Re: [Yaffs] About nDeletedFiles and nUnlinkedFiles

On Friday 29 November 2013 19:37:13 Oğuzhan Zilci wrote:
> How can I use background garbage collection? Is there a way to start it
> from user space? The only thing I could find about the version of yaffs we
> are using is at the top of yaffs_guts.c file: "yaffs_guts.c 2682 2007-01-22
> 03:19:29Z"
> Is background gc feature available for this version?

You will need a far more recent version to use background gc.

Try integrating the current head of the Yaffs2 git.

-- Charles

> ________________________________________
> From: yaffs [yaffs-bounces@lists.aleph1.co.uk] on behalf of Charles Manning
> [cdhmanning@gmail.com] Sent: Thursday, November 28, 2013 11:24 PM
> To: yaffs@lists.aleph1.co.uk
> Subject: Re: [Yaffs] About nDeletedFiles and nUnlinkedFiles
>
> On Friday 29 November 2013 03:31:25 Oğuzhan Zilci wrote:
> > Dear All,
> >
> > I'm a very new to YAFFS2 and had little experience on flash file systems.
> > We are using YAFFS2 on a 512 MB NAND Chip on an embedded uclinux system.
> > After some read/write/delete etc operations on flash, nDeletedFiles and
> > nUnlinkedFiles (obtained from /proc/yaffs) becomes about 30k-40k and
> > memory footprint of yaffs becomes about 5MB. I test this by running
> > "free" command before and after mounting yaffs2. Are we doing something
> > wrong, is this an expected value? We are running low on system memory and
> > need ever bit of it, can we do some periodic operation (on user space is
> > preferred rather then kernel) to check and clean up nDeletedFiles. I
> > guess since about 5% to 10% of the flash is used in or system, garbage
> > collection mechanism is not started (may be not necessary?), but we need
> > something like that. Creating a huge file on flash (about the size of it)
> > then deleting it increases free memory again. Any comment, suggestion,
> > method, idea is welcomed.
>
> What is happening is that when files in Yaffs2 are deleted, the objects
> still persist in memory until the space where they live is cleared by
> garbage collection.
>
> When you write the large file this forces the garbage collection to happen
> and clean up those files.
>
> It sounds like you are not using background garbage collection. That will
> cause the deleted file data to be freed up.
>
> -- Charles
>
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