linux-kernel - [PATCH 00/11] Parallel CPU bringup for x86

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Date:   Thu,  9 Dec 2021 15:09:27 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        rcu@...r.kernel.org, mimoja@...oja.de, hewenliang4@...wei.com,
        hushiyuan@...wei.com, luolongjun@...wei.com, hejingxian@...wei.com
Subject: [PATCH 00/11] Parallel CPU bringup for x86_64

Dusting off this patch series from February, in which we reduce the time 
taken for bringing up CPUs on a 96-way Skylake box from 500ms to about 
34ms.

There is more parallelism to be had here, including a 1:many TSC sync 
(or just *no* TSC sync, in the kexec case), and letting the APs all run 
through their own states from CPUHP_BRINGUP_CPU to CPUHP_AP_ONLINE_IDLE 
in parallel too. But I'll take a mere factor of 15 for the time being.

We can also have a careful look at the remaining time spent in the 
initial INIT/SIPI phase and see what we can shave off it.

David Woodhouse (10):
      x86/apic/x2apic: Fix parallel handling of cluster_mask
      rcu: Kill rnp->ofl_seq and use only rcu_state.ofl_lock for exclusion
      rcu: Add mutex for rcu boost kthread spawning and affinity setting
      cpu/hotplug: Add dynamic parallel bringup states before CPUHP_BRINGUP_CPU
      x86/smpboot: Reference count on smpboot_setup_warm_reset_vector()
      x86/smpboot: Split up native_cpu_up into separate phases
      cpu/hotplug: Move idle_thread_get() to <linux/smpboot.h>
      x86/tsc: Avoid synchronizing TSCs with multiple CPUs in parallel
      x86/smp: Bring up secondary CPUs in parallel
      x86/kvm: Silence per-cpu pr_info noise about KVM clocks and steal time

Thomas Gleixner (1):
      x86/boot: Support parallel startup of secondary CPUs

 arch/x86/include/asm/realmode.h       |   3 +++
 arch/x86/include/asm/smp.h            |   9 ++++++-
 arch/x86/kernel/acpi/sleep.c          |   1 +
 arch/x86/kernel/apic/apic.c           |   2 +-
 arch/x86/kernel/apic/x2apic_cluster.c |  82 +++++++++++++++++++++++++++++++++++++-------------------------
 arch/x86/kernel/head_64.S             |  71 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/kvm.c                 |   6 ++---
 arch/x86/kernel/kvmclock.c            |   2 +-
 arch/x86/kernel/smpboot.c             | 243 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-------------------------------------------------
 arch/x86/kernel/tsc_sync.c            |   7 ++++++
 arch/x86/realmode/init.c              |   3 +++
 arch/x86/realmode/rm/trampoline_64.S  |  14 +++++++++++
 include/linux/cpuhotplug.h            |   2 ++
 include/linux/smpboot.h               |   7 ++++++
 kernel/cpu.c                          |  27 +++++++++++++++++++--
 kernel/rcu/tree.c                     |  65 ++++++++++++++++++++++++-------------------------
 kernel/rcu/tree.h                     |   7 +++---
 kernel/rcu/tree_plugin.h              |  10 ++++++--
 kernel/smpboot.c                      |   2 +-
 kernel/smpboot.h                      |   2 --
 20 files changed, 418 insertions(+), 147 deletions(-)