a157e42516
The main goal of this is to generate timer interrupts only when there is some work to do. When CPU is busy interrupts are generating at full rate of hz + stathz to fullfill scheduler and timekeeping requirements. But when CPU is idle, only minimum set of interrupts (down to 8 interrupts per second per CPU now), needed to handle scheduled callouts is executed. This allows significantly increase idle CPU sleep time, increasing effect of static power-saving technologies. Also it should reduce host CPU load on virtualized systems, when guest system is idle. There is set of tunables, also available as writable sysctls, allowing to control wanted event timer subsystem behavior: kern.eventtimer.timer - allows to choose event timer hardware to use. On x86 there is up to 4 different kinds of timers. Depending on whether chosen timer is per-CPU, behavior of other options slightly differs. kern.eventtimer.periodic - allows to choose periodic and one-shot operation mode. In periodic mode, current timer hardware taken as the only source of time for time events. This mode is quite alike to previous kernel behavior. One-shot mode instead uses currently selected time counter hardware to schedule all needed events one by one and program timer to generate interrupt exactly in specified time. Default value depends of chosen timer capabilities, but one-shot mode is preferred, until other is forced by user or hardware. kern.eventtimer.singlemul - in periodic mode specifies how much times higher timer frequency should be, to not strictly alias hardclock() and statclock() events. Default values are 2 and 4, but could be reduced to 1 if extra interrupts are unwanted. kern.eventtimer.idletick - makes each CPU to receive every timer interrupt independently of whether they busy or not. By default this options is disabled. If chosen timer is per-CPU and runs in periodic mode, this option has no effect - all interrupts are generating. As soon as this patch modifies cpu_idle() on some platforms, I have also refactored one on x86. Now it makes use of MONITOR/MWAIT instrunctions (if supported) under high sleep/wakeup rate, as fast alternative to other methods. It allows SMP scheduler to wake up sleeping CPUs much faster without using IPI, significantly increasing performance on some highly task-switching loads. Tested by: many (on i386, amd64, sparc64 and powerc) H/W donated by: Gheorghe Ardelean Sponsored by: iXsystems, Inc.
46 lines
1.2 KiB
C
46 lines
1.2 KiB
C
/*-
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* ----------------------------------------------------------------------------
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* "THE BEER-WARE LICENSE" (Revision 42):
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* <phk@FreeBSD.org> wrote this file. As long as you retain this notice you
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* can do whatever you want with this stuff. If we meet some day, and you think
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* this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
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* ----------------------------------------------------------------------------
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*
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* from: src/sys/alpha/include/smp.h,v 1.8 2005/01/05 20:05:50 imp
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* JNPR: smp.h,v 1.3 2006/12/02 09:53:41 katta
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* $FreeBSD$
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*
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*/
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#ifndef _MACHINE_SMP_H_
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#define _MACHINE_SMP_H_
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#ifdef _KERNEL
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#include <machine/pcb.h>
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/*
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* Interprocessor interrupts for SMP.
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*/
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#define IPI_RENDEZVOUS 0x0002
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#define IPI_AST 0x0004
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#define IPI_STOP 0x0008
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#define IPI_STOP_HARD 0x0008
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#define IPI_PREEMPT 0x0010
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#define IPI_HARDCLOCK 0x0020
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#ifndef LOCORE
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void ipi_all_but_self(int ipi);
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void ipi_cpu(int cpu, u_int ipi);
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void ipi_selected(cpumask_t cpus, int ipi);
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void smp_init_secondary(u_int32_t cpuid);
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void mpentry(void);
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extern struct pcb stoppcbs[];
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#endif /* !LOCORE */
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#endif /* _KERNEL */
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#endif /* _MACHINE_SMP_H_ */
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