6aa26565e6
- to isolate execution inside kernel we use a big kernel lock implemented as a spinlock - the lock is acquired asap after entering kernel mode and released as late as possible. Only one CPU as a time can execute the core kernel code - measurement son real hw show that the overhead of this lock is close to 0% of kernel time for the currnet system - the overhead of this lock may be as high as 45% of kernel time in virtual machines depending on the ratio between physical CPUs available and emulated CPUs. The performance degradation is significant
59 lines
1.6 KiB
C
59 lines
1.6 KiB
C
#ifndef __SMP_H__
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#define __SMP_H__
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#ifdef CONFIG_SMP
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#ifndef __ASSEMBLY__
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#include "kernel.h"
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#include "arch_smp.h"
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#include "spinlock.h"
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/* number of CPUs (execution strands in the system */
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EXTERN unsigned ncpus;
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/* Number of virtual strands per physical core */
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EXTERN unsigned ht_per_core;
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/* which cpu is bootstraping */
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EXTERN unsigned bsp_cpu_id;
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#define cpu_is_bsp(cpu) (bsp_cpu_id == cpu)
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/*
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* SMP initialization is largely architecture dependent and each architecture
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* must provide a method how to do it. If initiating SMP fails the function does
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* not report it. However it must put the system in such a state that it falls
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* back to a uniprocessor system. Although the uniprocessor configuration may be
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* suboptimal, the system must be able to run on the bootstrap processor as if
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* it was the only processor in the system
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*/
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_PROTOTYPE(void smp_init, (void));
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_PROTOTYPE(void smp_ipi_err_int, (void));
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_PROTOTYPE(void smp_ipi_spv_int, (void));
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_PROTOTYPE(void smp_ipi_sched, (void));
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_PROTOTYPE(void smp_ipi_dequeue, (void));
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_PROTOTYPE(void smp_ipi_stop, (void));
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_PROTOTYPE(void smp_ipi_reboot, (void));
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#define CPU_IS_BSP 1
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#define CPU_IS_READY 2
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struct cpu {
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u32_t flags;
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};
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EXTERN struct cpu cpus[CONFIG_MAX_CPUS];
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#define cpu_set_flag(cpu, flag) do { cpus[cpu].flags |= (flag); } while(0)
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#define cpu_clear_flag(cpu, flag) do { cpus[cpu].flags &= ~(flag); } while(0)
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#define cpu_test_flag(cpu, flag) (cpus[cpu].flags & (flag))
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#define cpu_is_ready(cpu) cpu_test_flag(cpu, CPU_IS_READY)
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SPINLOCK_DECLARE(big_kernel_lock)
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#endif /* __ASSEMBLY__ */
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#endif /* CONFIG_SMP */
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#endif /* __SMP_H__ */
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