RE: [PATCH] xen: Fix selfballooning and ensure it doesn't go too far

[Dan Magenheimer <dan.magenheimer@oracle.com>]

> From: Konrad Rzeszutek Wilk
> Sent: Monday, September 26, 2011 11:23 AM
> To: Dan Magenheimer
> Cc: linux-kernel@vger.kernel.org; xen-devel@lists.xensource.com; David Vrabel; Jeremy Fitzhardinge
> Subject: Re: [PATCH] xen: Fix selfballooning and ensure it doesn't go too far
> 
> On Sat, Sep 24, 2011 at 01:58:08PM -0700, Dan Magenheimer wrote:
> > [PATCH] xen: Fix selfballooning and ensure it doesn't go too far
> >
> > The balloon driver's "current_pages" is very different from
> > totalram_pages.  Self-ballooning needs to be driven by
> > the latter.  Also, Committed_AS doesn't account for pages
> > used by the kernel so enforce a floor for when there
> > are little or no user-space threads using memory.
> 
> Hey Dan,
> ..
> > +		floor_pages = totalreserve_pages +
> > +				(roundup_pow_of_two(max_pfn) >> 5);
> 
> Would it make sense to make the shift be a runtime argument
> in case some users report problems with that calculation?

Good idea.  I'll take a look at that.

> > +		/* don't balloon too far, lest OOMs occur... */
> > +		if (tgt_pages < floor_pages)
> > +			tgt_pages = floor_pages;
> > +		balloon_set_new_target(tgt_pages +
> > +			balloon_stats.current_pages - totalram_pages);
> >  		reset_timer = true;
> >  	}
> >  #ifdef CONFIG_FRONTSWAP
> 
> Otherwise it looks OK to me. Would you like me to queue it up
> for 3.1-rc7?

Will let you know when I have that change done/tested.

Thanks,
Dan