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author | Alok Kataria <akataria@vmware.com> | 2008-06-20 15:06:33 -0700 |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2008-06-23 22:51:33 +0200 |
commit | 3da757daf86e498872855f0b5e101f763ba79499 (patch) | |
tree | bffffafed7322c66a1b886b661cfd8a8a7f5a924 /init | |
parent | e01b70ef3eb3080fecc35e15f68cd274c0a48163 (diff) | |
download | kernel_samsung_aries-3da757daf86e498872855f0b5e101f763ba79499.zip kernel_samsung_aries-3da757daf86e498872855f0b5e101f763ba79499.tar.gz kernel_samsung_aries-3da757daf86e498872855f0b5e101f763ba79499.tar.bz2 |
x86: use cpu_khz for loops_per_jiffy calculation
On the x86 platform we can use the value of tsc_khz computed during tsc
calibration to calculate the loops_per_jiffy value. Its very important
to keep the error in lpj values to minimum as any error in that may
result in kernel panic in check_timer. In virtualization environment, On
a highly overloaded host the guest delay calibration may sometimes
result in errors beyond the ~50% that timer_irq_works can handle,
resulting in the guest panicking.
Does some formating changes to lpj_setup code to now have a single
printk to print the bogomips value.
We do this only for the boot processor because the AP's can have
different base frequencies or the BIOS might boot a AP at a different
frequency.
Signed-off-by: Alok N Kataria <akataria@vmware.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Daniel Hecht <dhecht@vmware.com>
Cc: Tim Mann <mann@vmware.com>
Cc: Zach Amsden <zach@vmware.com>
Cc: Sahil Rihan <srihan@vmware.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'init')
-rw-r--r-- | init/calibrate.c | 36 |
1 files changed, 19 insertions, 17 deletions
diff --git a/init/calibrate.c b/init/calibrate.c index ecb3822..8628697 100644 --- a/init/calibrate.c +++ b/init/calibrate.c @@ -8,7 +8,9 @@ #include <linux/delay.h> #include <linux/init.h> #include <linux/timex.h> +#include <linux/smp.h> +unsigned long lpj_tsc; unsigned long preset_lpj; static int __init lpj_setup(char *str) { @@ -108,6 +110,10 @@ static unsigned long __cpuinit calibrate_delay_direct(void) {return 0;} * This is the number of bits of precision for the loops_per_jiffy. Each * bit takes on average 1.5/HZ seconds. This (like the original) is a little * better than 1% + * For the boot cpu we can skip the delay calibration and assign it a value + * calculated based on the tsc frequency. + * For the rest of the CPUs we cannot assume that the tsc frequency is same as + * the cpu frequency, hence do the calibration for those. */ #define LPS_PREC 8 @@ -118,20 +124,20 @@ void __cpuinit calibrate_delay(void) if (preset_lpj) { loops_per_jiffy = preset_lpj; - printk("Calibrating delay loop (skipped)... " - "%lu.%02lu BogoMIPS preset\n", - loops_per_jiffy/(500000/HZ), - (loops_per_jiffy/(5000/HZ)) % 100); + printk(KERN_INFO + "Calibrating delay loop (skipped) preset value.. "); + } else if ((smp_processor_id() == 0) && lpj_tsc) { + loops_per_jiffy = lpj_tsc; + printk(KERN_INFO + "Calibrating delay loop (skipped), " + "using tsc calculated value.. "); } else if ((loops_per_jiffy = calibrate_delay_direct()) != 0) { - printk("Calibrating delay using timer specific routine.. "); - printk("%lu.%02lu BogoMIPS (lpj=%lu)\n", - loops_per_jiffy/(500000/HZ), - (loops_per_jiffy/(5000/HZ)) % 100, - loops_per_jiffy); + printk(KERN_INFO + "Calibrating delay using timer specific routine.. "); } else { loops_per_jiffy = (1<<12); - printk(KERN_DEBUG "Calibrating delay loop... "); + printk(KERN_INFO "Calibrating delay loop... "); while ((loops_per_jiffy <<= 1) != 0) { /* wait for "start of" clock tick */ ticks = jiffies; @@ -161,12 +167,8 @@ void __cpuinit calibrate_delay(void) if (jiffies != ticks) /* longer than 1 tick */ loops_per_jiffy &= ~loopbit; } - - /* Round the value and print it */ - printk("%lu.%02lu BogoMIPS (lpj=%lu)\n", - loops_per_jiffy/(500000/HZ), - (loops_per_jiffy/(5000/HZ)) % 100, - loops_per_jiffy); } - + printk(KERN_INFO "%lu.%02lu BogoMIPS (lpj=%lu)\n", + loops_per_jiffy/(500000/HZ), + (loops_per_jiffy/(5000/HZ)) % 100, loops_per_jiffy); } |