| Message ID | 20220901131436.986-2-thunder.leizhen@huawei.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 98ec9849c71cdca6caa293a633b262a3d91babc5 |
| Headers | show |
| Series | rcu/nocb: Delete local variable 'need_rcu_nocb_mask' in rcu_init_nohz() | expand |
On 2022/9/1 21:14, Zhen Lei wrote: > In kernels built with either CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or > CONFIG_NO_HZ_FULL=y, additional CPUs must be added to rcu_nocb_mask. > Except that kernels booted without the rcu_nocbs= will not have > allocated rcu_nocb_mask. And the current rcu_init_nohz() function uses > its need_rcu_nocb_mask and offload_all local variables to track the > rcu_nocb and nohz_full state. > > But there is a much simpler approach, namely creating a cpumask pointer > to track the default and then using cpumask_available() to check the > rcu_nocb_mask state. This commit takes this approach, thereby simplifying > and shortening the rcu_init_nohz() function. > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Sorry, I forgot remove this "Signed-off-by". > Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> > --- > kernel/rcu/tree_nocb.h | 35 ++++++++++++----------------------- > 1 file changed, 12 insertions(+), 23 deletions(-) > > diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h > index 0a5f0ef41484518..8b6dceeabde0b4d 100644 > --- a/kernel/rcu/tree_nocb.h > +++ b/kernel/rcu/tree_nocb.h > @@ -1210,45 +1210,34 @@ EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload); > void __init rcu_init_nohz(void) > { > int cpu; > - bool need_rcu_nocb_mask = false; > - bool offload_all = false; > struct rcu_data *rdp; > - > -#if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) > - if (!rcu_state.nocb_is_setup) { > - need_rcu_nocb_mask = true; > - offload_all = true; > - } > -#endif /* #if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) */ > + const struct cpumask *cpumask = NULL; > > #if defined(CONFIG_NO_HZ_FULL) > - if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) { > - need_rcu_nocb_mask = true; > - offload_all = false; /* NO_HZ_FULL has its own mask. */ > - } > -#endif /* #if defined(CONFIG_NO_HZ_FULL) */ > + if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) > + cpumask = tick_nohz_full_mask; > +#endif > + > +#if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) > + if (!rcu_state.nocb_is_setup && !cpumask) > + cpumask = cpu_possible_mask; > +#endif > > - if (need_rcu_nocb_mask) { > + if (cpumask) { > if (!cpumask_available(rcu_nocb_mask)) { > if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { > pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); > return; > } > } > + > + cpumask_or(rcu_nocb_mask, rcu_nocb_mask, cpumask); > rcu_state.nocb_is_setup = true; > } > > if (!rcu_state.nocb_is_setup) > return; > > -#if defined(CONFIG_NO_HZ_FULL) > - if (tick_nohz_full_running) > - cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); > -#endif /* #if defined(CONFIG_NO_HZ_FULL) */ > - > - if (offload_all) > - cpumask_setall(rcu_nocb_mask); > - > if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { > pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n"); > cpumask_and(rcu_nocb_mask, cpu_possible_mask, >
On Thu, Sep 01, 2022 at 09:25:06PM +0800, Leizhen (ThunderTown) wrote: > > > On 2022/9/1 21:14, Zhen Lei wrote: > > In kernels built with either CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or > > CONFIG_NO_HZ_FULL=y, additional CPUs must be added to rcu_nocb_mask. > > Except that kernels booted without the rcu_nocbs= will not have > > allocated rcu_nocb_mask. And the current rcu_init_nohz() function uses > > its need_rcu_nocb_mask and offload_all local variables to track the > > rcu_nocb and nohz_full state. > > > > But there is a much simpler approach, namely creating a cpumask pointer > > to track the default and then using cpumask_available() to check the > > rcu_nocb_mask state. This commit takes this approach, thereby simplifying > > and shortening the rcu_init_nohz() function. > > > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > > Sorry, I forgot remove this "Signed-off-by". Not a problem, especially given that in view of my oversight on the previous version, I am going to let Frederic take first crack at this version. ;-) Thanx, Paul > > Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> > > --- > > kernel/rcu/tree_nocb.h | 35 ++++++++++++----------------------- > > 1 file changed, 12 insertions(+), 23 deletions(-) > > > > diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h > > index 0a5f0ef41484518..8b6dceeabde0b4d 100644 > > --- a/kernel/rcu/tree_nocb.h > > +++ b/kernel/rcu/tree_nocb.h > > @@ -1210,45 +1210,34 @@ EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload); > > void __init rcu_init_nohz(void) > > { > > int cpu; > > - bool need_rcu_nocb_mask = false; > > - bool offload_all = false; > > struct rcu_data *rdp; > > - > > -#if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) > > - if (!rcu_state.nocb_is_setup) { > > - need_rcu_nocb_mask = true; > > - offload_all = true; > > - } > > -#endif /* #if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) */ > > + const struct cpumask *cpumask = NULL; > > > > #if defined(CONFIG_NO_HZ_FULL) > > - if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) { > > - need_rcu_nocb_mask = true; > > - offload_all = false; /* NO_HZ_FULL has its own mask. */ > > - } > > -#endif /* #if defined(CONFIG_NO_HZ_FULL) */ > > + if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) > > + cpumask = tick_nohz_full_mask; > > +#endif > > + > > +#if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) > > + if (!rcu_state.nocb_is_setup && !cpumask) > > + cpumask = cpu_possible_mask; > > +#endif > > > > - if (need_rcu_nocb_mask) { > > + if (cpumask) { > > if (!cpumask_available(rcu_nocb_mask)) { > > if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { > > pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); > > return; > > } > > } > > + > > + cpumask_or(rcu_nocb_mask, rcu_nocb_mask, cpumask); > > rcu_state.nocb_is_setup = true; > > } > > > > if (!rcu_state.nocb_is_setup) > > return; > > > > -#if defined(CONFIG_NO_HZ_FULL) > > - if (tick_nohz_full_running) > > - cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); > > -#endif /* #if defined(CONFIG_NO_HZ_FULL) */ > > - > > - if (offload_all) > > - cpumask_setall(rcu_nocb_mask); > > - > > if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { > > pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n"); > > cpumask_and(rcu_nocb_mask, cpu_possible_mask, > > > > -- > Regards, > Zhen Lei
On Thu, Sep 01, 2022 at 09:14:35PM +0800, Zhen Lei wrote: > In kernels built with either CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or > CONFIG_NO_HZ_FULL=y, additional CPUs must be added to rcu_nocb_mask. > Except that kernels booted without the rcu_nocbs= will not have > allocated rcu_nocb_mask. And the current rcu_init_nohz() function uses > its need_rcu_nocb_mask and offload_all local variables to track the > rcu_nocb and nohz_full state. > > But there is a much simpler approach, namely creating a cpumask pointer > to track the default and then using cpumask_available() to check the > rcu_nocb_mask state. This commit takes this approach, thereby simplifying > and shortening the rcu_init_nohz() function. > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> > --- > kernel/rcu/tree_nocb.h | 35 ++++++++++++----------------------- > 1 file changed, 12 insertions(+), 23 deletions(-) > > diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h > index 0a5f0ef41484518..8b6dceeabde0b4d 100644 > --- a/kernel/rcu/tree_nocb.h > +++ b/kernel/rcu/tree_nocb.h > @@ -1210,45 +1210,34 @@ EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload); > void __init rcu_init_nohz(void) > { > int cpu; > - bool need_rcu_nocb_mask = false; > - bool offload_all = false; > struct rcu_data *rdp; > - > -#if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) > - if (!rcu_state.nocb_is_setup) { > - need_rcu_nocb_mask = true; > - offload_all = true; > - } > -#endif /* #if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) */ > + const struct cpumask *cpumask = NULL; > > #if defined(CONFIG_NO_HZ_FULL) > - if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) { > - need_rcu_nocb_mask = true; > - offload_all = false; /* NO_HZ_FULL has its own mask. */ > - } > -#endif /* #if defined(CONFIG_NO_HZ_FULL) */ > + if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) > + cpumask = tick_nohz_full_mask; > +#endif > + > +#if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) > + if (!rcu_state.nocb_is_setup && !cpumask) > + cpumask = cpu_possible_mask; > +#endif Good, and it can even use a simple condition: if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) && !rcu_state.nocb_is_setup && !cpumask) cpumask = cpu_possible_mask; Acked-by: Frederic Weisbecker <frederic@kernel.org> > > - if (need_rcu_nocb_mask) { > + if (cpumask) { > if (!cpumask_available(rcu_nocb_mask)) { > if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { > pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); > return; > } > } > + > + cpumask_or(rcu_nocb_mask, rcu_nocb_mask, cpumask); > rcu_state.nocb_is_setup = true; > } > > if (!rcu_state.nocb_is_setup) > return; > > -#if defined(CONFIG_NO_HZ_FULL) > - if (tick_nohz_full_running) > - cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); > -#endif /* #if defined(CONFIG_NO_HZ_FULL) */ > - > - if (offload_all) > - cpumask_setall(rcu_nocb_mask); > - > if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { > pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n"); > cpumask_and(rcu_nocb_mask, cpu_possible_mask, > -- > 2.25.1 >
