Re: [PATCH 00/19] pramfs

[Marco Stornelli]

Il 08/09/2013 11:05, Vladimir Davydov ha scritto:
> On 09/07/2013 08:22 PM, Marco Stornelli wrote:
> > Il 07/09/2013 16:58, richard -rw- weinberger ha scritto:
> > > On Sat, Sep 7, 2013 at 10:14 AM, Marco Stornelli
> > > <marco.stornelli@xxxxxxxxx> wrote:
> > > > Hi all,
> > > >
> > > > this is an attempt to include pramfs in mainline. At the moment pramfs
> > > > has been included in LTSI kernel. Since last review the code is more
> > > > or less the same but, with a really big thanks to Vladimir Davydov and
> > > > Parallels, the development of fsck has been started and we have now
> > > > the possibility to correct fs errors due to corruption. It's a "young"
> > > > tool but we are working on it. You can clone the code from our repos:
> > > >
> > > > git clone git://git.code.sf.net/p/pramfs/code pramfs-code
> > > > git clone git://git.code.sf.net/p/pramfs/Tools pramfs-Tools
> > >
> > > I'm a bit confused, what kind of non-volatile RAM is your fs targeting?
> > > Wouldn't it make sense to use pstore like
> > > arch/powerpc/platforms/pseries/nvram.c does?
> >
> > Usually battery-backed SRAM, but actually it can be used in any piece
> > of ram directly accessible and it provides a normal and complete fs
> > interface. Usually I do the fs test remapping my system ram. You can
> > find documentation here:
> >
> > http://pramfs.sourceforge.net
>
> I'd like to add that in contrast to pstore, pramfs allows storing any
> files in it, not only system logs. This can be of value even on machines
> w/o special devices like sram/nvram: one can store data that should be
> quickly restored after reboot in conventional ram and use kexec to boot
> to a new kernel. One of the use cases of this could be checkpointing
> time-critical services to ram (using criu.org) to be quickly restored
> after a kernel update providing almost zero-downtime.

Yep. I add that if you use your system ram, your bootloader must be 
aware because it mustn't clear your memory after a reboot, indeed you 
can find reference of Pramfs in Uboot documentation:

http://www.denx.de/wiki/view/DULG/PersistentRAMFileSystem

Marco
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