From: Arjan van de Ven <[email protected]>
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 <[email protected]>
---
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
On Tue, Oct 29, 2019 at 03:19:57PM +0100, Paul Menzel wrote:
> From: Arjan van de Ven <[email protected]>
> 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 <[email protected]>
> ---
>
> Arjan, can your Signed-off-by line be added? On what device, did you test
> this?
This patch makes no sense what so ever given the current function, also
it hard codes 0 as being the BSP.
All of this for platforms (!constant_tsc) that barely exist anymore.
On Tue, 29 Oct 2019, Peter Zijlstra wrote:
> On Tue, Oct 29, 2019 at 03:19:57PM +0100, Paul Menzel wrote:
> > From: Arjan van de Ven <[email protected]>
> > 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 <[email protected]>
> > ---
> >
> > Arjan, can your Signed-off-by line be added? On what device, did you test
> > this?
>
> This patch makes no sense what so ever given the current function, also
> it hard codes 0 as being the BSP.
>
> All of this for platforms (!constant_tsc) that barely exist anymore.
And it's only an issue on multi-socket systems with !constant_tsc, which
are even more rare.
Thanks,
tglx