Re: Fwd: Control page reclaim granularity

[Zheng Liu]

On Tue, Mar 13, 2012 at 01:17:41PM +0530, Kautuk Consul wrote:
> On Tue, Mar 13, 2012 at 1:13 PM, Kautuk Consul <consul.kautuk@xxxxxxxxx> wrote:
> > Hi,
> >
> > I noticed this discussion and decided to pitch in one small idea from my side.
> >
> > It would be nice to range lock an inode's pages by storing those
> > ranges which would be locked.
> > This could also add some good routines for the kernel in terms of
> > range locking for a single inode.
> > However, wouldn't this add some overhead to shrink_page_list() since
> > that code would need to go through
> > all these ranges while trying to reclaim a single page ?
> >
> > One small suggestion from my side is:
> > Why don't we implement something like : "Complete page-cache reclaim
> > control from usermode"?
> > In this, we can set/unset the mapping to AS_UNEVICTABLE (as Konstantin
> > mentioned) for a file's
> > inode from usermode by using ioctl or fcntl or maybe even go as far as
> > implementing an O_NORECL
> > option to the open system call.
> >
> 
> Of course, only an application executing with root privileges should
> be allowed to set the inode's
> mapping flags in this manner.

Hi Kautuk,

IMHO, running application with root privilege is too dangerous.  We
should avoid it.

Regards,
Zheng

> 
> 
> > After setting the AS_UNEVICTABLE, the usermode application can choose
> > to keep and remove pages by
> > using the fadvise(WILLNEED) and fadvise(DONTNEED).
> >
> > ( I think maybe the presence of any VMA is might not really be
> > required for this idea. )
> >
> > Thanks,
> > Kautuk.
> 
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