Re: dom0 linux 3.6.0-rc4, crash due to ballooning althoug dom0_mem=X, max:X set

From: Sander Eikelenboom <linux@eikelenboom.it>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Robert Phillips <robert.phillips@citrix.com>,
	Ben Guthro <ben@guthro.net>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: dom0 linux 3.6.0-rc4, crash due to ballooning althoug dom0_mem=X, max:X set
Date: Thu, 6 Sep 2012 13:16:55 +0200	[thread overview]
Message-ID: <899997008.20120906131655@eikelenboom.it> (raw)
In-Reply-To: <20120906105746.GA3668@phenom.dumpdata.com>

Thursday, September 6, 2012, 12:57:46 PM, you wrote:

>> > About nine of them deal with dom0_mem=max ballooning up right, so if you
>> > ignore those:
>> 
>> > b9e0d95 xen: mark local pages as FOREIGN in the m2p_override
>> > d79d595 xen: Add selfballoning memory reservation tunable.
>> > f62805f xen: enter/exit lazy_mmu_mode around m2p_override calls
>> 
>> > Try reverting any of those.
>> 
>> Ah i missed your email since my hostingprovider was down :-(
>> But anyway done a git bisect in the mean time that leads to:
>> 
>> [f62805f1f30a40e354bd036b4cb799863a39be4b] xen: enter/exit lazy_mmu_mode around m2p_override calls

> OK. Hmm.that will take a bit of thinking to fix.
>> 
>> 
>> > And if nothing works there then we can try to revert the ones that
>> > deal with 'dom0_mem=max:XX'..
>> 
>> > I also need to be able to reproduce this. You said you can only reproduce this
>> > on your Intel box - is this a fast Intel machine? It also looks like you only
>> > have 2GB in the machine - and reserve 1GB to the dom0.
>> 
>> Machine is a quad core q9400 @ 2.66mhz, not very fast .. not very slow either

> That is a fast machine. I was thinking you had a Core2 Solo or a Pentium IV Prescott.

>> 
>> > If you manually (so don't start the guest), balloon down - say to 512MB and then launch
>> > a guest do you see this problem?
>> 
>> 
>> Should i use
>> 
>> xl  mem-max domain-id mem
>> 
>> or
>> 
>> xl  mem-set domain-id mem

Will test that shortly

> The later.
>> 
>> for that ?
>> 
>> 
>> Perhaps a silly question, but why is it ballooning anyway ?
>> I have set dom0's memory and there is enough left to create the domain ... or at least there should be ...

> There was a bug in xl that would autoballoon. You can turn it off using some xl.conf file.

Should that have been fixed ?
       A) you describe it as a bug, so even without tinkering with the default xl.conf, the tools shouldn't be autoballooning when "dom0_mem=X, max:X" is set right ?)
       B) or was it fixed by letting the user turn it off in xl.conf ?

If A .. That would make that the "bug" is still present in xen-4.2-rc4 ...

Because i was under the impression the "dom0_mem=X, max:X" would prevent the whole autoballooning stuff :-)

>> 
>> --
>> Sander