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From: Andy Lutomirski <luto@amacapital.net>
Date: Thu, 7 Apr 2016 17:13:40 -0700
Message-ID: <CALCETrWzS0MGTtDLecuwZa4ikvGAYHwWf-4gDjti=DV6gb1V+g@mail.gmail.com>
Subject: Re: [PATCH] x86/hpet: Reduce HPET counter read contention
To: Waiman Long <waiman.long@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        X86 ML <x86@kernel.org>, Jiang Liu <jiang.liu@linux.intel.com>,
        Borislav Petkov <bp@suse.de>, Andy Lutomirski <luto@kernel.org>,
        Scott J Norton <scott.norton@hpe.com>,
        Douglas Hatch <doug.hatch@hpe.com>, Randy Wright <rwright@hpe.com>
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On Thu, Apr 7, 2016 at 8:07 AM, Waiman Long <waiman.long@hpe.com> wrote:
> On 04/07/2016 12:58 AM, Andy Lutomirski wrote:
>> Reading the HPET is so slow that all the atomic ops in the world won't
>> make a dent.  Why not just turn this optimization on unconditionally?
>>
>> --Andy
>
>
> I am constantly on the alert that we should not introduce regression on
> lesser systems like a single socket machine with a few cores. That is why I
> put the check to conditionally enable this optimization. I have no issue of
> taking that out and let it be the default as long as no one object.
>

Agreed.  I just suspect it's actually faster on all systems.

This reminds me -- I need to send out my patch to disable the vdso
HPET code, which will make your change more effective.  I'll cc you.

> Cheers,
> Longman


-- 
Andy Lutomirski
AMA Capital Management, LLC