On Mon, Dec 05, 2005 at 04:35:27PM +0530, Srivatsa Vaddagiri wrote:
> This patch forces RCU torture threads off various CPUs in the system
> allowing them to become idle and go tickless. Meant to test support for
> such tickless idle CPU in RCU.
Good addition, works on 2.6.15 on x86 and ppc64.
Thanx, Paul
Acked-by: Paul E. McKenney <[email protected]>
> Signed-off-by : Srivatsa Vaddagiri <[email protected]>
>
> ---
>
> linux-2.6.15-rc5-mm1-root/kernel/rcutorture.c | 89 +++++++++++++++++++++++++-
> 1 files changed, 87 insertions(+), 2 deletions(-)
>
> diff -puN kernel/rcutorture.c~rcutorture kernel/rcutorture.c
> --- linux-2.6.15-rc5-mm1/kernel/rcutorture.c~rcutorture 2005-12-05 15:33:34.000000000 +0530
> +++ linux-2.6.15-rc5-mm1-root/kernel/rcutorture.c 2005-12-05 15:33:42.000000000 +0530
> @@ -51,6 +51,8 @@ static int nreaders = -1; /* # reader th
> static int stat_interval = 0; /* Interval between stats, in seconds. */
> /* Defaults to "only at end of test". */
> static int verbose = 0; /* Print more debug info. */
> +static int test_no_idle_hz = 0; /* Test RCU's support for tickless idle CPUs. */
> +static int shuffle_interval = 5; /* Interval between shuffles (in sec)*/
>
> MODULE_PARM(nreaders, "i");
> MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
> @@ -58,6 +60,10 @@ MODULE_PARM(stat_interval, "i");
> MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
> MODULE_PARM(verbose, "i");
> MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
> +MODULE_PARM(test_no_idle_hz, "i");
> +MODULE_PARM_DESC(test_no_idle_hz, "Test support for tickless idle CPUs");
> +MODULE_PARM(shuffle_interval, "i");
> +MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
> #define TORTURE_FLAG "rcutorture: "
> #define PRINTK_STRING(s) \
> do { printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
> @@ -72,6 +78,7 @@ static int nrealreaders;
> static struct task_struct *writer_task;
> static struct task_struct **reader_tasks;
> static struct task_struct *stats_task;
> +static struct task_struct *shuffler_task;
>
> #define RCU_TORTURE_PIPE_LEN 10
>
> @@ -375,12 +382,77 @@ rcu_torture_stats(void *arg)
> return 0;
> }
>
> +int rcu_idle_cpu; /* Force all torture tasks off this CPU */
> +
> +/* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
> + * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
> + */
> +void rcu_torture_shuffle_tasks(void)
> +{
> + cpumask_t tmp_mask = CPU_MASK_ALL;
> + int i;
> +
> + lock_cpu_hotplug();
> +
> + /* No point in shuffling if there is only one online CPU (ex: UP) */
> + if (num_online_cpus() == 1) {
> + unlock_cpu_hotplug();
> + return;
> + }
> +
> + if (rcu_idle_cpu != -1)
> + cpu_clear(rcu_idle_cpu, tmp_mask);
> +
> + set_cpus_allowed(current, tmp_mask);
> +
> + if (reader_tasks != NULL) {
> + for (i = 0; i < nrealreaders; i++)
> + if (reader_tasks[i])
> + set_cpus_allowed(reader_tasks[i], tmp_mask);
> + }
> +
> + if (writer_task)
> + set_cpus_allowed(writer_task, tmp_mask);
> +
> + if (stats_task)
> + set_cpus_allowed(stats_task, tmp_mask);
> +
> + if (rcu_idle_cpu == -1)
> + rcu_idle_cpu = num_online_cpus() - 1;
> + else
> + rcu_idle_cpu--;
> +
> + unlock_cpu_hotplug();
> +}
> +
> +/* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
> + * system to become idle at a time and cut off its timer ticks. This is meant
> + * to test the support for such tickless idle CPU in RCU.
> + */
> +static int
> +rcu_torture_shuffle(void *arg)
> +{
> + VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
> + do {
> + schedule_timeout_interruptible(shuffle_interval * HZ);
> + rcu_torture_shuffle_tasks();
> + } while (!kthread_should_stop());
> + VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
> + return 0;
> +}
> +
> static void
> rcu_torture_cleanup(void)
> {
> int i;
>
> fullstop = 1;
> + if (shuffler_task != NULL) {
> + VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
> + kthread_stop(shuffler_task);
> + }
> + shuffler_task = NULL;
> +
> if (writer_task != NULL) {
> VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
> kthread_stop(writer_task);
> @@ -430,8 +502,9 @@ rcu_torture_init(void)
> else
> nrealreaders = 2 * num_online_cpus();
> printk(KERN_ALERT TORTURE_FLAG
> - "--- Start of test: nreaders=%d stat_interval=%d verbose=%d\n",
> - nrealreaders, stat_interval, verbose);
> + "--- Start of test: nreaders=%d stat_interval=%d verbose=%d test_no_idle_hz=%d shuffle_interval = %d\n",
> + nrealreaders, stat_interval, verbose, test_no_idle_hz,
> + shuffle_interval);
> fullstop = 0;
>
> /* Set up the freelist. */
> @@ -501,6 +574,18 @@ rcu_torture_init(void)
> goto unwind;
> }
> }
> + if (test_no_idle_hz) {
> + rcu_idle_cpu = num_online_cpus() - 1;
> + /* Create the shuffler thread */
> + shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
> + "rcu_torture_shuffle");
> + if (IS_ERR(shuffler_task)) {
> + firsterr = PTR_ERR(shuffler_task);
> + VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
> + shuffler_task = NULL;
> + goto unwind;
> + }
> + }
> return 0;
>
> unwind:
>
> _
> --
>
>
> Thanks and Regards,
> Srivatsa Vaddagiri,
> Linux Technology Center,
> IBM Software Labs,
> Bangalore, INDIA - 560017
>
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