[ Please cc hudson@osresearch.net on any replies. Thank you! ]
A few months ago I noticed gettimeofday running backwards on
dual Pentium II and dual Pentium Pro systems with 2.4.18. Based
on postings made to linux-kernel in June of 2002, I upgraded
to 2.4.20 and the problem seemed to go away:
3D16DE83.3060409@tiscalinet.it">http://groups.google.com/groups?threadm=3D16DE83.3060409@tiscalinet.it
Just recently my NAS benchmarks and MPI latency tests showed bizarre
results, so I pulled out my test program and am seeing the same
problems again. It seems that roughly 50 in 1 million calls go
backwards, even with 2.4.20.
Occasionally it is 4295 seconds (very consistently that value),
but most of them are just a few microseconds backwards. No error
code is returned from the system call either. No NTP or rdate type
services are running.
My test program can be seen here:
http://www.swcp.com/~hudson/gettimeofday.c
Interestingly, it only happens on the compute nodes with NFS root.
The service node has booted from a local SCSI disk and is serving roughly
140 compute nodes without any timing bugs.
service:~/tflop-linux: ssh node-181 uname -a \; cat /proc/cpuinfo
Linux node-181 2.4.20 #73 SMP Mon Apr 21 14:06:49 MDT 2003 i686 unknown
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 3
model name : Pentium II (Klamath)
stepping : 2
cpu MHz : 333.356
cache size : 512 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
bogomips : 665.19
processor : 1
vendor_id : GenuineIntel
cpu family : 6
model : 3
model name : Pentium II (Klamath)
stepping : 2
cpu MHz : 333.356
cache size : 512 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
bogomips : 665.19
Trammell
-- -----|----- hudson@osresearch.net W 240-283-1700 *>=====[]L\ hudson@rotomotion.com M 505-463-1896 ' -'-`- http://www.swcp.com/~hudson/ KC5RNF- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Wed Apr 23 2003 - 22:00:35 EST