Messages in this thread Patch in this message | | | Date | Thu, 19 Dec 2019 11:35:17 -0500 | From | Steven Rostedt <> | Subject | [PATCH] sched: Force the address order of each sched class descriptor |
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From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
[ Kirill, feel free to include this patch with yours ]
In order to make a micro optimization in pick_next_task(), the order of the sched class descriptor address must be in the same order as their priority to each other. That is:
&idle_sched_class < &fair_sched_class < &rt_sched_class < &dl_sched_class < &stop_sched_class
In order to guarantee this order of the sched class descriptors, add each one into their own data section and force the order in the linker script.
Link: https://lore.kernel.org/r/157675913272.349305.8936736338884044103.stgit@localhost.localdomain Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> --- include/asm-generic/vmlinux.lds.h | 13 +++++++++++++ kernel/sched/deadline.c | 3 ++- kernel/sched/fair.c | 3 ++- kernel/sched/idle.c | 3 ++- kernel/sched/rt.c | 3 ++- kernel/sched/stop_task.c | 3 ++- 6 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index e00f41aa8ec4..7e8b02fdcf3f 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -108,6 +108,18 @@ #define SBSS_MAIN .sbss #endif +/* + * The order of the sched class addresses are important, as they are + * used to determine the order of the priority of each sched class in + * relation to each other. + */ +#define SCHED_DATA \ + *(__idle_sched_class) \ + *(__fair_sched_class) \ + *(__rt_sched_class) \ + *(__dl_sched_class) \ + *(__stop_sched_class) + /* * Align to a 32 byte boundary equal to the * alignment gcc 4.5 uses for a struct @@ -308,6 +320,7 @@ #define DATA_DATA \ *(.xiptext) \ *(DATA_MAIN) \ + SCHED_DATA \ *(.ref.data) \ *(.data..shared_aligned) /* percpu related */ \ MEM_KEEP(init.data*) \ diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 43323f875cb9..5abdbe569f93 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2428,7 +2428,8 @@ static void prio_changed_dl(struct rq *rq, struct task_struct *p, } } -const struct sched_class dl_sched_class = { +const struct sched_class dl_sched_class + __attribute__((section("__dl_sched_class"))) = { .next = &rt_sched_class, .enqueue_task = enqueue_task_dl, .dequeue_task = dequeue_task_dl, diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 08a233e97a01..e745fe0e0cd3 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10745,7 +10745,8 @@ static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task /* * All the scheduling class methods: */ -const struct sched_class fair_sched_class = { +const struct sched_class fair_sched_class + __attribute__((section("__fair_sched_class"))) = { .next = &idle_sched_class, .enqueue_task = enqueue_task_fair, .dequeue_task = dequeue_task_fair, diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index ffa959e91227..700a9c826f0e 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -454,7 +454,8 @@ static void update_curr_idle(struct rq *rq) /* * Simple, special scheduling class for the per-CPU idle tasks: */ -const struct sched_class idle_sched_class = { +const struct sched_class idle_sched_class + __attribute__((section("__idle_sched_class"))) = { /* .next is NULL */ /* no enqueue/yield_task for idle tasks */ diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index e591d40fd645..5d3f9bcddaeb 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2354,7 +2354,8 @@ static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task) return 0; } -const struct sched_class rt_sched_class = { +const struct sched_class rt_sched_class + __attribute__((section("__rt_sched_class"))) = { .next = &fair_sched_class, .enqueue_task = enqueue_task_rt, .dequeue_task = dequeue_task_rt, diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c index 4c9e9975684f..03bc7530ff75 100644 --- a/kernel/sched/stop_task.c +++ b/kernel/sched/stop_task.c @@ -115,7 +115,8 @@ static void update_curr_stop(struct rq *rq) /* * Simple, special scheduling class for the per-CPU stop tasks: */ -const struct sched_class stop_sched_class = { +const struct sched_class stop_sched_class + __attribute__((section("__stop_sched_class"))) = { .next = &dl_sched_class, .enqueue_task = enqueue_task_stop, -- 2.20.1
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