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@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'.
}
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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?