Messages in this thread | | | Date | Wed, 1 Feb 2023 14:40:09 +0000 | Subject | Re: [PATCH v4 0/9] Parallel CPU bringup for x86_64 | From | Usama Arif <> |
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On 01/02/2022 20:53, David Woodhouse wrote: > 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. >
Hi,
We are interested in reducing the boot time of servers (with kexec), and smpboot takes up a significant amount of time while booting. When testing the patch series (rebased to v6.1) on a server with 128 CPUs split across 2 NUMA nodes, it brought down the smpboot time from ~700ms to 100ms. Adding another cpuhp state for do_wait_cpu_initialized to make sure cpu_init is reached (as done in v1 of the series + using the cpu_finishup_mask) brought it down further to ~30ms.
I just wanted to check what was needed to progress the patch series further for review? There weren't any comments on v4 of the patch so I couldn't figure out what more is needed. I think its quite useful to have this working so would be really glad help in anything needed to restart the review.
Thanks! Usama
> 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(-) > > > >
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