package/base/linux/0108-smpboot-reuse-timer-calibration.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Arjan van de Ven <arjan@linux.intel.com>
   3 Date: Wed, 11 Feb 2015 17:28:14 -0600
   4 Subject: [PATCH] smpboot: reuse timer calibration
   5
   6 NO point recalibrating for known-constant tsc ...
   7 saves 200ms+ of boot time.
   8 ---
   9  arch/x86/kernel/tsc.c | 3 +++
  10  1 file changed, 3 insertions(+)
  11
  12 diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
  13 index 49d925043171..704733712ec4 100644
  14 --- a/arch/x86/kernel/tsc.c
  15 +++ b/arch/x86/kernel/tsc.c
  16 @@ -1546,6 +1546,9 @@ unsigned long calibrate_delay_is_known(void)
  17         if (!constant_tsc || !mask)
  18                 return 0;
  19
  20 +       if (cpu != 0)
  21 +               return cpu_data(0).loops_per_jiffy;
  22 +
  23         sibling = cpumask_any_but(mask, cpu);
  24         if (sibling < nr_cpu_ids)
  25                 return cpu_data(sibling).loops_per_jiffy;
  26 --
  27 https://clearlinux.org
  28