On 11/22/17 at 11:25am, Baoquan He wrote:
On 11/22/17 at 11:17am, Dave Young wrote:
> Hi Baoquan,
>
> On 11/21/17 at 05:07pm, Baoquan He wrote:
> > In commit:
> >
> > commit 2040103bd7 ("kdumpctl: sanity check of nr_cpus for x86_64 in case
running out of vectors")
> >
> > ... function check_kdump_cpus() was introduced to check if number of cpu
> > is enough to boot to provide enough interrupt vectors.
> >
> > As we know, there are 256 interrupt vectors on each cpu to correspond to
> > irq. Except of those system reserved vectors, only part of 256 will be
> > used for device. So if there are many IO devices on a system, E.g more
> > than 256 irqs are needed to map, then specifying 'nr_cpus=1' in kernel
> > cmdline may not work. Especially on large NUMA system, with multiple
> > cpus and multiple devices.
> >
> > However, usually firmware engineer will consider the irq number
> > corresponding to IO devices and CPU number, so it's not a problem for
> > normal kernel. In kdump kernel, it may be a problem since we default to
> > specify 'nr_cpus=1' in kernel cmdline. Or maybe not, because for many
> > devices which is not needed for vmcore dumping, drivers related to them
> > are not added to kdump kernel, then the message 'Warning: nr_cpus=1 may
> > not be enough for kdump boot' could be false positive to a large extent.
> > So in this patch, change 'Warning: ...' to 'Note: ...' so that
QA or
> > customers won't open bug for a false positive report.
> >
> > Signed-off-by: Baoquan He <bhe(a)redhat.com>
> > ---
> > kdumpctl | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kdumpctl b/kdumpctl
> > index d4e00503a221..012369da8879 100755
> > --- a/kdumpctl
> > +++ b/kdumpctl
> > @@ -171,7 +171,7 @@ check_kdump_cpus()
> > return
> > fi
> >
> > - echo -n "Warning: nr_cpus=1 may not be enough for kdump boot,"
> > + echo -n "[Note]: nr_cpus=1 may not be enough for kdump boot,"
>
> It looks better to remove the brackets.
OK, will change. thx
>
> > echo " try nr_cpus=$nr_min or larger instead"
>
> this sentence can also be changed to for example:
> try nr_cpus=$nr_min or larger instead if nr_cpus=1 does not work.
This is one sentence with the above 'Note' one since the above printing
uses 'echo -n'.
>
> > }
> >
> > --
> > 2.5.5
> > _______________________________________________
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>
> Thanks
> Dave
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BTW, Baoquan, as we know this message appears in a test on a 4T machine,
have you get chance to test nr_cpus=1 on 1st kernel, does it work?