--=_courier-9433-1048049439-0001-2
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
Hi,
On a dual SMP box running SuSE-2.4.19-79 (United Linux rc4), the boot
time in /proc/stat can vary 1 second when read. I haven't seen this
on a UP box. Its not a major issue, but I guess its a hindrance if
one's expecting it to never change:
gen2 12:06:52 ~: grep btime /proc/stat
btime 1046838984
gen2 12:07:06 ~: grep btime /proc/stat
btime 1046838984
gen2 12:07:07 ~: grep btime /proc/stat
btime 1046838983
gen2 12:07:07 ~: grep btime /proc/stat
btime 1046838983
gen2 12:07:08 ~: grep btime /proc/stat
btime 1046838983
gen2 12:07:09 ~: grep btime /proc/stat
btime 1046838984
gen2 12:07:10 ~: grep btime /proc/stat
btime 1046838984
gen2 12:07:11 ~: grep btime /proc/stat
btime 1046838983
I'm not familiar with the way IO-APIC timers work or the interrupt
timer itself, so can someone explain why this is the case? I'm
guessing that it might simply be a timing issue between when the
actual interrupt handling updating jiffies in do_timer and the bottom
half updating xtime.tv_sec (see kernel/timer.c).
Maybe by caching the btime value so that its only calculated once is
the way to go. Attached is the suggested fix, as well as the output
from /proc/cpuinfo & /proc/interrupts.
If someone could get back to me on this it would be much appreciated.
Thanks,
-- Kingsley--=_courier-9433-1048049439-0001-2 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=gen2cpuinfo
processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 6 model name : Celeron (Mendocino) stepping : 5 cpu MHz : 548.544 cache size : 128 KB physical id : 0 threads : 1 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 : 1094.45
processor : 1 vendor_id : GenuineIntel cpu family : 6 model : 6 model name : Celeron (Mendocino) stepping : 5 cpu MHz : 548.544 cache size : 128 KB physical id : 0 threads : 1 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 : 1094.45
--=_courier-9433-1048049439-0001-2 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=gen2interrupts
CPU0 CPU1 0: 61761933 59169714 IO-APIC-edge timer 1: 163 212 IO-APIC-edge keyboard 2: 0 0 XT-PIC cascade 4: 184 160 IO-APIC-edge serial 8: 1 0 IO-APIC-edge rtc 12: 0 0 IO-APIC-edge PS/2 Mouse 14: 3191782 3055354 IO-APIC-edge ide0 15: 0 2 IO-APIC-edge ide1 16: 12195142 12320072 IO-APIC-level eth0 NMI: 0 0 LOC: 120928241 120928231 ERR: 0 MIS: 0
--=_courier-9433-1048049439-0001-2 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="btime.diff"
--- fs/proc/proc_misc.c.old Wed Mar 19 15:21:20 2003 +++ fs/proc/proc_misc.c Wed Mar 19 15:31:36 2003 @@ -250,6 +250,7 @@ static int kstat_read_proc(char *page, char **start, off_t off, int count, int *eof, void *data) { + static unsigned long btime = 0UL; int i, len; extern unsigned long total_forks; unsigned long jif = jiffies; @@ -314,12 +315,15 @@ } } + if (!btime) + btime = xtime.tv_sec - jif / HZ; + len += sprintf(page + len, "\nctxt %lu\n" "btime %lu\n" "processes %lu\n", nr_context_switches(), - xtime.tv_sec - jif / HZ, + btime, total_forks); return proc_calc_metrics(page, start, off, count, eof, len);
--=_courier-9433-1048049439-0001-2--