Messages in this thread | | | From | Pranith Kumar <> | Date | Sat, 26 Jul 2014 21:51:52 -0400 | Subject | Re: [PATCH RFC tip/core/rcu] Fix attempt to avoid offloading callbacks unless requested |
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On Fri, Jul 25, 2014 at 10:30 PM, Frederic Weisbecker <fweisbec@gmail.com> wrote:
>> I understand that if CONFIG_NO_HZ_FULL_ALL is set then CONFIG_NOCB_CPU_ALL >> will also be set and there is no need for this cpumask_or(). >> >> Is there any reason for the coupling between CONFIG_NO_HZ_FULL_ALL >> and CONFIG_NOCB_CPU_ALL? > > Yeah, for any nohz full CPU, we need the corresponding CPU to be rcu_nocb. > So if all CPUs are full dynticks, all CPUs must be rcunocb. > > That said with this patch, the dependency is perhaps not needed anymore. > >> >> I ask because a user can override CONFIG_NO_HZ_FULL_ALL=y at boot time >> using the nohz_full= boot time parameter. > > No, the content of nohz_full= is ignored with CONFIG_NO_HZ_FULL_ALL=y. >
Please correct me if I am wrong but that does not seem to be the case. If a boot parameter is passed, we are setting up tick_nohz_full_mask from tick_nohz_full_setup() and marking tick_nohz_full_running as true. Later on we check this flag and skip the CONFIG_NO_HZ_FULL_ALL initialization.
> That said you made me check and I realize that when that happens, we alloc > the mask two times and we leak the first. I need to fix that.
This does not actually happen as we do the initialization only once. Am I missing something?
> > Thanks.
-- Pranith
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