Re: [PATCH v7 06/23] sched: Add CONFIG_SCHED_PROXY_EXEC & boot argument to enable/disable

Metin Kaya
2023-12-28T15:06:18Z

On 20/12/2023 12:18 am, John Stultz wrote:
> Add a CONFIG_SCHED_PROXY_EXEC option, along with a boot argument
> sched_prox_exec= that can be used to disable the feature at boot
> time if CONFIG_SCHED_PROXY_EXEC was enabled.
>
> Cc: Joel Fernandes <joelaf@google.com>
> Cc: Qais Yousef <qyousef@google.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Vincent Guittot <vincent.guittot@linaro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
> Cc: Valentin Schneider <vschneid@redhat.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ben Segall <bsegall@google.com>
> Cc: Zimuzo Ezeozue <zezeozue@google.com>
> Cc: Youssef Esmat <youssefesmat@google.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Waiman Long <longman@redhat.com>
> Cc: Boqun Feng <boqun.feng@gmail.com>
> Cc: "Paul E. McKenney" <paulmck@kernel.org>
> Cc: Metin Kaya <Metin.Kaya@arm.com>
> Cc: Xuewen Yan <xuewen.yan94@gmail.com>
> Cc: K Prateek Nayak <kprateek.nayak@amd.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: kernel-team@android.com
> Signed-off-by: John Stultz <jstultz@google.com>
> ---
> v7:
> * Switch to CONFIG_SCHED_PROXY_EXEC/sched_proxy_exec= as
> suggested by Metin Kaya.
> * Switch boot arg from =disable/enable to use kstrtobool(),
> which supports =yes|no|1|0|true|false|on|off, as also
> suggested by Metin Kaya, and print a message when a boot
> argument is used.
> ---
> .../admin-guide/kernel-parameters.txt | 5 ++++
> include/linux/sched.h | 13 +++++++++
> init/Kconfig | 7 +++++
> kernel/sched/core.c | 29 +++++++++++++++++++
> 4 files changed, 54 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 65731b060e3f..cc64393b913f 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -5714,6 +5714,11 @@
> sa1100ir [NET]
> See drivers/net/irda/sa1100_ir.c.
>
> + sched_proxy_exec= [KNL]
> + Enables or disables "proxy execution" style
> + solution to mutex based priority inversion.
> + Format: <bool>
> +
> sched_verbose [KNL] Enables verbose scheduler debug messages.
>
> schedstats= [KNL,X86] Enable or disable scheduled statistics.
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index bfe8670f99a1..880af1c3097d 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1566,6 +1566,19 @@ struct task_struct {
> */
> };
>
> +#ifdef CONFIG_SCHED_PROXY_EXEC
> +DECLARE_STATIC_KEY_TRUE(__sched_proxy_exec);
> +static inline bool sched_proxy_exec(void)
> +{
> + return static_branch_likely(&__sched_proxy_exec);
> +}
> +#else
> +static inline bool sched_proxy_exec(void)
> +{
> + return false;
> +}
> +#endif
> +
> static inline struct pid *task_pid(struct task_struct *task)
> {
> return task->thread_pid;
> diff --git a/init/Kconfig b/init/Kconfig
> index 9ffb103fc927..c5a759b6366a 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -908,6 +908,13 @@ config NUMA_BALANCING_DEFAULT_ENABLED
> If set, automatic NUMA balancing will be enabled if running on a NUMA
> machine.
>
> +config SCHED_PROXY_EXEC
> + bool "Proxy Execution"
> + default n
> + help
> + This option enables proxy execution, a mechanism for mutex owning
> + tasks to inherit the scheduling context of higher priority waiters.
> +

Should `SCHED_PROXY_EXEC` config option be under `Scheduler features` menu?

> menuconfig CGROUPS
> bool "Control Group support"
> select KERNFS
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 4e46189d545d..e06558fb08aa 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -117,6 +117,35 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(sched_compute_energy_tp);
>
> DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
>
> +#ifdef CONFIG_SCHED_PROXY_EXEC
> +DEFINE_STATIC_KEY_TRUE(__sched_proxy_exec);
> +static int __init setup_proxy_exec(char *str)
> +{
> + bool proxy_enable;
> +
> + if (kstrtobool(str, &proxy_enable)) {
> + pr_warn("Unable to parse sched_proxy_exec=\n");
> + return 0;
> + }
> +
> + if (proxy_enable) {
> + pr_info("sched_proxy_exec enabled via boot arg\n");
> + static_branch_enable(&__sched_proxy_exec);
> + } else {
> + pr_info("sched_proxy_exec disabled via boot arg\n");
> + static_branch_disable(&__sched_proxy_exec);
> + }
> + return 1;
> +}
> +#else
> +static int __init setup_proxy_exec(char *str)
> +{
> + pr_warn("CONFIG_SCHED_PROXY_EXEC=n, so it cannot be enabled or disabled at boottime\n");
> + return 0;
> +}
> +#endif
> +__setup("sched_proxy_exec=", setup_proxy_exec);
> +
> #ifdef CONFIG_SCHED_DEBUG
> /*
> * Debugging: various feature bits