linux-kernel - Re: [External] Re: [PATCH v6 00/11] Parallel CPU bringup for x86

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Date:   Mon, 6 Feb 2023 12:18:00 +0000
From:   Usama Arif <usama.arif@...edance.com>
To:     David Woodhouse <dwmw2@...radead.org>, Russ Anderson <rja@....com>
Cc:     tglx@...utronix.de, arjan@...ux.intel.com, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com,
        x86@...nel.org, pbonzini@...hat.com, paulmck@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        rcu@...r.kernel.org, mimoja@...oja.de, hewenliang4@...wei.com,
        thomas.lendacky@....com, seanjc@...gle.com, pmenzel@...gen.mpg.de,
        fam.zheng@...edance.com, punit.agrawal@...edance.com,
        simon.evans@...edance.com, liangma@...ngbit.com
Subject: Re: [External] Re: [PATCH v6 00/11] Parallel CPU bringup for x86_64



On 06/02/2023 08:28, David Woodhouse wrote:
> On Sun, 2023-02-05 at 13:17 -0600, Russ Anderson wrote:
>>
>> Gave the v6 patchset a try on a system with 1920 logocal cpus
>> (sixteen 60 core Sapphire Rapids sockets with Hyperthreadding
>> enabled).
>>
>> 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.  That is impressive.
>>
>> 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/parallel-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.

I think it would be interesting to get the numbers for such a big 
machine for 3 cases: part1, part1+reuse timer calibration and part1+part2.

Russ mentioned testing v6, so I guess the above numbers are for 
part1+reuse timer calibration.

For my machine the smpboot times were:

No patches: 700ms
part 1:100ms
part1+reuse timer calibration: 30ms
part1+part2: 30ms

Thanks,
Usama