minix/kernel/smp.c

#include "smp.h"

unsigned ncpus;
unsigned ht_per_core;
unsigned bsp_cpu_id;

struct cpu cpus[CONFIG_MAX_CPUS];

SPINLOCK_DEFINE(big_kernel_lock)
SMP - We boot APs - kernel detects CPUs by searching ACPI tables for local apic nodes - each CPU has its own TSS that points to its own stack. All cpus boot on the same boot stack (in sequence) but switch to its private stack as soon as they can. - final booting code in main() placed in bsp_finish_booting() which is executed only after the BSP switches to its final stack - apic functions to send startup interrupts - assembler functions to handle CPU features not needed for single cpu mode like memory barries, HT detection etc. - new files kernel/smp.[ch], kernel/arch/i386/arch_smp.c and kernel/arch/i386/include/arch_smp.h - 16-bit trampoline code for the APs. It is executed by each AP after receiving startup IPIs it brings up the CPUs to 32bit mode and let them spin in an infinite loop so they don't do any damage. - implementation of kernel spinlock - CONFIG_SMP and CONFIG_MAX_CPUS set by the build system 2010-09-15 16:09:52 +02:00			`#include "smp.h"`

			`unsigned ncpus;`
			`unsigned ht_per_core;`
			`unsigned bsp_cpu_id;`

			`struct cpu cpus[CONFIG_MAX_CPUS];`
SMP - Big kernel lock (BKL) - 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 2010-09-15 16:10:03 +02:00
			`SPINLOCK_DEFINE(big_kernel_lock)`