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From: Nicolai Stange <nicstange@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Nicolai Stange <nicstange@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Borislav Petkov <bp@suse.de>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>,
	Len Brown <len.brown@intel.com>,
	"Christopher S. Hall" <christopher.s.hall@intel.com>,
	Adrian Hunter <adrian.hunter@intel.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/3] arch, x86, tsc deadline clockevent dev: reduce frequency roundoff error
Date: Wed, 13 Jul 2016 16:31:51 +0200	[thread overview]
Message-ID: <8737ndtxrc.fsf@gmail.com> (raw)
In-Reply-To: <fe5b1c72-2371-bdaa-3f56-dd6e49368d35@redhat.com> (Paolo Bonzini's message of "Wed, 13 Jul 2016 15:51:57 +0200")

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 13/07/2016 15:49, Peter Zijlstra wrote:
>> On Wed, Jul 13, 2016 at 03:03:42PM +0200, Nicolai Stange wrote:
>> 
>>>  		clockevents_config_and_register(levt,
>>> +						(u32)(((u64)tsc_khz * 1000) /
>>> +							TSC_DIVISOR),
>>>  						0xF, ~0UL);
>> 
>> div_u64() perhaps ?
>
> Or just squash together the two patches and do
>
> 	tsc_khz * (1000 / TSC_DIVISOR)
>
> because with TSC_DIVISOR equal to 2/4/8 there is no error from
> reassociating the operation.

Oh great, I didn't see this. Will resend.

Thanks,

Nicolai

  reply	other threads:[~2016-07-13 14:32 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-13 13:03 [PATCH v3 0/3] reduce TSC deadline frequency errors Nicolai Stange
2016-07-13 13:03 ` [PATCH v3 1/3] arch, x86, tsc deadline clockevent dev: reduce frequency roundoff error Nicolai Stange
2016-07-13 13:49   ` Peter Zijlstra
2016-07-13 13:51     ` Paolo Bonzini
2016-07-13 14:31       ` Nicolai Stange [this message]
2016-07-13 13:03 ` [PATCH v3 2/3] arch, x86, tsc deadline clockevent dev: reduce TSC_DIVISOR to 2 Nicolai Stange
2016-07-13 13:03 ` [PATCH v3 3/3] arch, x86, tsc: inform TSC deadline clockevent device about recalibration Nicolai Stange

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