Re: [PATCH] kdump: fix OOM issue when vm.min_free_kbytes is set too high

[Vivek Goyal]

On Fri, Dec 05, 2014 at 09:57:41PM +0530, Hari Bathini wrote:
> On 12/05/2014 08:41 PM, Vivek Goyal wrote:
> > On Tue, Nov 25, 2014 at 11:42:20AM +0530, Hari Bathini wrote:
> > > When the value of vm.min_free_kbytes is set too high in /etc/sysctl.conf,
> > > kdump kernel fails with OOM. As min_free_kbytes may not be relevant for
> > > kdump kernel, this patch tries to fix the issue by removing it from the
> > > file sysctl.conf and thus forcing default value for vm.min_free_kbytes
> > > parameter.
> > > Signed-off-by: Hari Bathini
> > >
> > > dracut-module-setup.sh |    5 +++++
> > >  1 file changed, 5 insertions(+)
> > >
> > > diff --git a/dracut-module-setup.sh b/dracut-module-setup.sh
> > > index dcebc47..6ada7d3 100755
> > > --- a/dracut-module-setup.sh
> > > +++ b/dracut-module-setup.sh
> > > @@ -612,6 +612,11 @@ install() {
> > >      # Also redirect dracut-emergency to kdump error handler
> > >      ln_r "$systemdsystemunitdir/emergency.service" "$systemdsystemunitdir/dracut-emergency.service"
> > > # While min_free_kbytes may not be relevant for kdump kernel,
> > > # it leads to OOM in cases where this value is too high.
> > > # Let's be paranoid and force it to default value calculated in kernel.
> > > sed -e "/^$/d" -e "/^#/d" -e "/min_free_kbytes/d" /etc/sysctl.conf > "${initdir}/etc/sysctl.conf"
> >
> > Hari,
> >
> > which service inside dracut applies forces these parameters? It does
> > sound like a problem in kdump environment because lot of these settings
> > might make sense in first kernel (when all cpus and memory is available)
> > but might not make sense in second kernel.
> >
> > It would be preferrable if we can override those settings based on user
> > inputs instead of hardcoding these. Having said that I am not finding
> > any way to do that.
> >
> > So I guess for the time being we can take this patch. If more problems
> > like this crop up, we might have to request dracut guys to provide us
> > a command line option where sysctl options can be specified and user
> > will need to provide those command line options.
> >
> > So I guess for the time being we can take this patch. If more problems
> > like this crop up, we might have to request dracut guys to provide us
> > a command line option where sysctl options can be specified and user
> > will need to provide those command line options.
> >
> > w.r.t patch, what are expressions "-e "/^$/d"" and -e "/^#/d"?
>
> Since we are here, thought of cleaning the sysctl.conf file in kdump initrd
> by deleting empty lines and comment lines respectively, as done for
> kdump.conf file

Ok, I don't think it was required but I am not particular about it. So..

Acked-by: Vivek Goyal

Thanks
Vivek