Re: [PATCH 1/2] x86-64 TIF flags for debug regs and io bitmap inctxsw

[Arjan van de Ven]

> -		}
> -	}
> +	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....


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