Messages in this thread Patch in this message | | | From | Alexey Dobriyan <> | Subject | [PATCH] cpu: memoise number of possible cpus | Date | Thu, 18 Apr 2024 07:19:27 +0300 |
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cpu_possible_mask is fixed after boot, so it makes sense to calculate number of possible cpus to a) make num_possible_cpus() faster (distros ship with _large_ NR_CPUS), b) unscrew codegen elsewhere replacing function call with simple memory load.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> --- include/linux/cpumask.h | 3 ++- init/main.c | 3 +++ kernel/cpu.c | 3 +++ 3 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index 04536a29f10f..a98843ca6131 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -1106,7 +1106,8 @@ static __always_inline unsigned int num_online_cpus(void) { return raw_atomic_read(&__num_online_cpus); } -#define num_possible_cpus() cpumask_weight(cpu_possible_mask) +extern unsigned int num_possible_cpus; +#define num_possible_cpus() num_possible_cpus #define num_present_cpus() cpumask_weight(cpu_present_mask) #define num_active_cpus() cpumask_weight(cpu_active_mask) diff --git a/init/main.c b/init/main.c index 881f6230ee59..fe0291b44d78 100644 --- a/init/main.c +++ b/init/main.c @@ -904,6 +904,9 @@ void start_kernel(void) setup_boot_config(); setup_command_line(command_line); setup_nr_cpu_ids(); +#if NR_CPUS > 1 + num_possible_cpus = cpumask_weight(cpu_possible_mask); +#endif setup_per_cpu_areas(); smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */ boot_cpu_hotplug_init(); diff --git a/kernel/cpu.c b/kernel/cpu.c index 07ad53b7f119..4a75f95fec82 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -3106,6 +3106,9 @@ EXPORT_SYMBOL_GPL(cpu_bit_bitmap); const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL; EXPORT_SYMBOL(cpu_all_bits); +unsigned int num_possible_cpus __ro_after_init = 1; +EXPORT_SYMBOL(num_possible_cpus); + #ifdef CONFIG_INIT_ALL_POSSIBLE struct cpumask __cpu_possible_mask __ro_after_init = {CPU_BITS_ALL}; -- 2.43.2
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