linux-kernel - Re: [PATCH 4/7] perf: Check if HT is supported and enabled

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Message-ID: <4D236E47.5080500@zytor.com>
Date:	Tue, 04 Jan 2011 11:00:23 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	Stephane Eranian <eranian@...gle.com>,
	Lin Ming <ming.m.lin@...el.com>, Ingo Molnar <mingo@...e.hu>,
	Andi Kleen <andi@...stfloor.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/7] perf: Check if HT is supported and enabled

On 01/04/2011 05:58 AM, Peter Zijlstra wrote:
> On Tue, 2011-01-04 at 14:52 +0100, Stephane Eranian wrote:
>>
>> Couldn't you simply over-provision, and then when the CPU is online, use my
>> ht_enabled statement to figure out whether or not you need to handle the sharing
>> issue? 
> 
> That's pretty much what Lin's latest does:
> 
>  X86_FEATURE_HT && smp_num_siblings > 1
> 
> shows the CPU is capable of HT and will allocate the needed resources.
> 

>From the sound of it, it doesn't seem like it's worth optimizing out the
fairly small memory allocation.

	-hpa

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