linux-kernel - Re: [RFC 2/2] Make x86 calibrate

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Message-ID: <4D948EC1.9080208@kernel.org>
Date:	Thu, 31 Mar 2011 07:25:05 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Robin Holt <holt@....com>
CC:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [RFC 2/2] Make x86 calibrate_delay run in parallel.

On 03/31/2011 02:29 AM, Robin Holt wrote:
...
> I don't see how this patch would affect that.  Has this been tested on
> a multi-core intel cpu?  I will try to test it today when I get to the
> office.

Yes. I tested on our 8 sockets 10 cores intel cpu system and 8 cores system.
looks getting correct result.

>
> Additionally, it takes the bogomips value from being part of an output
> line and makes it a separate line.  On a 4096 cpu system, that will mean
> many additional lines of output.  In the past, we have seen that will
> cause a considerable slowdown as time is spent printing.  Fortunately,
> that is likely not going to slow things down as a secondary cpu will
> likely be doing that work while the boot cpu is allowed to continue with
> the boot.  Is there really a value for a normal boot to have this output?
> Can we remove the individual lines of output and just print the system
> BogoMips value?

that is easy. just update print_lpj.

static void __cpuinit print_lpj(int cpu, char *str, unsigned long lpj)
{
         static bool printed;

         if (printed)
                 return;

         pr_info("CPU%d: Calibrating delay%s"
                 "%lu.%02lu BogoMIPS (lpj=%lu)\n", cpu, str,
                 lpj/(500000/HZ), (lpj/(5000/HZ)) % 100, lpj);

         /* only print cpu0, and cpu1 */
         if (cpu)
                 printed = true;
}

current printing is for debug purpose, So we don't need to waiting the booting get done.
just checking it serial console.

Thanks

Yinghai
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