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Subject: Re: [PATCH 1/2] x86-64 TIF flags for debug regs and io bitmap in
	ctxsw
From: Arjan van de Ven <arjan@infradead.org>
To: eranian@hpl.hp.com
Cc: linux-kernel@vger.kernel.org, ak@suse.de
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Date: Tue, 04 Jul 2006 09:51:49 +0200
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> -		}
> -	}
> +	if (unlikely((task_thread_info(next_p)->flags & _TIF_WORK_CTXSW))
> +	    || test_tsk_thread_flag(prev_p, TIF_IO_BITMAP))
> +		__switch_to_xtra(prev_p, next_p, tss);

well isn't this replacing an if() (which isn't cheap but also not
expensive, due to unlikely()) with an atomic operation (which *is*
expensive) ?

That to me doesn't make this sound like an actual win....