linux-kernel - Re: [PATCH v3 0/9] Parallel CPU bringup for x86

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Date:   Tue, 28 Dec 2021 12:34:25 +0100
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     David Woodhouse <dwmw2@...radead.org>,
        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: Re: [PATCH v3 0/9] Parallel CPU bringup for x86_64

Dear David,


Am 27.12.21 um 17:57 schrieb Paul Menzel:

> Am 15.12.21 um 15:56 schrieb David Woodhouse:
>> 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 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.
>>
>>
>> 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
>>
>>   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             |  71 ++++++++
>>   arch/x86/kernel/smpboot.c             | 324 ++++++++++++++++++++++++----------
>>   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, 441 insertions(+), 159 deletions(-)
> 
> Thank you for working on this. I tested this on a MSI MS-7A37/B350M 
> MORTAR (BIOS 1.MW 11/01/2021) with a Ryzen 3 2200G, but nothing was 
> printed to the screen after the GRUB loading messages, so it crashed or 
> hung somewhere. Unfortunately, this device is used by others, and no 
> serial console is connected and I do not know how to capture the Linux 
> log with other means.

Same on the ASUS F2A85-M PRO with AMD A6-6400K. Without serial console, 
the messages below are printed below to the monitor after nine seconds.

      [    1.078879] smp: Bringing up secondary CPUs ...
      [    1.080950] x86: Booting SMP configuration:

Please find the serial log attached.


Kind regards,

Paul
View attachment "linux-5.16-rc6-messages.txt" of type "text/plain" (14242 bytes)