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[Xen-devel] Re: [PATCH V3] xen/balloon: Memory hotplug support for Xen b

To: Vasiliy G Tolstov <v.tolstov@xxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH V3] xen/balloon: Memory hotplug support for Xen balloon driver
From: Daniel Kiper <dkiper@xxxxxxxxxxxx>
Date: Wed, 18 May 2011 12:35:43 +0200
Cc: "jeremy@xxxxxxxx" <jeremy@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "haicheng.li@xxxxxxxxxxxxxxx" <haicheng.li@xxxxxxxxxxxxxxx>, "konrad.wilk@xxxxxxxxxx" <konrad.wilk@xxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "dave@xxxxxxxxxxxxxxxxxx" <dave@xxxxxxxxxxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>, "linux-mm@xxxxxxxxx" <linux-mm@xxxxxxxxx>, "wdauchy@xxxxxxxxx" <wdauchy@xxxxxxxxx>, "rientjes@xxxxxxxxxx" <rientjes@xxxxxxxxxx>, "andi.kleen@xxxxxxxxx" <andi.kleen@xxxxxxxxx>, "akpm@xxxxxxxxxxxxxxxxxxxx" <akpm@xxxxxxxxxxxxxxxxxxxx>, "fengguang.wu@xxxxxxxxx" <fengguang.wu@xxxxxxxxx>, Daniel Kiper <dkiper@xxxxxxxxxxxx>
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On Wed, May 18, 2011 at 11:24:54AM +0400, Vasiliy G Tolstov wrote:
> On Wed, 2011-05-18 at 08:21 +0100, Ian Campbell wrote:
> > On Wed, 2011-05-18 at 07:57 +0100, Vasiliy G Tolstov wrote:
> > > On Tue, 2011-05-17 at 23:44 +0200, Daniel Kiper wrote:
> > > > +         Memory could be hotplugged in following steps:
> > > > +
> > > > +           1) dom0: xl mem-max <domU> <maxmem>
> > > > +              where <maxmem> is >= requested memory size,
> > > > +
> > > > +           2) dom0: xl mem-set <domU> <memory>
> > > > +              where <memory> is requested memory size; alternatively 
> > > > memory
> > > > +              could be added by writing proper value to
> > > > +              /sys/devices/system/xen_memory/xen_memory0/target or
> > > > +              /sys/devices/system/xen_memory/xen_memory0/target_kb on 
> > > > dumU,
> > > > +
> > > > +           3) domU: for i in /sys/devices/system/memory/memory*/state; 
> > > > do \
> > > > +                      [ "`cat "$i"`" = offline ] && echo online > 
> > > > "$i"; done
> >
> > > Very good. Is that possible to eliminate step 3 ? And do it automatic if
> > > domU runs with specific xen balloon param?
> >
> > When we faced the same question WRT VCPU hotplug we ended up using a
> > udev rule. Presumably the same could be done here. In the VCPU case the
> > rule is:
> >
> > ACTION=="add", SUBSYSTEM=="cpu", RUN+="/bin/sh -c '[ ! -e 
> > /sys$devpath/online ] || echo 1 > /sys$devpath/online'"
> >
> > Presumably the memory one will be broadly similar.

Here is proper udev rule:

SUBSYSTEM=="memory", ACTION=="add", RUN+="/bin/sh -c '[ -f /sys$devpath/state ] 
&& echo online > /sys$devpath/state'"

Konrad, could you add it to git comment and Kconfig help ???

Daniel

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