Message-ID: <4AB903E6.6030208@redhat.com>
Date: Tue, 22 Sep 2009 20:05:42 +0300
From: Avi Kivity <avi@redhat.com>
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To: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Ingo Molnar <mingo@elte.hu>, "H. Peter Anvin" <hpa@zytor.com>,
       linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
       Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH v2] core, x86: Add user return notifiers
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On 09/22/2009 07:55 PM, Peter Zijlstra wrote:
>> If you're using lockdep, surely that's not your biggest worry?
>>      
> No, but that's all under #ifdef and fully disappears when not enabled.
> Generic return-tu-user notifiers don't sound like they will though.
>    

They will if not selected.  If selected and not armed, they will have 
zero runtime impact since they piggyback on existing branches 
(_TIF_DO_NOTIFY_MASK and near relatives).  If selected and armed they'll 
cause __switch_to_xtra() on every context switch and do_notity_resume() 
on syscall exit until disarmed, but then you've asked for it.

-- 
error compiling committee.c: too many arguments to function

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