linux-kernel - [PATCH v4 0/9] Parallel CPU bringup for x86

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Date:   Tue,  1 Feb 2022 20:53:19 +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,
        Tom Lendacky <thomas.lendacky@....com>,
        Sean Christopherson <seanjc@...gle.com>,
        Paul Menzel <pmenzel@...gen.mpg.de>
Subject: [PATCH v4 0/9] Parallel CPU bringup for x86_64

Doing the INIT/SIPI/SIPI in parallel for all APs and *then* waiting for
them shaves about 80% off the AP bringup time on a 96-thread 2-socket
Skylake box (EC2 c5.metal) — from about 500ms to 100ms.

There are more wins to be had with further parallelisation, but this is
the simple part.

v2: Cut it back to just INIT/SIPI/SIPI in parallel for now, nothing more
v3: Clean up x2apic patch, add MTRR optimisation, lock topology update
    in preparation for more parallelisation.
v4: Fixes to the real mode parallelisation patch spotted by SeanC, to
    avoid scribbling on initial_gs in common_cpu_up(), and to allow all
    24 bits of the physical X2APIC ID to be used. That patch still needs
    a Signed-off-by from its original author, who once claimed not to
    remember writing it at all. But now we've fixed it, hopefully he'll
    admit it now :)

David Woodhouse (8):
      x86/apic/x2apic: Fix parallel handling of cluster_mask
      cpu/hotplug: Move idle_thread_get() to <linux/smpboot.h>
      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 and document them
      x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel
      x86/mtrr: Avoid repeated save of MTRRs on boot-time CPU bringup
      x86/smpboot: Serialize topology updates for secondary bringup

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

[dwoodhou@i7 linux-2.6]$ git diff --stat  v5.17-rc2..share/parallel-5.17-part1 
 arch/x86/include/asm/realmode.h       |   3 +
 arch/x86/include/asm/smp.h            |  13 +-
 arch/x86/include/asm/topology.h       |   2 -
 arch/x86/kernel/acpi/sleep.c          |   1 +
 arch/x86/kernel/apic/apic.c           |   2 +-
 arch/x86/kernel/apic/x2apic_cluster.c | 108 ++++++-----
 arch/x86/kernel/cpu/common.c          |   6 +-
 arch/x86/kernel/cpu/mtrr/mtrr.c       |   9 +
 arch/x86/kernel/head_64.S             |  73 ++++++++
 arch/x86/kernel/smpboot.c             | 325 ++++++++++++++++++++++++----------
 arch/x86/realmode/init.c              |   3 +
 arch/x86/realmode/rm/trampoline_64.S  |  14 ++
 arch/x86/xen/smp_pv.c                 |   4 +-
 include/linux/cpuhotplug.h            |   2 +
 include/linux/smpboot.h               |   7 +
 kernel/cpu.c                          |  27 ++-
 kernel/smpboot.c                      |   2 +-
 kernel/smpboot.h                      |   2 -
 18 files changed, 442 insertions(+), 161 deletions(-)