linux-kernel - Re: [Xen-devel] Re: [PATCH R3 5/7] xen/balloon: Protect against CPU exhaust by event/x proces

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Date:	Thu, 10 Feb 2011 12:10:20 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Daniel Kiper <dkiper@...-space.pl>
Cc:	jeremy@...p.org, xen-devel@...ts.xensource.com,
	ian.campbell@...rix.com, haicheng.li@...ux.intel.com,
	linux-kernel@...r.kernel.org, dan.magenheimer@...cle.com,
	v.tolstov@...fip.ru, dave@...ux.vnet.ibm.com, linux-mm@...ck.org,
	rientjes@...gle.com, andi.kleen@...el.com,
	akpm@...ux-foundation.org, fengguang.wu@...el.com,
	wdauchy@...il.com
Subject: Re: [Xen-devel] Re: [PATCH R3 5/7] xen/balloon: Protect against
 CPU exhaust by event/x proces

On Thu, Feb 10, 2011 at 10:51:42AM -0500, Konrad Rzeszutek Wilk wrote:
> On Thu, Feb 03, 2011 at 05:28:51PM +0100, Daniel Kiper wrote:
> > Protect against CPU exhaust by event/x process during
> > errors by adding some delays in scheduling next event.
> > 
> > Signed-off-by: Daniel Kiper <dkiper@...-space.pl>
> > ---
> >  drivers/xen/balloon.c |   99 +++++++++++++++++++++++++++++++++++++++---------
> >  1 files changed, 80 insertions(+), 19 deletions(-)
> > 
> > diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> > index 4223f64..ed103d4 100644
> > --- a/drivers/xen/balloon.c
> > +++ b/drivers/xen/balloon.c
> > @@ -66,6 +66,20 @@
> >  
> >  #define BALLOON_CLASS_NAME "xen_memory"
> >  
> > +/*
> > + * balloon_process() state:
> > + *
> > + * BP_ERROR: error, go to sleep,
> > + * BP_DONE: done or nothing to do,
> > + * BP_HUNGRY: hungry.
> > + */
> > +
> > +enum bp_state {
> > +	BP_ERROR,
> 
> BP_EAGAIN?
> 
> So if we fail to increase the first hour, we would keep on trying to
> increase forever (with a 32 second delay between each call). Do you
> think it makes sense (as a future patch, not tied in with this patchset)
> to printout a printk(KERN_INFO that we have been trying to increase
> for the last X hours, seconds and have not gone anywhere (and perhaps
> stop trying to allocate more memory?).

Duh, you did that in the next patch with the mh_policy.
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