On Wed, Jun 27, 2007 at 03:36:34PM -0400, Steven Rostedt wrote:
> I believe this was originally done by Dipankar Sarma. I pulled these
> changes from the -rt kernel.
>
> For better preformance, RCU should use a softirq instead of a
> tasklet.
Acked-by: Paul E. McKenney <[email protected]>
Tested-by: Paul E. McKenney <[email protected]>
Tested with both kernbench and rcutorture on i386, x86_64, and ppc64.
Thanx, Paul
> From: Dipankar Sarma <[email protected]>
> Signed-off-by: Steven Rostedt <[email protected]>
>
> Index: linux-2.6-test/include/linux/interrupt.h
> ===================================================================
> --- linux-2.6-test.orig/include/linux/interrupt.h
> +++ linux-2.6-test/include/linux/interrupt.h
> @@ -245,6 +245,9 @@ enum
> #ifdef CONFIG_HIGH_RES_TIMERS
> HRTIMER_SOFTIRQ,
> #endif
> + RCU_SOFTIRQ, /* Preferable RCU should always be the last softirq */
> + /* Entries after this are ignored in split softirq mode */
> + MAX_SOFTIRQ,
> };
>
> /* softirq mask and active fields moved to irq_cpustat_t in
> Index: linux-2.6-test/kernel/rcupdate.c
> ===================================================================
> --- linux-2.6-test.orig/kernel/rcupdate.c
> +++ linux-2.6-test/kernel/rcupdate.c
> @@ -67,7 +67,6 @@ DEFINE_PER_CPU(struct rcu_data, rcu_data
> DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L };
>
> /* Fake initialization required by compiler */
> -static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL};
> static int blimit = 10;
> static int qhimark = 10000;
> static int qlowmark = 100;
> @@ -253,7 +252,7 @@ static void rcu_do_batch(struct rcu_data
> if (!rdp->donelist)
> rdp->donetail = &rdp->donelist;
> else
> - tasklet_schedule(&per_cpu(rcu_tasklet, rdp->cpu));
> + raise_softirq(RCU_SOFTIRQ);
> }
>
> /*
> @@ -405,7 +404,6 @@ static void rcu_offline_cpu(int cpu)
> &per_cpu(rcu_bh_data, cpu));
> put_cpu_var(rcu_data);
> put_cpu_var(rcu_bh_data);
> - tasklet_kill_immediate(&per_cpu(rcu_tasklet, cpu), cpu);
> }
>
> #else
> @@ -417,7 +415,7 @@ static void rcu_offline_cpu(int cpu)
> #endif
>
> /*
> - * This does the RCU processing work from tasklet context.
> + * This does the RCU processing work from softirq context.
> */
> static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
> struct rcu_data *rdp)
> @@ -462,7 +460,7 @@ static void __rcu_process_callbacks(stru
> rcu_do_batch(rdp);
> }
>
> -static void rcu_process_callbacks(unsigned long unused)
> +static void rcu_process_callbacks(struct softirq_action *unused)
> {
> __rcu_process_callbacks(&rcu_ctrlblk, &__get_cpu_var(rcu_data));
> __rcu_process_callbacks(&rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data));
> @@ -526,7 +524,7 @@ void rcu_check_callbacks(int cpu, int us
> rcu_bh_qsctr_inc(cpu);
> } else if (!in_softirq())
> rcu_bh_qsctr_inc(cpu);
> - tasklet_schedule(&per_cpu(rcu_tasklet, cpu));
> + raise_softirq(RCU_SOFTIRQ);
> }
>
> static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp,
> @@ -549,7 +547,7 @@ static void __devinit rcu_online_cpu(int
>
> rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp);
> rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp);
> - tasklet_init(&per_cpu(rcu_tasklet, cpu), rcu_process_callbacks, 0UL);
> + open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
> }
>
> static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
>
> --
-
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