I've noticed that about half the time, the kernels I build take what I
think is a long time (> 20 seconds) in calibrate_delay().
That is, there is quite a pause between
Calibrating delay loop...
and (the answer, of sorts)
133.12 BogoMIPS
=> bootm ff800000
## Booting image at ff800000 ...
Image Name: Musenki kernel 2.4.19pre1
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 674330 Bytes = 658 kB = 0 MB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
Uncompressing Kernel Image ... OK
Memory BAT mapping: BAT2=32Mb, BAT3=0Mb, residual: 0Mb
Linux version 2.4.19pre1 (jim at ford) (gcc version 2.95.4 20011002 (Debian
prerelease)) #4 Fri Apr 19 05:58:00 CDT 2002
Musenki M3/M1: See www.musenki.com for details
On node 0 totalpages: 8192
zone(0): 8192 pages.
zone(1): 0 pages.
zone(2): 0 pages.
Kernel command line: root=/dev/nfs rw
nfsroot=192.168.0.8:/usr/local/m1_nfsroot
ip=192.168.0.42:192.168.0.8:192.168.0.1:255.255.255.0:fuckme::off
OpenPIC Version 1.2 (1 CPUs and 138 IRQ sources) at fc040000
time_init: decrementer frequency = 25.000000 MHz
Calibrating delay loop... 133.12 BogoMIPS
Memory: 30452k available (1200k kernel code, 480k data, 88k init, 0k
highmem)
Dentry-cache hash table entries: 4096 (order: 3, 32768 bytes)
Inode-cache hash table entries: 2048 (order: 2, 16384 bytes)
Mount-cache hash table entries: 512 (order: 0, 4096 bytes)
Buffer-cache hash table entries: 1024 (order: 0, 4096 bytes)
Page-cache hash table entries: 8192 (order: 3, 32768 bytes)
POSIX conformance testing by UNIFIX
PCI: Probing PCI hardware
[...]
I, as on so many other machines in arch/ppc/platforms/, set
loops_per_jiffy = 50000000 / HZ;
as the first line of musenki_setup_arch(), though I've tried
"100000000 / HZ;" with no difference in effect.
Interestingly, loops_per_jiffy is apparently over-written when
calibrate_delay() is called:
void __init calibrate_delay(void)
{
unsigned long ticks, loopbit;
int lps_precision = LPS_PREC;
loops_per_jiffy = (1<<12);
printk("Calibrating delay loop... ");
while (loops_per_jiffy <<= 1) {
/* wait for "start of" clock tick */
ticks = jiffies;
while (ticks == jiffies)
/* nothing */;
/* Go .. */
ticks = jiffies;
__delay(loops_per_jiffy);
ticks = jiffies - ticks;
if (ticks)
break;
}
/* Do a binary approximation to get loops_per_jiffy set to equal one clock
(up to lps_precision bits) */
loops_per_jiffy >>= 1;
loopbit = loops_per_jiffy;
while ( lps_precision-- && (loopbit >>= 1) ) {
loops_per_jiffy |= loopbit;
ticks = jiffies;
while (ticks == jiffies);
ticks = jiffies;
__delay(loops_per_jiffy);
if (jiffies != ticks) /* longer than 1 tick */
loops_per_jiffy &= ~loopbit;
}
/* Round the value and print it */
printk("%lu.%02lu BogoMIPS\n",
loops_per_jiffy/(500000/HZ),
(loops_per_jiffy/(5000/HZ)) % 100);
}
anyone have a clue to offer?
Jim
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