Messages in this thread | | | Date | Tue, 15 Mar 2022 09:33:08 +0800 | From | Feng Tang <> | Subject | Re: [PATCH v3 1/2] x86/tsc: add a timer to make sure tsc_adjust is always checked |
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Hi Nicolas,
Thanks for raising it.
On Mon, Mar 14, 2022 at 06:52:07PM +0100, Nicolas Saenz Julienne wrote: > Hi Feng, Thomas, > > > On Wed, Nov 17, 2021 at 10:37:51AM +0800, Feng Tang wrote: > > Normally the tsc_sync will get checked every time system enters idle state, > > but Thomas Gleixner mentioned there is still a caveat that a system won't > > enter idle [1], either because it's too busy or configured purposely to not > > enter idle. Setup a periodic timer (every 10 minitues) to make sure the > > check is always on. > > > > [1]. https://lore.kernel.org/lkml/875z286xtk.fsf@nanos.tec.linutronix.de/ > > Signed-off-by: Feng Tang <feng.tang@intel.com> > > I can see this timer interrupting my system's nohz_full CPUs. It'd be nice to > be able to avoid the noise. A solution is using 'tsc=reliable', but IIUC this > is not what the flag was created for. Any ideas/suggestions?
This patch is about correctness. And yes, as you said, the 'tsc=reliable' works. Another thought is to leverage the 'housekeeping_mask' to exclude the isolated nohz_full CPUs, but the 'caveat' what the patch try to solve remains.
Also before this patchset, the clocksource watchdog timer is fired every 500ms, which should interrupt nohz_full CUPS more?
Thanks, Feng
> Regards, > Nicolas
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