Message-ID: <3b626936ccc4d5123cb9113378bec6f77182def3.camel@infradead.org>
Subject: Re: [PATCH v6 00/11] Parallel CPU bringup for x86_64
From:   David Woodhouse <dwmw2@infradead.org>
To:     Russ Anderson <rja@hpe.com>, Usama Arif <usama.arif@bytedance.com>
Cc:     tglx@linutronix.de, 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
Date:   Mon, 06 Feb 2023 08:28:34 +0000
In-Reply-To: <20230205191734.GA6027@hpe.com>
References: <20230202215625.3248306-1-usama.arif@bytedance.com>
         <20230205191734.GA6027@hpe.com>
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On Sun, 2023-02-05 at 13:17 -0600, Russ Anderson wrote:
>=20
> Gave the v6 patchset a try on a system with 1920 logocal cpus
> (sixteen 60 core Sapphire Rapids sockets with Hyperthreadding
> enabled).
>=20
> Without the patchset it took 71 seconds to start all the cpus.
> With the v6 patchset it took 14 seconds to start all the cpus,
> a reduction of 57 seconds.=C2=A0 That is impressive.
>=20
> Full boot, to root login prompt, without patches takes 223 seconds.
> This patchset reduces the full boot time by 57 seconds, a 25%
> reduction.

Nice; thanks for testing.

Is that with just the "part1" patch series which has been posted, or
also with the 'parallel part 2' still taking shape in the tree at
https://git.infradead.org/users/dwmw2/linux.git/shortlog/refs/heads/paralle=
l-6.2-rc6

I believe Usama said the second phase of parallelism didn't really help
much in terms of overall timing? Confirming that *without* all the
debug prints would be interesting. And we can look for what still
*could* be made parallel.

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