On Wed, Dec 31, 2003 at 07:05:53PM +0530, Srivatsa Vaddagiri wrote:
> More debugging reveals that the page fault happens
> always while doing a prefetch. The prefetch is
> present inside list_for_each_entry macros.
>
> For now I have disabled the x86 prefetch function
> to do nothing.
>
> The test seems to run fine so far w/o any of the
> page faults I was experiencing. Will update
> at the end of the overnight run if I hit the problem again.
>
> Wonder if prefetch has some issues on Intel x86 (P3) SMP systems?
>
Even after disabling prefetch, I continue
to hit page-faults.
With prefetch disabled, it _always_
traps because of trying to dereference a NULL pointer in a
list-head. If I break-in into the debugger, the
list-head is actually valid (no NULL pointer is present) and
hence I don't understand why it read a NULL pointer value in
a list head.
With prefetch enabled it traps
because of fetch from arbitrary (random) addresses.
So I am no longer sure if this is a prefetch issue
or/and a hotplug issue. I'm continuing to investigate
and will post any new observation I make here.
FYI, the /proc/cpuinfo output on my SMP system is as below:
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 10
model name : Pentium III (Cascades)
stepping : 1
cpu MHz : 699.730
cache size : 1024 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr sse
bogomips : 1376.25
processor : 1
vendor_id : GenuineIntel
cpu family : 6
model : 10
model name : Pentium III (Cascades)
stepping : 1
cpu MHz : 699.726
cache size : 1024 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr sse
bogomips : 1396.73
processor : 2
vendor_id : GenuineIntel
cpu family : 6
model : 10
model name : Pentium III (Cascades)
stepping : 1
cpu MHz : 699.726
cache size : 1024 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr sse
bogomips : 1396.73
processor : 3
vendor_id : GenuineIntel
cpu family : 6
model : 10
model name : Pentium III (Cascades)
stepping : 1
cpu MHz : 699.726
cache size : 1024 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr sse
bogomips : 1396.73
--
Thanks and Regards,
Srivatsa Vaddagiri,
Linux Technology Center,
IBM Software Labs,
Bangalore, INDIA - 560017