Re: [Xen-devel] Timer ISR Errors?

["Jeremy Miracle" <jeremy@xxxxxxxx>]

They're pretty intermittent, so its hard to give an exact guess. The host
system is a dual xeon 2.4 with HTT.. here's some info:

Host:
vlink:~# xm info
system                 : Linux
host                   : vlink
release                : 2.6.9-xen0
version                : #4 Fri Dec 3 22:00:29 EST 2004
machine                : i686
cores                  : 2
hyperthreads_per_core  : 2
cpu_mhz                : 2399
memory                 : 1023
free_memory            : 622

vlink:~# xm list
Name              Id  Mem(MB)  CPU  State  Time(s)  Console
Domain-0           0      123    0  r----     65.2
vlink              3      255    1  -b---     27.1    9603

vlink:~# cat /proc/interrupts
           CPU0
 14:      20730        Phys-irq  ide0
 18:     435145        Phys-irq  eth1
 19:     467659        Phys-irq  eth0
128:          1     Dynamic-irq  misdirect
129:         41     Dynamic-irq  ctrl-if
130:  136374838     Dynamic-irq  timer
131:         40     Dynamic-irq  console
132:          0     Dynamic-irq  net-be-dbg
133:      11859     Dynamic-irq  blkif-backend
134:       1439     Dynamic-irq  vif3.0
NMI:          0
ERR:          0


Guest Info:
iad1-uml:/var/log# cat /proc/interrupts
           CPU0
128:          1     Dynamic-irq  misdirect
129:      19804     Dynamic-irq  ctrl-if
130:  118967169     Dynamic-irq  timer
131:      10672     Dynamic-irq  blkif
132:       1705     Dynamic-irq  eth0
NMI:          0
ERR:          0

Thanks,
Jeremy

Keir Fraser said:
>
> How often do you get these messages? It is only showing you to be out
> by about 130us, but I don't really see how even that can happen. Also,
> the rate at which the below stream is coming out is about one error
> per 15us, which is very rapid indeed. Is this running on CPU0 or CPU1
> (on an SMP system)?
>
> You might want to try changing the start of do_timer_interrupt() in
> arch/xen/i386/kernel/time.c to what I have attached just below.
>
> Another thing is to build Xen with performance counters (perfc=y make)
> and then use the xenperf utility to see how many times Xen's scheduler
> is being entered (this might account for the high rate of timer
> interrupts you are seeing). Also looking at cat /proc/interrupts in
> DOM1 may be interesting...
>
>  -- Keir
>
> static inline void do_timer_interrupt(int irq, void *dev_id,
>                                         struct pt_regs *regs)
> {
>         time_t wtm_sec, sec;
>         s64 delta, nsec;
>         long sec_diff, wtm_nsec;
>         /* XXX New declarations below. */
>         static s64 pdelta, pshadow, pprocessed, poffset;
>
>         do {
>                 __get_time_values_from_xen();
>
>                 delta = (s64)(shadow_system_time +
>                               ((s64)cur_timer->get_offset() *
>                                (s64)NSEC_PER_USEC) -
>                               processed_system_time);
>         }
>         while (!TIME_VALUES_UP_TO_DATE);
>
>         if (unlikely(delta < 0)) {
>                 printk("Timer ISR: Time went backwards: %lld %lld %lld
> %lld\n",
>                        delta, shadow_system_time,
>                        ((s64)cur_timer->get_offset() *
> (s64)NSEC_PER_USEC),
>                        processed_system_time);
>                 /* XXX New printk below. &/
>                 printk(" ** %lld %lld %lld %lld\n",
>                        pdelta, pshadow, pprocessed, poffset);
>                 return;
>         }
>
>         /* XXX New assignments below. */
>         pdelta = delta;
>         pshadow = shadow_system_time;
>         pprocessed = processed_system_time;
>         poffset = (s64)cur_timer->get_offset();
>
>
>> Hello All,
>>
>> I'm getting the following error from one of my guest domains (domain
>> 1)..
>>
>> Dec 12 16:41:00 iad1-uml kernel: Timer ISR: Time went backwards: -124000
>> 1367865
>> 0000000 9876000 13678660000000
>> Dec 12 16:41:00 iad1-uml kernel: Timer ISR: Time went backwards: -109000
>> 1367865
>> 0000000 9891000 13678660000000
>> Dec 12 16:41:00 iad1-uml kernel: Timer ISR: Time went backwards: -94000
>> 13678650
>> 000000 9906000 13678660000000
>> Dec 12 16:41:00 iad1-uml kernel: Timer ISR: Time went backwards: -82000
>> 13678650
>> 000000 9918000 13678660000000
>> Dec 12 16:41:00 iad1-uml kernel: Timer ISR: Time went backwards: -66000
>> 13678650
>> 000000 9934000 13678660000000
>> Dec 12 16:41:00 iad1-uml kernel: Timer ISR: Time went backwards: -52000
>> 13678650
>> 000000 9948000 13678660000000
>> Dec 12 16:41:00 iad1-uml kernel: Timer ISR: Time went backwards: -37000
>> 13678650
>> 000000 9963000 13678660000000
>> Dec 12 16:41:00 iad1-uml kernel: Timer ISR: Time went backwards: -24000
>> 13678650
>> 000000 9976000 13678660000000
>> Dec 12 16:41:00 iad1-uml kernel: Timer ISR: Time went backwards: -6000
>> 136786500
>> 00000 9994000 13678660000000
>>
>> Anyone else seen this or know what to do about it?
>>
>> The main system isn't experiencing any related errors of this sort....
>>
>> Thanks,
>> Jeremy
>>
>>
>>
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>



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