[PATCH] smpboot: reuse timer calibration
From: Paul Menzel
Date: Tue Oct 29 2019 - 10:20:03 EST
From: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Date: Wed, 11 Feb 2015 17:28:14 -0600
NO point recalibrating for known-constant tsc ...
saves 200ms+ of boot time.
Signed-off-by: Paul Menzel <pmenzel@xxxxxxxxxxxxx>
---
Arjan, can your Signed-off-by line be added? On what device, did you
test this?
This upstreams the patch from Clear Linux.
https://github.com/clearlinux-pkgs/linux/blob/master/0108-smpboot-reuse-timer-calibration.patch
arch/x86/kernel/tsc.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index c59454c382fd..42b07ed467d2 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1525,6 +1525,9 @@ unsigned long calibrate_delay_is_known(void)
if (!constant_tsc || !mask)
return 0;
+ if (cpu != 0)
+ return cpu_data(0).loops_per_jiffy;
+
sibling = cpumask_any_but(mask, cpu);
if (sibling < nr_cpu_ids)
return cpu_data(sibling).loops_per_jiffy;
--
2.24.0.rc1