Re: [GIT PULL] isolation: 1Hz residual tick offloading v4

[Luiz Capitulino]

On Mon, 29 Jan 2018 16:54:31 +0100
Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> On Mon, Jan 29, 2018 at 10:33:16AM -0500, Luiz Capitulino wrote:
> > Cool, passing tsc=reliable worked for me. I finally got to the tick to
> > go completely away. While I agree that fixing that is beyond the scope
> > of this series, I think we should improve it anyway since it will probably
> > come up for people trying the new nohz_full=.  
> 
> The only way to fix that is to audit all BIOS code :/ Short of that, we
> need to periodically test the TSC on each CPU/SOCKET to verify its still
> in step with expectation.

Oh, OK. I thought we could find a way to avoid the timer in the kernel
for certain CPUs like mine.

Thanks for the explanation.

> 
> Sadly MSR_IA32_TSC and MSR_IA32_TSC_ADJUST are writable registers and
> BIOS monkeys occasionally write to them for 'raisins-of-insanity'.
>