diff options
| author | Shrikanth Hegde <sshegde@linux.ibm.com> | 2025-02-11 00:13:34 +0530 |
|---|---|---|
| committer | Madhavan Srinivasan <maddy@linux.ibm.com> | 2025-04-16 22:30:22 +0530 |
| commit | 6ad7751537e884c45b5340a4a24c25535f0d9c13 (patch) | |
| tree | 47f78f2c38487d65e69a0e2cc19180840c1a24c4 | |
| parent | 28affd477bf53ddd89b16e4dd7bacf64a1eaf116 (diff) | |
powerpc: enable dynamic preemption
Once the lazy preemption is supported, it would be desirable to change
the preemption models at runtime. So add support for dynamic preemption
using DYNAMIC_KEY.
::Tested lightly on Power10 LPAR
Performance numbers indicate that, preempt=none(no dynamic) and
preempt=none(dynamic) are close.
cat /sys/kernel/debug/sched/preempt
(none) voluntary full lazy
perf stat -e probe:__cond_resched -a sleep 1
Performance counter stats for 'system wide':
1,253 probe:__cond_resched
echo full > /sys/kernel/debug/sched/preempt
cat /sys/kernel/debug/sched/preempt
none voluntary (full) lazy
perf stat -e probe:__cond_resched -a sleep 1
Performance counter stats for 'system wide':
0 probe:__cond_resched
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250210184334.567383-2-sshegde@linux.ibm.com
| -rw-r--r-- | arch/powerpc/Kconfig | 1 | ||||
| -rw-r--r-- | arch/powerpc/include/asm/preempt.h | 16 | ||||
| -rw-r--r-- | arch/powerpc/kernel/interrupt.c | 6 | ||||
| -rw-r--r-- | arch/powerpc/lib/vmx-helper.c | 2 |
4 files changed, 23 insertions, 2 deletions
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 6722625a406a..2519fc3538c6 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -277,6 +277,7 @@ config PPC select HAVE_PERF_EVENTS_NMI if PPC64 select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP + select HAVE_PREEMPT_DYNAMIC_KEY select HAVE_RETHOOK if KPROBES select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_RELIABLE_STACKTRACE diff --git a/arch/powerpc/include/asm/preempt.h b/arch/powerpc/include/asm/preempt.h new file mode 100644 index 000000000000..000e2b9681f3 --- /dev/null +++ b/arch/powerpc/include/asm/preempt.h @@ -0,0 +1,16 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_POWERPC_PREEMPT_H +#define __ASM_POWERPC_PREEMPT_H + +#include <asm-generic/preempt.h> + +#if defined(CONFIG_PREEMPT_DYNAMIC) +#include <linux/jump_label.h> +DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched); +#define need_irq_preemption() \ + (static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched)) +#else +#define need_irq_preemption() (IS_ENABLED(CONFIG_PREEMPTION)) +#endif + +#endif /* __ASM_POWERPC_PREEMPT_H */ diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c index 8f4acc55407b..e0c681d0b076 100644 --- a/arch/powerpc/kernel/interrupt.c +++ b/arch/powerpc/kernel/interrupt.c @@ -25,6 +25,10 @@ unsigned long global_dbcr0[NR_CPUS]; #endif +#if defined(CONFIG_PREEMPT_DYNAMIC) +DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched); +#endif + #ifdef CONFIG_PPC_BOOK3S_64 DEFINE_STATIC_KEY_FALSE(interrupt_exit_not_reentrant); static inline bool exit_must_hard_disable(void) @@ -396,7 +400,7 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs) /* Returning to a kernel context with local irqs enabled. */ WARN_ON_ONCE(!(regs->msr & MSR_EE)); again: - if (IS_ENABLED(CONFIG_PREEMPTION)) { + if (need_irq_preemption()) { /* Return to preemptible kernel context */ if (unlikely(read_thread_flags() & _TIF_NEED_RESCHED)) { if (preempt_count() == 0) diff --git a/arch/powerpc/lib/vmx-helper.c b/arch/powerpc/lib/vmx-helper.c index 58ed6bd613a6..54340912398f 100644 --- a/arch/powerpc/lib/vmx-helper.c +++ b/arch/powerpc/lib/vmx-helper.c @@ -45,7 +45,7 @@ int exit_vmx_usercopy(void) * set and we are preemptible. The hack here is to schedule a * decrementer to fire here and reschedule for us if necessary. */ - if (IS_ENABLED(CONFIG_PREEMPTION) && need_resched()) + if (need_irq_preemption() && need_resched()) set_dec(1); return 0; } |