Messages in this thread | | | From | Ani Sinha <> | Date | Sat, 3 Jul 2021 22:59:35 +0530 | Subject | Re: [PATCH v1] Add info log when user enables NOHZ in commandline but NOHZ is not possible |
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ping ...
On Sun, Jun 27, 2021 at 12:58 PM Ani Sinha <ani@anisinha.ca> wrote: > > Commit 4f49b90abb4aca ("sched-clock: Migrate to use new tick > dependency mask model") had also removed the kernel warning > message informing the user that it was not possible to turn > on NO_HZ_FULL. This warning was added in commit e12d0271774fe > ("nohz: Warn if the machine can not perform nohz_full") in order > to warn users when they enabled NOHZ using the kernel commandline > but kernel could not enable NOHZ. Removal of this log defeats this > purpose because we still do not want users thinking that they are > getting the benefit of nohz when their machine can not support it. > Hence this patch brings back the information log. > > If at some point the conditions that prevented NOHZ from being > enabled goes away and the previous info log was printed, we print > another log informing the user that NOHZ was again possible. > > Signed-off-by: Ani Sinha <ani@anisinha.ca> > --- > kernel/time/tick-sched.c | 21 ++++++++++++++++++--- > 1 file changed, 18 insertions(+), 3 deletions(-) > > See also thread: https://lkml.org/lkml/2021/6/20/32 > > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > index 828b091501ca..fbef95b57b1d 100644 > --- a/kernel/time/tick-sched.c > +++ b/kernel/time/tick-sched.c > @@ -930,6 +930,7 @@ static void tick_nohz_full_update_tick(struct tick_sched *ts) > { > #ifdef CONFIG_NO_HZ_FULL > int cpu = smp_processor_id(); > + static bool no_tick_warned; > > if (!tick_nohz_full_cpu(cpu)) > return; > @@ -937,10 +938,24 @@ static void tick_nohz_full_update_tick(struct tick_sched *ts) > if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE) > return; > > - if (can_stop_full_tick(cpu, ts)) > + if (can_stop_full_tick(cpu, ts)) { > tick_nohz_stop_sched_tick(ts, cpu); > - else if (ts->tick_stopped) > - tick_nohz_restart_sched_tick(ts, ktime_get()); > + if (no_tick_warned) { > + pr_info("NO_HZ_FULL is now enabled in the system.\n"); > + no_tick_warned = false; > + } > + } else { > + /* > + * Don't allow the user to think they can get > + * full NO_HZ with this machine. > + */ > + if (!no_tick_warned && tick_nohz_full_running) { > + pr_info("NO_HZ_FULL has been disabled in the system."); > + no_tick_warned = true; > + } > + if (ts->tick_stopped) > + tick_nohz_restart_sched_tick(ts, ktime_get()); > + } > #endif > } > > -- > 2.25.1 >
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