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xen-devel
Re: [Xen-devel] XEN 4.0 + 2.6.31.13 pvops kernel : system crashes on sta
I did a little testing.
With no kernel option:
# dmesg | grep -i nr_irqs
[ 0.000000] nr_irqs_gsi: 88
[ 0.000000] NR_IRQS:4352 nr_irqs:256
w/nr_irqs=65536:
# dmesg | grep -i nr_irqs
[ 0.000000] Command line: root=/dev/sda1 ro quiet console=hvc0
nr_irqs=65536
[ 0.000000] nr_irqs_gsi: 88
[ 0.000000] Kernel command line: root=/dev/sda1 ro quiet console=hvc0
nr_irqs=65536
[ 0.000000] NR_IRQS:4352 nr_irqs:256
tweaking the NR_IRQS macro in the kernel will change the NR_IRQS output,
but unfortunately that doesn't change nr_irqs and I run into the same
limit (36 domus on a less-beefy dual core machine).
I did find this:
http://blogs.sun.com/fvdl/entry/a_million_vms
which references NR_DYNIRQS, which is in 2.6.18, but not in the pvops
kernel.
Watching /proc/interrupts, the domain irqs seem to be getting allocated
from 248 downward until they hit some other limit:
...
64: 59104 xen-pirq-ioapic-level ioc0
89: 1 xen-dyn-event evtchn:xenconsoled
90: 1 xen-dyn-event evtchn:xenstored
91: 6 xen-dyn-event vif36.0
92: 140 xen-dyn-event blkif-backend
93: 97 xen-dyn-event evtchn:xenconsoled
94: 139 xen-dyn-event evtchn:xenstored
95: 7 xen-dyn-event vif35.0
96: 301 xen-dyn-event blkif-backend
97: 261 xen-dyn-event evtchn:xenconsoled
98: 145 xen-dyn-event evtchn:xenstored
99: 7 xen-dyn-event vif34.0
...
Perhaps the xen irqs are getting allocated out of the nr_irqs pool,
while they could be allocated from the NR_IRQS pool?
-John
On 04/27/2010 08:45 PM, Keir Fraser wrote:
I think nr_irqs is specifiable on the command line on newer kernels. You may
be able to do nr_irqs=65536 as a kernel boot parameter, or something like
that, without needing to rebuild the kernel.
-- Keir
On 28/04/2010 02:02, "Yuvraj Agarwal"<yuvraj@xxxxxxxxxxx> wrote:
Actually, I did identify the problem (don’t know the fix) at least from
the console logs. Its related to running out of nr_irq's (attached JPG
for the console log).
-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Keir Fraser
Sent: Tuesday, April 27, 2010 5:44 PM
To: Yuvraj Agarwal; xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] XEN 4.0 + 2.6.31.13 pvops kernel : system crashes
on starting 155th domU
On 27/04/2010 08:41, "Yuvraj Agarwal"<yuvraj@xxxxxxxxxxx> wrote:
Attached is the output of /var/log/daemon.log and /var/log/xen/xend.log,
but
as far as we can see we don¹t quite know what might be going causing the
system to crash (no console access anymore and system becomes
unresponsive and
needs to be power-cycled). I have pasted only the relevant bits of
information (the last domU that did successfully start and the next one
that
failed). It may be the case that all the log messages weren¹t flushed
before
the system crashedŠ
Does anyone know where this limit of 155 domU is coming from and how we
can
fix/increase it?
Get a serial line on a test box, and capture Xen logging output on it. You
can both see if any crash messages come from Xen when the 155th domain is
created, and also try the serial debug keys (e.g., try 'h' to get help to
start with) to see whether Xen itself is still alive.
-- Keir
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