From mboxrd@z Thu Jan 1 00:00:00 1970 From: Olaf Hering Subject: Re: [PATCH] xl.cfg: document the maxmem= option Date: Mon, 7 May 2012 15:06:06 +0200 Message-ID: <20120507130605.GA781@aepfle.de> References: <20120504194222.GA28634@phenom.dumpdata.com> <20120504201802.GA16466@aepfle.de> <1336296932.5933.9.camel@cthulhu.hellion.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1336296932.5933.9.camel@cthulhu.hellion.org.uk> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: "xen-devel@lists.xensource.com" , Konrad Rzeszutek Wilk List-Id: xen-devel@lists.xenproject.org On Sun, May 06, Ian Campbell wrote: > On Fri, 2012-05-04 at 16:18 -0400, Olaf Hering wrote: > > On Fri, May 04, Konrad Rzeszutek Wilk wrote: > > > > > On Fri, May 04, 2012 at 09:31:42PM +0200, Olaf Hering wrote: > > > > # HG changeset patch > > > > # User Olaf Hering > > > > # Date 1336159720 -7200 > > > > # Node ID c414728d0d12f1c3e416e40cceefca2f0b00578e > > > > # Parent 8f556a70ae0bef47e242f9e7be0a054769fc8277 > > > > xl.cfg: document the maxmem= option > > > > > > > > Signed-off-by: Olaf Hering > > > > > > > > diff -r 8f556a70ae0b -r c414728d0d12 docs/man/xl.cfg.pod.5 > > > > --- a/docs/man/xl.cfg.pod.5 > > > > +++ b/docs/man/xl.cfg.pod.5 > > > > @@ -484,6 +484,14 @@ are not using hardware assisted paging ( > > > > mode) and your guest workload consists of a a very large number of > > > > similar processes then increasing this value may improve performance. > > > > > > > > +=item B > > > > + > > > > +Specifies the maximum amount of memory the HVM guest can ever see. > > > > > > Isn't it also for PV guests (though without the PoD functionality)? > > > > Now that I look again at libxl__build_pre(), it appearently does also > > something for PV guests. > > Right. Some people call this booting "pre-ballooned". Essentially n PV > the balloon driver can be initialised early enough that something like > PoD is not required -- the missing pages are just incorporated directly > into the balloon. What about this wording? Specifies the maximum amount of memory a guest can ever see. The value of maxmem= must be equal or greater than memory=. In combination with the memory= option it will start the guest "pre-ballooned". In a HVM guest it will enable the PoD (populate on demand) mode, iff the values of memory= and maxmem= differ. The guest needs a balloon driver in this case, without a balloon driver it will crash. Olaf