now.
> My underlying memory is NOR, and generally speaking I see a
> write rate of about 1Mbyte every 3 seconds.  I have not tuned
> the underlying flash accesses so I'm sure there's room for
> improvement there.
>
> The problem I am having is that as I add files (and remove them)
> I notice more and more that the 3 seconds turns into 10-15
> seconds occasionally.  I assume yaffs is doing some garbage
> collection; however it seems to occure a lot more often than
> necessary.  Is garbage collection likely the culprit?  If yes,
> is there any tuning that can be done to adjust how often that
> is done?
>

There is some tuning, but perhaps a better option is to get a background
thread going for doing the gc. This will clean the decks  for writes to
occur unimpeded.

How full is the file system?


> Also, is it correct to observe that the removal of a file takes
> essentially the same amount of time as adding a file?
>

Are you using Yaffs1 mode of operation? When a file is deleted the chunks
are marked deleted and when all the chunks in a file are deleted, the
erasure will occur. This can take some time.


Are you using the "soft delete" feature? This defers the actual deletion,
but unless you have background gc running, this will just move the delays
into the gc.

Let's see what we can work out here.

Regards

Charles