* [PATCH] rcu: Only boost rcu reader tasks with lower priority than boost kthreads @ 2022-03-04 9:26 Zqiang 2022-03-04 11:42 ` Neeraj Upadhyay 0 siblings, 1 reply; 8+ messages in thread From: Zqiang @ 2022-03-04 9:26 UTC (permalink / raw) To: paulmck, frederic, quic_neeraju; +Cc: linux-kernel When RCU_BOOST is enabled, the boost kthreads will boosting readers who are blocking a given grace period, if the current reader tasks have a higher priority than boost kthreads(the boost kthreads priority not always 1, if the kthread_prio is set), boosting is useless, skip current task and select next task to boosting, reduce the time for a given grace period. Signed-off-by: Zqiang <qiang1.zhang@intel.com> --- kernel/rcu/tree_plugin.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index c3d212bc5338..d35b6da66bbd 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -12,6 +12,7 @@ */ #include "../locking/rtmutex_common.h" +#include <linux/sched/deadline.h> static bool rcu_rdp_is_offloaded(struct rcu_data *rdp) { @@ -1065,13 +1066,20 @@ static int rcu_boost(struct rcu_node *rnp) * section. */ t = container_of(tb, struct task_struct, rcu_node_entry); + if (!rnp->exp_tasks && (dl_task(t) || t->prio <= current->prio)) { + tb = rcu_next_node_entry(t, rnp); + WRITE_ONCE(rnp->boost_tasks, tb); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + goto end; + } + rt_mutex_init_proxy_locked(&rnp->boost_mtx.rtmutex, t); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); /* Lock only for side effect: boosts task t's priority. */ rt_mutex_lock(&rnp->boost_mtx); rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */ rnp->n_boosts++; - +end: return READ_ONCE(rnp->exp_tasks) != NULL || READ_ONCE(rnp->boost_tasks) != NULL; } -- 2.25.1 ^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH] rcu: Only boost rcu reader tasks with lower priority than boost kthreads 2022-03-04 9:26 [PATCH] rcu: Only boost rcu reader tasks with lower priority than boost kthreads Zqiang @ 2022-03-04 11:42 ` Neeraj Upadhyay 2022-03-07 2:03 ` Zhang, Qiang1 0 siblings, 1 reply; 8+ messages in thread From: Neeraj Upadhyay @ 2022-03-04 11:42 UTC (permalink / raw) To: Zqiang, paulmck, frederic; +Cc: linux-kernel On 3/4/2022 2:56 PM, Zqiang wrote: > When RCU_BOOST is enabled, the boost kthreads will boosting readers > who are blocking a given grace period, if the current reader tasks > have a higher priority than boost kthreads(the boost kthreads priority > not always 1, if the kthread_prio is set), boosting is useless, skip > current task and select next task to boosting, reduce the time for a > given grace period. > > Signed-off-by: Zqiang <qiang1.zhang@intel.com> > --- > kernel/rcu/tree_plugin.h | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > index c3d212bc5338..d35b6da66bbd 100644 > --- a/kernel/rcu/tree_plugin.h > +++ b/kernel/rcu/tree_plugin.h > @@ -12,6 +12,7 @@ > */ > > #include "../locking/rtmutex_common.h" > +#include <linux/sched/deadline.h> > > static bool rcu_rdp_is_offloaded(struct rcu_data *rdp) > { > @@ -1065,13 +1066,20 @@ static int rcu_boost(struct rcu_node *rnp) > * section. > */ > t = container_of(tb, struct task_struct, rcu_node_entry); > + if (!rnp->exp_tasks && (dl_task(t) || t->prio <= current->prio)) { > + tb = rcu_next_node_entry(t, rnp); > + WRITE_ONCE(rnp->boost_tasks, tb); > + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > + goto end; > + } > + > rt_mutex_init_proxy_locked(&rnp->boost_mtx.rtmutex, t); > raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > /* Lock only for side effect: boosts task t's priority. */ > rt_mutex_lock(&rnp->boost_mtx); > rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */ > rnp->n_boosts++; > - > +end: Nit: maybe rename the label to "skip_boost:" ? Code looks fine; however, out of curiosity; given that the higher priority tasks, in general, would exit their read side critical section quickly and boost the next blocking reader on exiting their read side section; do you see noticeable reduction in grace period timings with the change for certain type of workloads? Thanks Neeraj > return READ_ONCE(rnp->exp_tasks) != NULL || > READ_ONCE(rnp->boost_tasks) != NULL; > } ^ permalink raw reply [flat|nested] 8+ messages in thread
* RE: [PATCH] rcu: Only boost rcu reader tasks with lower priority than boost kthreads 2022-03-04 11:42 ` Neeraj Upadhyay @ 2022-03-07 2:03 ` Zhang, Qiang1 2022-03-07 19:15 ` Paul E. McKenney 0 siblings, 1 reply; 8+ messages in thread From: Zhang, Qiang1 @ 2022-03-07 2:03 UTC (permalink / raw) To: Neeraj Upadhyay, paulmck, frederic; +Cc: linux-kernel On 3/4/2022 2:56 PM, Zqiang wrote: > When RCU_BOOST is enabled, the boost kthreads will boosting readers > who are blocking a given grace period, if the current reader tasks > have a higher priority than boost kthreads(the boost kthreads priority > not always 1, if the kthread_prio is set), boosting is useless, skip > current task and select next task to boosting, reduce the time for a > given grace period. > > Signed-off-by: Zqiang <qiang1.zhang@intel.com> > --- > kernel/rcu/tree_plugin.h | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > index c3d212bc5338..d35b6da66bbd 100644 > --- a/kernel/rcu/tree_plugin.h > +++ b/kernel/rcu/tree_plugin.h > @@ -12,6 +12,7 @@ > */ > > #include "../locking/rtmutex_common.h" > +#include <linux/sched/deadline.h> > > static bool rcu_rdp_is_offloaded(struct rcu_data *rdp) > { > @@ -1065,13 +1066,20 @@ static int rcu_boost(struct rcu_node *rnp) > * section. > */ > t = container_of(tb, struct task_struct, rcu_node_entry); > + if (!rnp->exp_tasks && (dl_task(t) || t->prio <= current->prio)) { > + tb = rcu_next_node_entry(t, rnp); > + WRITE_ONCE(rnp->boost_tasks, tb); > + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > + goto end; > + } > + > rt_mutex_init_proxy_locked(&rnp->boost_mtx.rtmutex, t); > raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > /* Lock only for side effect: boosts task t's priority. */ > rt_mutex_lock(&rnp->boost_mtx); > rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */ > rnp->n_boosts++; > - > +end: >> >>Nit: maybe rename the label to "skip_boost:" ? >> >>Code looks fine; however, out of curiosity; given that the higher >>priority tasks, in general, would exit their read side critical section >>quickly and boost the next blocking reader on exiting their read side >>section; do you see noticeable reduction in grace period timings with >>the change for certain type of workloads? Thanks for feedback , In preempt-RT systems, there will be many real-time threads (most of them are created by users themselves ), their priority is higher or lower than boost kthreads (kthread_prio is set), for rt tasks with higher priority than boost kthreads, maybe it will exit read side critical quickly, maybe not, if it is preempted by a higher priority task, If try to boost operation, this increases the boosts kthread waiting time, as a result, the next blkd tasks cannot be boosted in time. of course, I don't deny it, there are also reasons that user priority setting is inappropriate. Thanks Zqiang >> >> >>Thanks >>Neeraj > return READ_ONCE(rnp->exp_tasks) != NULL || > READ_ONCE(rnp->boost_tasks) != NULL; > } ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] rcu: Only boost rcu reader tasks with lower priority than boost kthreads 2022-03-07 2:03 ` Zhang, Qiang1 @ 2022-03-07 19:15 ` Paul E. McKenney 2022-03-08 18:04 ` Uladzislau Rezki 0 siblings, 1 reply; 8+ messages in thread From: Paul E. McKenney @ 2022-03-07 19:15 UTC (permalink / raw) To: Zhang, Qiang1; +Cc: Neeraj Upadhyay, frederic, linux-kernel, rcu, bigeasy On Mon, Mar 07, 2022 at 02:03:17AM +0000, Zhang, Qiang1 wrote: > On 3/4/2022 2:56 PM, Zqiang wrote: > > When RCU_BOOST is enabled, the boost kthreads will boosting readers > > who are blocking a given grace period, if the current reader tasks > > have a higher priority than boost kthreads(the boost kthreads priority > > not always 1, if the kthread_prio is set), boosting is useless, skip > > current task and select next task to boosting, reduce the time for a > > given grace period. > > > > Signed-off-by: Zqiang <qiang1.zhang@intel.com> Adding to CC to get more eyes on this. I am not necessarily opposed to it, but I don't do that much RT work myself these days. Thanx, Paul > > --- > > kernel/rcu/tree_plugin.h | 10 +++++++++- > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > > index c3d212bc5338..d35b6da66bbd 100644 > > --- a/kernel/rcu/tree_plugin.h > > +++ b/kernel/rcu/tree_plugin.h > > @@ -12,6 +12,7 @@ > > */ > > > > #include "../locking/rtmutex_common.h" > > +#include <linux/sched/deadline.h> > > > > static bool rcu_rdp_is_offloaded(struct rcu_data *rdp) > > { > > @@ -1065,13 +1066,20 @@ static int rcu_boost(struct rcu_node *rnp) > > * section. > > */ > > t = container_of(tb, struct task_struct, rcu_node_entry); > > + if (!rnp->exp_tasks && (dl_task(t) || t->prio <= current->prio)) { > > + tb = rcu_next_node_entry(t, rnp); > > + WRITE_ONCE(rnp->boost_tasks, tb); > > + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > > + goto end; > > + } > > + > > rt_mutex_init_proxy_locked(&rnp->boost_mtx.rtmutex, t); > > raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > > /* Lock only for side effect: boosts task t's priority. */ > > rt_mutex_lock(&rnp->boost_mtx); > > rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */ > > rnp->n_boosts++; > > - > > +end: > >> > >>Nit: maybe rename the label to "skip_boost:" ? > >> > >>Code looks fine; however, out of curiosity; given that the higher > >>priority tasks, in general, would exit their read side critical section > >>quickly and boost the next blocking reader on exiting their read side > >>section; do you see noticeable reduction in grace period timings with > >>the change for certain type of workloads? > > Thanks for feedback , In preempt-RT systems, there will be many real-time threads (most > of them are created by users themselves ), their priority is higher or lower than boost kthreads > (kthread_prio is set), for rt tasks with higher priority than boost kthreads, maybe it will exit > read side critical quickly, maybe not, if it is preempted by a higher priority task, If try to boost operation, > this increases the boosts kthread waiting time, as a result, the next blkd tasks cannot be > boosted in time. of course, I don't deny it, there are also reasons that user priority setting is inappropriate. > > Thanks > Zqiang > > >> > >> > >>Thanks > >>Neeraj > > > return READ_ONCE(rnp->exp_tasks) != NULL || > > READ_ONCE(rnp->boost_tasks) != NULL; > > } ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] rcu: Only boost rcu reader tasks with lower priority than boost kthreads 2022-03-07 19:15 ` Paul E. McKenney @ 2022-03-08 18:04 ` Uladzislau Rezki 2022-03-08 18:13 ` Paul E. McKenney 2022-03-09 3:04 ` Zhang, Qiang1 0 siblings, 2 replies; 8+ messages in thread From: Uladzislau Rezki @ 2022-03-08 18:04 UTC (permalink / raw) To: Zhang, Qiang1 Cc: Zhang, Qiang1, paulmck, Neeraj Upadhyay, frederic, linux-kernel, rcu, bigeasy > On Mon, Mar 07, 2022 at 02:03:17AM +0000, Zhang, Qiang1 wrote: > > On 3/4/2022 2:56 PM, Zqiang wrote: > > > When RCU_BOOST is enabled, the boost kthreads will boosting readers > > > who are blocking a given grace period, if the current reader tasks > > > have a higher priority than boost kthreads(the boost kthreads priority > > > not always 1, if the kthread_prio is set), boosting is useless, skip > > > current task and select next task to boosting, reduce the time for a > > > given grace period. > > > > > > Signed-off-by: Zqiang <qiang1.zhang@intel.com> > > Adding to CC to get more eyes on this. I am not necessarily opposed to > it, but I don't do that much RT work myself these days. > > Thanx, Paul > > > > --- > > > kernel/rcu/tree_plugin.h | 10 +++++++++- > > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > > > index c3d212bc5338..d35b6da66bbd 100644 > > > --- a/kernel/rcu/tree_plugin.h > > > +++ b/kernel/rcu/tree_plugin.h > > > @@ -12,6 +12,7 @@ > > > */ > > > > > > #include "../locking/rtmutex_common.h" > > > +#include <linux/sched/deadline.h> > > > > > > static bool rcu_rdp_is_offloaded(struct rcu_data *rdp) > > > { > > > @@ -1065,13 +1066,20 @@ static int rcu_boost(struct rcu_node *rnp) > > > * section. > > > */ > > > t = container_of(tb, struct task_struct, rcu_node_entry); > > > + if (!rnp->exp_tasks && (dl_task(t) || t->prio <= current->prio)) { > > > + tb = rcu_next_node_entry(t, rnp); > > > + WRITE_ONCE(rnp->boost_tasks, tb); > > > + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > > > + goto end; > > > + } > > > + Why do you bypass the expedited grace period and boost any tasks anyway? Same way the expedited gp can be blocked by higher prior tasks SCHED_DEADLINE or SCHED_FIFO. Thanks! -- Vlad Rezki ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] rcu: Only boost rcu reader tasks with lower priority than boost kthreads 2022-03-08 18:04 ` Uladzislau Rezki @ 2022-03-08 18:13 ` Paul E. McKenney 2022-03-08 18:25 ` Uladzislau Rezki 2022-03-09 3:04 ` Zhang, Qiang1 1 sibling, 1 reply; 8+ messages in thread From: Paul E. McKenney @ 2022-03-08 18:13 UTC (permalink / raw) To: Uladzislau Rezki Cc: Zhang, Qiang1, Neeraj Upadhyay, frederic, linux-kernel, rcu, bigeasy, juri.lelli On Tue, Mar 08, 2022 at 07:04:21PM +0100, Uladzislau Rezki wrote: > > On Mon, Mar 07, 2022 at 02:03:17AM +0000, Zhang, Qiang1 wrote: > > > On 3/4/2022 2:56 PM, Zqiang wrote: > > > > When RCU_BOOST is enabled, the boost kthreads will boosting readers > > > > who are blocking a given grace period, if the current reader tasks > > > > have a higher priority than boost kthreads(the boost kthreads priority > > > > not always 1, if the kthread_prio is set), boosting is useless, skip > > > > current task and select next task to boosting, reduce the time for a > > > > given grace period. > > > > > > > > Signed-off-by: Zqiang <qiang1.zhang@intel.com> > > > > Adding to CC to get more eyes on this. I am not necessarily opposed to > > it, but I don't do that much RT work myself these days. > > > > Thanx, Paul > > > > > > --- > > > > kernel/rcu/tree_plugin.h | 10 +++++++++- > > > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > > > > index c3d212bc5338..d35b6da66bbd 100644 > > > > --- a/kernel/rcu/tree_plugin.h > > > > +++ b/kernel/rcu/tree_plugin.h > > > > @@ -12,6 +12,7 @@ > > > > */ > > > > > > > > #include "../locking/rtmutex_common.h" > > > > +#include <linux/sched/deadline.h> > > > > > > > > static bool rcu_rdp_is_offloaded(struct rcu_data *rdp) > > > > { > > > > @@ -1065,13 +1066,20 @@ static int rcu_boost(struct rcu_node *rnp) > > > > * section. > > > > */ > > > > t = container_of(tb, struct task_struct, rcu_node_entry); > > > > + if (!rnp->exp_tasks && (dl_task(t) || t->prio <= current->prio)) { > > > > + tb = rcu_next_node_entry(t, rnp); > > > > + WRITE_ONCE(rnp->boost_tasks, tb); > > > > + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > > > > + goto end; > > > > + } > > > > + > Why do you bypass the expedited grace period and boost any tasks anyway? > Same way the expedited gp can be blocked by higher prior tasks SCHED_DEADLINE > or SCHED_FIFO. Just to make sure that I understand... Are you pointing out that a SCHED_DEADLINE task might have exhausted its budget, so that boosting might nonetheless be helpful? Me, I honestly don't know what happens in that case, so I am just asking the question. And adding Juri on CC. ;-) Thanx, Paul ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] rcu: Only boost rcu reader tasks with lower priority than boost kthreads 2022-03-08 18:13 ` Paul E. McKenney @ 2022-03-08 18:25 ` Uladzislau Rezki 0 siblings, 0 replies; 8+ messages in thread From: Uladzislau Rezki @ 2022-03-08 18:25 UTC (permalink / raw) To: Paul E. McKenney Cc: Uladzislau Rezki, Zhang, Qiang1, Neeraj Upadhyay, frederic, linux-kernel, rcu, bigeasy, juri.lelli On Tue, Mar 08, 2022 at 10:13:55AM -0800, Paul E. McKenney wrote: > On Tue, Mar 08, 2022 at 07:04:21PM +0100, Uladzislau Rezki wrote: > > > On Mon, Mar 07, 2022 at 02:03:17AM +0000, Zhang, Qiang1 wrote: > > > > On 3/4/2022 2:56 PM, Zqiang wrote: > > > > > When RCU_BOOST is enabled, the boost kthreads will boosting readers > > > > > who are blocking a given grace period, if the current reader tasks > > > > > have a higher priority than boost kthreads(the boost kthreads priority > > > > > not always 1, if the kthread_prio is set), boosting is useless, skip > > > > > current task and select next task to boosting, reduce the time for a > > > > > given grace period. > > > > > > > > > > Signed-off-by: Zqiang <qiang1.zhang@intel.com> > > > > > > Adding to CC to get more eyes on this. I am not necessarily opposed to > > > it, but I don't do that much RT work myself these days. > > > > > > Thanx, Paul > > > > > > > > --- > > > > > kernel/rcu/tree_plugin.h | 10 +++++++++- > > > > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > > > > > index c3d212bc5338..d35b6da66bbd 100644 > > > > > --- a/kernel/rcu/tree_plugin.h > > > > > +++ b/kernel/rcu/tree_plugin.h > > > > > @@ -12,6 +12,7 @@ > > > > > */ > > > > > > > > > > #include "../locking/rtmutex_common.h" > > > > > +#include <linux/sched/deadline.h> > > > > > > > > > > static bool rcu_rdp_is_offloaded(struct rcu_data *rdp) > > > > > { > > > > > @@ -1065,13 +1066,20 @@ static int rcu_boost(struct rcu_node *rnp) > > > > > * section. > > > > > */ > > > > > t = container_of(tb, struct task_struct, rcu_node_entry); > > > > > + if (!rnp->exp_tasks && (dl_task(t) || t->prio <= current->prio)) { > > > > > + tb = rcu_next_node_entry(t, rnp); > > > > > + WRITE_ONCE(rnp->boost_tasks, tb); > > > > > + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > > > > > + goto end; > > > > > + } > > > > > + > > Why do you bypass the expedited grace period and boost any tasks anyway? > > Same way the expedited gp can be blocked by higher