Messages in this thread | | | From | "Fenghua Yu" <> | Subject | [PATCH 0/6] x86/cpu hotplug: Wake up offline CPU via mwait or nmi | Date | Mon, 4 Jun 2012 11:17:49 -0700 |
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From: Fenghua Yu <fenghua.yu@intel.com>
Since offline CPU is in wmait or hlt if mwait feature is not available, it can be waken up by writing to monitored memory range or via nmi.
Compared to current INIT, INIT, STARTUP wake up sequence, waking up offline CPU is faster via wmait or nmi. This is especially useful when offline CPU for power saving and shorter waking up time is desired. On one tested desktop machine, waking up time via mwait or nmi is reduced to 23% of waking up time via INIT. Waking up time is measured from the beginning of store_online() to the beginning of cpu_idle() after the CPU is waken up.
Waking up offline CPU via mwait or nmi is also useful to support BSP offline/ online because offline BSP can not be waken up by the INIT's sequence. The BSP offline/online patchset will be sent out seperately.
Fenghua Yu (6): x86/Documentation/kernel-parameters.txt: Add wakeup_cpu_via_init kernel parameter help x86/head_32.S/head_64.S: Kernel entry code after waking up offline CPU via mwait or nmi x86/smpboot.c: Wake up offline CPU via mwait or nmi x86/apic_flat_64.c: Wakeup function in apic calls mwait or nmi method x86/x2apic_cluster.c: Wakeup function in x2apic_cluster calls mwait or nmi method x86/x2apic_phys.c: Wakeup function in x2apic_phys calls mwait or nmi method
Documentation/kernel-parameters.txt | 3 + arch/x86/include/asm/apic.h | 5 +- arch/x86/include/asm/cpu.h | 1 + arch/x86/kernel/apic/apic_flat_64.c | 2 + arch/x86/kernel/apic/x2apic_cluster.c | 1 + arch/x86/kernel/apic/x2apic_phys.c | 1 + arch/x86/kernel/head_32.S | 12 ++ arch/x86/kernel/head_64.S | 14 +++ arch/x86/kernel/smpboot.c | 187 ++++++++++++++++++++++++++++----- 9 files changed, 198 insertions(+), 28 deletions(-)
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