From: David Woodhouse <dwmw2@infradead.org>
To: Usama Arif <usama.arif@bytedance.com>,
tglx@linutronix.de, kim.phillips@amd.com
Cc: arjan@linux.intel.com, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, hpa@zytor.com, x86@kernel.org,
pbonzini@redhat.com, paulmck@kernel.org,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
rcu@vger.kernel.org, mimoja@mimoja.de, hewenliang4@huawei.com,
thomas.lendacky@amd.com, seanjc@google.com,
pmenzel@molgen.mpg.de, fam.zheng@bytedance.com,
punit.agrawal@bytedance.com, simon.evans@bytedance.com,
liangma@liangbit.com
Subject: Re: [PATCH v9 0/8] Parallel CPU bringup for x86_64
Date: Wed, 22 Feb 2023 10:11:05 +0000 [thread overview]
Message-ID: <62ee53770b4010f065346b7f2a1200013836be97.camel@infradead.org> (raw)
In-Reply-To: <20230215145425.420125-1-usama.arif@bytedance.com>
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On Wed, 2023-02-15 at 14:54 +0000, 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 for picking this up, Usama.
So the next thing that might be worth looking at is allowing the APs
all to be running their hotplug thread simultaneously, bringing
themselves from CPUHP_BRINGUP_CPU to CPUHP_AP_ONLINE. This series eats
the initial INIT/SIPI/SIPI latency, but if there's any significant time
in the AP hotplug thread, that could be worth parallelising.
There may be further wins in the INIT/SIPI/SIPI too. Currently we
process each CPU at a time, sending INIT, SIPI, waiting 10µs and
sending another SIPI.
What if we sent the first INIT+SIPI to all CPUs, then did another pass
sending another SIPI only to those which hadn't already started running
and set their bit in cpu_initialized_mask ?
Might not be worth it, and there's an added complexity that they all
have to wait for each other (on the real mode trampoline lock) before
they can take their turn and get as far as setting their bit in
cpu_initialized_mask. So we'd probably end up sending the second SIPI
to most of them *anyway*.
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next prev parent reply other threads:[~2023-02-22 10:11 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-15 14:54 [PATCH v9 0/8] Parallel CPU bringup for x86_64 Usama Arif
2023-02-15 14:54 ` [PATCH v9 1/8] x86/apic/x2apic: Allow CPU cluster_mask to be populated in parallel Usama Arif
2023-02-16 20:58 ` Kim Phillips
2023-02-15 14:54 ` [PATCH v9 2/8] cpu/hotplug: Move idle_thread_get() to <linux/smpboot.h> Usama Arif
2023-02-15 14:54 ` [PATCH v9 3/8] cpu/hotplug: Add dynamic parallel bringup states before CPUHP_BRINGUP_CPU Usama Arif
2023-02-15 14:54 ` [PATCH v9 4/8] x86/smpboot: Reference count on smpboot_setup_warm_reset_vector() Usama Arif
2023-02-15 14:54 ` [PATCH v9 5/8] x86/smpboot: Split up native_cpu_up into separate phases and document them Usama Arif
2023-02-15 14:54 ` [PATCH v9 6/8] x86/smpboot: Support parallel startup of secondary CPUs Usama Arif
2023-02-15 14:54 ` [PATCH v9 7/8] x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel Usama Arif
2023-02-15 14:54 ` [PATCH v9 8/8] x86/smpboot: Serialize topology updates for secondary bringup Usama Arif
2023-02-16 6:34 ` [PATCH v9 0/8] Parallel CPU bringup for x86_64 Paul E. McKenney
2023-02-20 16:08 ` Oleksandr Natalenko
2023-02-20 16:20 ` David Woodhouse
2023-02-20 16:40 ` Oleksandr Natalenko
2023-02-20 20:31 ` David Woodhouse
2023-02-20 21:23 ` Oleksandr Natalenko
2023-02-20 21:34 ` Piotr Gorski
2023-02-20 21:39 ` David Woodhouse
2023-02-20 23:23 ` Kim Phillips
2023-02-20 23:30 ` David Woodhouse
2023-02-21 4:20 ` Kim Phillips
2023-02-21 7:16 ` David Woodhouse
2023-02-21 7:27 ` Oleksandr Natalenko
2023-02-21 7:53 ` David Woodhouse
2023-02-21 8:05 ` Oleksandr Natalenko
2023-02-21 8:17 ` David Woodhouse
2023-02-21 8:25 ` Oleksandr Natalenko
2023-02-21 8:35 ` David Woodhouse
2023-02-21 8:44 ` Oleksandr Natalenko
2023-02-21 9:06 ` David Woodhouse
2023-02-21 9:49 ` Oleksandr Natalenko
2023-02-21 10:27 ` David Woodhouse
2023-02-21 10:47 ` [External] " Usama Arif
2023-02-21 11:42 ` Oleksandr Natalenko
2023-02-21 11:54 ` Usama Arif
2023-02-21 13:22 ` David Woodhouse
2023-02-21 11:46 ` Oleksandr Natalenko
2023-02-21 11:49 ` David Woodhouse
2023-02-21 12:14 ` Oleksandr Natalenko
2023-02-21 19:10 ` David Woodhouse
2023-02-21 20:04 ` [External] " Usama Arif
2023-02-21 21:04 ` Oleksandr Natalenko
2023-02-21 21:41 ` Thomas Gleixner
2023-02-21 21:44 ` David Woodhouse
2023-02-21 23:18 ` David Woodhouse
2023-02-22 0:00 ` [External] " Usama Arif
2023-02-22 8:19 ` David Woodhouse
2023-02-22 9:46 ` Thomas Gleixner
2023-02-22 9:51 ` David Woodhouse
2023-02-22 9:31 ` Thomas Gleixner
2023-02-20 22:22 ` Piotr Gorski
2023-02-20 22:23 ` [External] " Usama Arif
2023-02-20 22:41 ` Oleksandr Natalenko
2023-02-22 10:11 ` David Woodhouse [this message]
2023-02-22 11:11 ` Usama Arif
2023-02-22 12:08 ` Brian Gerst
2023-02-22 12:53 ` David Woodhouse
2023-02-22 16:42 ` Thomas Gleixner
2023-02-23 11:07 ` David Woodhouse
2023-02-23 14:37 ` Thomas Gleixner
2023-02-23 15:12 ` David Woodhouse
2023-02-23 19:24 ` [External] " Usama Arif
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