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>
diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c
index 068759d..be72903 100644
--- a/arch/x86/kernel/tsc_32.c
+++ b/arch/x86/kernel/tsc_32.c
@@ -401,6 +401,7 @@
void __init tsc_init(void)
{
int cpu;
+ u64 lpj;
if (!cpu_has_tsc || tsc_disabled) {
/* Disable the TSC in case of !cpu_has_tsc */
@@ -421,6 +422,10 @@
return;
}
+ lpj = ((u64)tsc_khz * 1000);
+ do_div(lpj, HZ);
+ lpj_tsc = lpj;
+
printk("Detected %lu.%03lu MHz processor.\n",
(unsigned long)cpu_khz / 1000,
(unsigned long)cpu_khz % 1000);