On 2022/9/7 19:04, Frederic Weisbecker wrote: > On Thu, Sep 01, 2022 at 09:14:35PM +0800, Zhen Lei wrote: >> In kernels built with either CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or >> CONFIG_NO_HZ_FULL=y, additional CPUs must be added to rcu_nocb_mask. >> Except that kernels booted without the rcu_nocbs= will not have >> allocated rcu_nocb_mask. And the current rcu_init_nohz() function uses >> its need_rcu_nocb_mask and offload_all local variables to track the >> rcu_nocb and nohz_full state. >> >> But there is a much simpler approach, namely creating a cpumask pointer >> to track the default and then using cpumask_available() to check the >> rcu_nocb_mask state. This commit takes this approach, thereby simplifying >> and shortening the rcu_init_nohz() function. >> >> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> >> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> >> --- >> kernel/rcu/tree_nocb.h | 35 ++++++++++++----------------------- >> 1 file changed, 12 insertions(+), 23 deletions(-) >> >> diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h >> index 0a5f0ef41484518..8b6dceeabde0b4d 100644 >> --- a/kernel/rcu/tree_nocb.h >> +++ b/kernel/rcu/tree_nocb.h >> @@ -1210,45 +1210,34 @@ EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload); >> void __init rcu_init_nohz(void) >> { >> int cpu; >> - bool need_rcu_nocb_mask = false; >> - bool offload_all = false; >> struct rcu_data *rdp; >> - >> -#if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) >> - if (!rcu_state.nocb_is_setup) { >> - need_rcu_nocb_mask = true; >> - offload_all = true; >> - } >> -#endif /* #if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) */ >> + const struct cpumask *cpumask = NULL; >> >> #if defined(CONFIG_NO_HZ_FULL) >> - if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) { >> - need_rcu_nocb_mask = true; >> - offload_all = false; /* NO_HZ_FULL has its own mask. */ >> - } >> -#endif /* #if defined(CONFIG_NO_HZ_FULL) */ >> + if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) >> + cpumask = tick_nohz_full_mask; >> +#endif >> + >> +#if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) >> + if (!rcu_state.nocb_is_setup && !cpumask) >> + cpumask = cpu_possible_mask; >> +#endif > > Good, and it can even use a simple condition: > > if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) && > !rcu_state.nocb_is_setup && !cpumask) > cpumask = cpu_possible_mask; Okay, I'll revise it in v7. > > > Acked-by: Frederic Weisbecker <frederic@kernel.org> > > >> >> - if (need_rcu_nocb_mask) { >> + if (cpumask) { >> if (!cpumask_available(rcu_nocb_mask)) { >> if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { >> pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); >> return; >> } >> } >> + >> + cpumask_or(rcu_nocb_mask, rcu_nocb_mask, cpumask); >> rcu_state.nocb_is_setup = true; >> } >> >> if (!rcu_state.nocb_is_setup) >> return; >> >> -#if defined(CONFIG_NO_HZ_FULL) >> - if (tick_nohz_full_running) >> - cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); >> -#endif /* #if defined(CONFIG_NO_HZ_FULL) */ >> - >> - if (offload_all) >> - cpumask_setall(rcu_nocb_mask); >> - >> if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { >> pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n"); >> cpumask_and(rcu_nocb_mask, cpu_possible_mask, >> -- >> 2.25.1 >> > . >
diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index 0a5f0ef41484518..8b6dceeabde0b4d 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -1210,45 +1210,34 @@ EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload); void __init rcu_init_nohz(void) { int cpu; - bool need_rcu_nocb_mask = false; - bool offload_all = false; struct rcu_data *rdp; - -#if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) - if (!rcu_state.nocb_is_setup) { - need_rcu_nocb_mask = true; - offload_all = true; - } -#endif /* #if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) */ + const struct cpumask *cpumask = NULL; #if defined(CONFIG_NO_HZ_FULL) - if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) { - need_rcu_nocb_mask = true; - offload_all = false; /* NO_HZ_FULL has its own mask. */ - } -#endif /* #if defined(CONFIG_NO_HZ_FULL) */ + if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) + cpumask = tick_nohz_full_mask; +#endif + +#if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) + if (!rcu_state.nocb_is_setup && !cpumask) + cpumask = cpu_possible_mask; +#endif - if (need_rcu_nocb_mask) { + if (cpumask) { if (!cpumask_available(rcu_nocb_mask)) { if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); return; } } + + cpumask_or(rcu_nocb_mask, rcu_nocb_mask, cpumask); rcu_state.nocb_is_setup = true; } if (!rcu_state.nocb_is_setup) return; -#if defined(CONFIG_NO_HZ_FULL) - if (tick_nohz_full_running) - cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); -#endif /* #if defined(CONFIG_NO_HZ_FULL) */ - - if (offload_all) - cpumask_setall(rcu_nocb_mask); - if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n"); cpumask_and(rcu_nocb_mask, cpu_possible_mask,