prior tasks SCHED_DEADLINE > > or SCHED_FIFO. > > Just to make sure that I understand... > > Are you pointing out that a SCHED_DEADLINE task might have exhausted > its budget, so that boosting might nonetheless be helpful? > SCHED_DEADLINE we can not preempt nor stop it somehow(highest prio class), it has some budget it makes use of. If it is in critical section then it will leave asap, i do not take into account here IRQs and so on. I do not see a reason to boost it. > > Me, I honestly don't know what happens in that case, so I am just asking > the question. And adding Juri on CC. ;-) > Juri should know more :) -- Vlad Rezki ^ permalink raw reply [flat|nested] 8+ messages in thread
* RE: [PATCH] rcu: Only boost rcu reader tasks with lower priority than boost kthreads 2022-03-08 18:04 ` Uladzislau Rezki 2022-03-08 18:13 ` Paul E. McKenney @ 2022-03-09 3:04 ` Zhang, Qiang1 1 sibling, 0 replies; 8+ messages in thread From: Zhang, Qiang1 @ 2022-03-09 3:04 UTC (permalink / raw) To: Uladzislau Rezki Cc: paulmck, Neeraj Upadhyay, frederic, linux-kernel, rcu, bigeasy > On Mon, Mar 07, 2022 at 02:03:17AM +0000, Zhang, Qiang1 wrote: > > On 3/4/2022 2:56 PM, Zqiang wrote: > > > When RCU_BOOST is enabled, the boost kthreads will boosting > > > readers who are blocking a given grace period, if the current > > > reader tasks have a higher priority than boost kthreads(the boost > > > kthreads priority not always 1, if the kthread_prio is set), > > > boosting is useless, skip current task and select next task to > > > boosting, reduce the time for a given grace period. > > > > > > Signed-off-by: Zqiang <qiang1.zhang@intel.com> > > Adding to CC to get more eyes on this. I am not necessarily opposed > to it, but I don't do that much RT work myself these days. > > Thanx, Paul > > > > --- > > > kernel/rcu/tree_plugin.h | 10 +++++++++- > > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > > > index c3d212bc5338..d35b6da66bbd 100644 > > > --- a/kernel/rcu/tree_plugin.h > > > +++ b/kernel/rcu/tree_plugin.h > > > @@ -12,6 +12,7 @@ > > > */ > > > > > > #include "../locking/rtmutex_common.h" > > > +#include <linux/sched/deadline.h> > > > > > > static bool rcu_rdp_is_offloaded(struct rcu_data *rdp) > > > { > > > @@ -1065,13 +1066,20 @@ static int rcu_boost(struct rcu_node *rnp) > > > * section. > > > */ > > > t = container_of(tb, struct task_struct, rcu_node_entry); > > > + if (!rnp->exp_tasks && (dl_task(t) || t->prio <= current->prio)) { > > > + tb = rcu_next_node_entry(t, rnp); > > > + WRITE_ONCE(rnp->boost_tasks, tb); > > > + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > > > + goto end; > > > + } > > > + >>>>Why do you bypass the expedited grace period and boost any tasks anyway? >>>>Same way the expedited gp can be blocked by higher prior tasks SCHED_DEADLINE or SCHED_FIFO. Thanks advice, it really ignores expedited grace period, may be should generate 'boost_exp_tasks' pointer to point 'rnp->exp_tasks', do the same thing as normal grace period. Thanks Zqiang >>>> >>>>Thanks! >>>> >>>>-- >>>>Vlad Rezki ^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2022-03-09 3:04 UTC | newest] Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-03-04 9:26 [PATCH] rcu: Only boost rcu reader tasks with lower priority than boost kthreads Zqiang 2022-03-04 11:42 ` Neeraj Upadhyay 2022-03-07 2:03 ` Zhang, Qiang1 2022-03-07 19:15 ` Paul E. McKenney 2022-03-08 18:04 ` Uladzislau Rezki 2022-03-08 18:13 ` Paul E. McKenney 2022-03-08 18:25 ` Uladzislau Rezki 2022-03-09 3:04 ` Zhang, Qiang1
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