Messages in this thread | | | From | Ani Sinha <> | Date | Wed, 7 Jul 2021 17:15:53 +0530 (IST) | Subject | Re: [PATCH v2] sched/clock: print a log when the sched clock is marked unstable |
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On Wed, 7 Jul 2021, Peter Zijlstra wrote:
> On Wed, Jul 07, 2021 at 04:26:59PM +0530, Ani Sinha wrote: > > When the sched clock transitions from stable to unstable and > > vice versa, a kernel log is printed. When the sched clock > > is marked explicitly as unstable, make __clear_sched_clock_stable() > > emit a warning log. It is useful for example in understanding > > why a certain feature like NOHZ that depends on availability of a > > stable sched clock, is not available. > > > > Signed-off-by: Ani Sinha <ani@anisinha.ca> > > --- > > kernel/sched/clock.c | 1 + > > 1 file changed, 1 insertion(+) > > > > Changelog: > > V1: original patch > > v2: print pr_warn from __clear_sched_clock_stable instead. Commit log > > updated with proper prefix and wording. > > > > diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c > > index c2b2859ddd82..99484fec0335 100644 > > --- a/kernel/sched/clock.c > > +++ b/kernel/sched/clock.c > > @@ -183,6 +183,7 @@ static void __clear_sched_clock_stable(void) > > return; > > > > tick_dep_set(TICK_DEP_BIT_CLOCK_UNSTABLE); > > + pr_warn("sched_clock: Marking unstable.\n"); > > schedule_work(&sched_clock_work); > > } > > I'm confused... that work has a ton of printk()s in, what is this > pr_warn() adding? >
Right, but for whatever reason, on latest version of Ubuntu (21.04) running on hyperV, I do not see those logs:
azureuser@CentOS:~$ uname -a Linux CentOS 5.11.0-1009-azure #9-Ubuntu SMP Thu Jun 17 02:20:07 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux azureuser@CentOS:~$ dmesg | grep unstable dmesg: read kernel buffer failed: Operation not permitted azureuser@CentOS:~$ sudo su root@CentOS:/home/azureuser# dmesg | grep unstable [ 0.000000] tsc: Marking TSC unstable due to running on Hyper-V root@CentOS:/home/azureuser# dmesg | grep sched [ 0.384656] rcu: RCU calculated value of scheduler-enlistment delay is 25 jiffies. [ 1.122977] io scheduler mq-deadline registered root@CentOS:/home/azureuser# exit
Hence, I was trying the patch.
A
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