Re: [PATCH v9 0/8] Parallel CPU bringup for x86_64

From: Oleksandr Natalenko
Date: Mon Feb 20 2023 - 11:08:44 EST


Hello.

On středa 15. února 2023 15:54:17 CET Usama Arif wrote:
> The main change over v8 is dropping the patch to avoid repeated saves of MTRR
> at boot time. It didn't make a difference to smpboot time and is independent
> of parallel CPU bringup, so if needed can be explored in a separate patchset.
>
> The patches have also been rebased to v6.2-rc8 and retested and the
> improvement in boot time is the same as v8.
>
> Thanks,
> Usama
>
> Changes across versions:
> 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 :)
> v5: rebase to v6.1 and remeasure performance, disable parallel bringup
> for AMD CPUs.
> v6: rebase to v6.2-rc6, disabled parallel boot on amd as a cpu bug and
> reused timer calibration for secondary CPUs.
> v7: [David Woodhouse] iterate over all possible CPUs to find any existing
> cluster mask in alloc_clustermask. (patch 1/9)
> Keep parallel AMD support enabled in AMD, using APIC ID in CPUID leaf
> 0x0B (for x2APIC mode) or CPUID leaf 0x01 where 8 bits are sufficient.
> Included sanity checks for APIC id from 0x0B. (patch 6/9)
> Removed patch for reusing timer calibration for secondary CPUs.
> commit message and code improvements.
> v8: Fix CPU0 hotplug by setting up the initial_gs, initial_stack and
> early_gdt_descr.
> Drop trampoline lock and bail if APIC ID not found in find_cpunr.
> Code comments improved and debug prints added.
> v9: Drop patch to avoid repeated saves of MTRR at boot time.
> rebased and retested at v6.2-rc8.
> added kernel doc for no_parallel_bringup and made do_parallel_bringup
> __ro_after_init.
>
> David Woodhouse (8):
> x86/apic/x2apic: Allow CPU cluster_mask to be populated in parallel
> 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: Support parallel startup of secondary CPUs
> x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel
> x86/smpboot: Serialize topology updates for secondary bringup
>
> .../admin-guide/kernel-parameters.txt | 3 +
> arch/x86/include/asm/realmode.h | 3 +
> arch/x86/include/asm/smp.h | 14 +-
> 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 | 130 ++++---
> arch/x86/kernel/cpu/common.c | 6 +-
> arch/x86/kernel/head_64.S | 99 ++++-
> arch/x86/kernel/smpboot.c | 350 +++++++++++++-----
> 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 | 31 +-
> kernel/smpboot.c | 2 +-
> kernel/smpboot.h | 2 -
> 18 files changed, 515 insertions(+), 160 deletions(-)

I've applied this to the v6.2 kernel, and suspend/resume broke on my Ryzen 5950X desktop. The machine suspends just fine, but on resume the screen stays blank, and there's no visible disk I/O.

Reverting the series brings suspend/resume back to working state.

--
Oleksandr Natalenko (post-factum)